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Troubleshooting RXTX 6.3

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  • g8xul
    I m having trouble with the simplest element of the RXTX6.3 transmitter section and would appreciate some help before I start pulling out components. The RX
    Message 1 of 29 , Sep 23, 2008
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      I'm having trouble with the simplest element of the RXTX6.3
      transmitter section and would appreciate some help before I start
      pulling out components.

      The RX seems to work fine. I've checked soldering and component
      values under magnification. I used good ESD practice throughout
      construction.

      The problem is with the PTT section. Construction of the main board
      is complete and I'm testing without the PA daughter board installed.
      My original problem was that when testing the PA module The current
      draw exceeded my 150mA current limit, knocking the supply voltage
      down to a couple of volts. I decided to check the voltages at J1 /
      J2 before faulting the PA board.

      On power up the current draw is ~95mA @ 7.047 center frequency. With
      a DMM I measure:

      PTT IN 0V
      /PTT IN ~10.5V
      S12V 0V

      PTT IN was then connected to 12V (Cathode D1). Readings now:

      /PTT IN 0V
      S12V ~11.8V

      PTT IN back to 0V (connected to ground). Readings now:

      /PTT IN ~ 5.8V
      S12V ~11.8V

      S12V seems to have 'latched' at 11.8V. It remains at 11.8V
      indefinately - irrespective of changes to PTT untill the power is
      removed. The readings above can then be reproduced.

      Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish (the
      value given in the detailed contruction notes)?

      Any help much appreciated.

      73, Dave
    • Mike Collins
      ... Hi Dave, Yes, S12V should follow PTT IN. Q1 and Q2 both act as an inversion. The only way for /PTT IN to be lower than 12-0.7V is for Q1 to be somewhat
      Message 2 of 29 , Sep 23, 2008
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        > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish (the
        > value given in the detailed contruction notes)?

        Hi Dave,

        Yes, S12V should follow PTT IN. Q1 and Q2 both act as an inversion.

        The only way for /PTT IN to be lower than 12-0.7V is for Q1 to be
        somewhat ON. For Q1 to be on: the Q1 BE must be above .6V or so. I
        would measure across R20 next time it latches up.

        R20 is used to drain the voltage on the C27 (at .7V when Q1 ON) down
        to help turn off Q1. With no PTTIN voltage the R20 voltage should be
        at 0 V.

        Q1 turns on when the PTT IN start going above 1.2V or so. This
        happens when the R19/R20 divider starts to go higher than .6V; when
        the BE junction starts turning on. When fully on Q1 collector should
        be at about .2 V or so.

        Q2 does about the opposite: when /PTTIN goes low; the BE junction of
        Q2 turns on (at about 12V-0.6V) and then S12V goes close to 12V (i.e.
        12V - 0.2V).

        73, Mike Collins KF4BQ
      • Leonard
        ... board ... installed. ... current ... J1 / ... With ... (the ... You probably have it fixed by now but I have a partial troubleshooting page on that section
        Message 3 of 29 , Sep 24, 2008
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          --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
          >
          > I'm having trouble with the simplest element of the RXTX6.3
          > transmitter section and would appreciate some help before I start
          > pulling out components.
          >
          > The RX seems to work fine. I've checked soldering and component
          > values under magnification. I used good ESD practice throughout
          > construction.
          >
          > The problem is with the PTT section. Construction of the main
          board
          > is complete and I'm testing without the PA daughter board
          installed.
          > My original problem was that when testing the PA module The
          current
          > draw exceeded my 150mA current limit, knocking the supply voltage
          > down to a couple of volts. I decided to check the voltages at
          J1 /
          > J2 before faulting the PA board.
          >
          > On power up the current draw is ~95mA @ 7.047 center frequency.
          With
          > a DMM I measure:
          >
          > PTT IN 0V
          > /PTT IN ~10.5V
          > S12V 0V
          >
          > PTT IN was then connected to 12V (Cathode D1). Readings now:
          >
          > /PTT IN 0V
          > S12V ~11.8V
          >
          > PTT IN back to 0V (connected to ground). Readings now:
          >
          > /PTT IN ~ 5.8V
          > S12V ~11.8V
          >
          > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
          > indefinately - irrespective of changes to PTT untill the power is
          > removed. The readings above can then be reproduced.
          >
          > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish
          (the
          > value given in the detailed contruction notes)?
          >
          > Any help much appreciated.
          >
          > 73, Dave
          >

          You probably have it fixed by now but I have a partial
          troubleshooting page on that section at

          http://golddredgervideo.com/kc0wox/softrock/tx/misc.htm

          I haven't finished it yet but it goes through much of the switching
          part.
          Leonard
        • Leonard
          ... Opps! My page is for a 6.2, not a 6.3. Too many versions out. Leonard
          Message 4 of 29 , Sep 24, 2008
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            --- In softrock40@yahoogroups.com, "Leonard" <dredger@...> wrote:
            >
            > You probably have it fixed by now but I have a partial
            > troubleshooting page on that section at
            >
            > http://golddredgervideo.com/kc0wox/softrock/tx/misc.htm
            >
            > I haven't finished it yet but it goes through much of the switching
            > part.
            > Leonard
            >


            Opps!

            My page is for a 6.2, not a 6.3. Too many versions out.
            Leonard
          • singhpk99
            Hi Dave, Is the value of R21 in yr 6.3 rxtx 49.9 ohm(gold band) instead of 4.9k? Your Q2 may be toast also . Please use a multimeter to check resistances and
            Message 5 of 29 , Sep 24, 2008
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              Hi Dave,

              Is the value of R21 in yr 6.3 rxtx 49.9 ohm(gold band) instead of
              4.9k? Your Q2 may be toast also . Please use a multimeter to check
              resistances and continuity with power off around Q2 and Q1 .
              Dont rule out a dry solder joint either- PTH vias can be open at times
              also.

              I am just compelting my rxtx6.3 also - have to build the filter
              modules and the PA yet.

              73s
              ab2xf
              --- In softrock40@yahoogroups.com, "Leonard" <dredger@...> wrote:
              >
              > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
              > >
              > > I'm having trouble with the simplest element of the RXTX6.3
              > > transmitter section and would appreciate some help before I start
              > > pulling out components.
              > >
              > > The RX seems to work fine. I've checked soldering and component
              > > values under magnification. I used good ESD practice throughout
              > > construction.
              > >
              > > The problem is with the PTT section. Construction of the main
              > board
              > > is complete and I'm testing without the PA daughter board
              > installed.
              > > My original problem was that when testing the PA module The
              > current
              > > draw exceeded my 150mA current limit, knocking the supply voltage
              > > down to a couple of volts. I decided to check the voltages at
              > J1 /
              > > J2 before faulting the PA board.
              > >
              > > On power up the current draw is ~95mA @ 7.047 center frequency.
              > With
              > > a DMM I measure:
              > >
              > > PTT IN 0V
              > > /PTT IN ~10.5V
              > > S12V 0V
              > >
              > > PTT IN was then connected to 12V (Cathode D1). Readings now:
              > >
              > > /PTT IN 0V
              > > S12V ~11.8V
              > >
              > > PTT IN back to 0V (connected to ground). Readings now:
              > >
              > > /PTT IN ~ 5.8V
              > > S12V ~11.8V
              > >
              > > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
              > > indefinately - irrespective of changes to PTT untill the power is
              > > removed. The readings above can then be reproduced.
              > >
              > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish
              > (the
              > > value given in the detailed contruction notes)?
              > >
              > > Any help much appreciated.
              > >
              > > 73, Dave
              > >
              >
              > You probably have it fixed by now but I have a partial
              > troubleshooting page on that section at
              >
              > http://golddredgervideo.com/kc0wox/softrock/tx/misc.htm
              >
              > I haven't finished it yet but it goes through much of the switching
              > part.
              > Leonard
              >
            • singhpk99
              Hi, Is your Q2 and 3906 (pnp) or is it a 3904 ? It could easily have been interchanged . 73s ab2xf
              Message 6 of 29 , Sep 24, 2008
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                Hi,

                Is your Q2 and 3906 (pnp) or is it a 3904 ?
                It could easily have been interchanged .
                73s
                ab2xf

                --- In softrock40@yahoogroups.com, "Leonard" <dredger@...> wrote:
                >
                > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                > >
                > > I'm having trouble with the simplest element of the RXTX6.3
                > > transmitter section and would appreciate some help before I start
                > > pulling out components.
                > >
                > > The RX seems to work fine. I've checked soldering and component
                > > values under magnification. I used good ESD practice throughout
                > > construction.
                > >
                > > The problem is with the PTT section. Construction of the main
                > board
                > > is complete and I'm testing without the PA daughter board
                > installed.
                > > My original problem was that when testing the PA module The
                > current
                > > draw exceeded my 150mA current limit, knocking the supply voltage
                > > down to a couple of volts. I decided to check the voltages at
                > J1 /
                > > J2 before faulting the PA board.
                > >
                > > On power up the current draw is ~95mA @ 7.047 center frequency.
                > With
                > > a DMM I measure:
                > >
                > > PTT IN 0V
                > > /PTT IN ~10.5V
                > > S12V 0V
                > >
                > > PTT IN was then connected to 12V (Cathode D1). Readings now:
                > >
                > > /PTT IN 0V
                > > S12V ~11.8V
                > >
                > > PTT IN back to 0V (connected to ground). Readings now:
                > >
                > > /PTT IN ~ 5.8V
                > > S12V ~11.8V
                > >
                > > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
                > > indefinately - irrespective of changes to PTT untill the power is
                > > removed. The readings above can then be reproduced.
                > >
                > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish
                > (the
                > > value given in the detailed contruction notes)?
                > >
                > > Any help much appreciated.
                > >
                > > 73, Dave
                > >
                >
                > You probably have it fixed by now but I have a partial
                > troubleshooting page on that section at
                >
                > http://golddredgervideo.com/kc0wox/softrock/tx/misc.htm
                >
                > I haven't finished it yet but it goes through much of the switching
                > part.
                > Leonard
                >
              • g8xul
                Thanks Mike, I still haven t resolved the issue. The collector of Q1 waggles up and down with PTT as expected (except that it is only 6V ish when PTT is low
                Message 7 of 29 , Sep 24, 2008
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                  Thanks Mike,

                  I still haven't resolved the issue. The collector of Q1 waggles up
                  and down with PTT as expected (except that it is only 6V ish when PTT
                  is low instead of the ~12 I would expect). I've double checked
                  soldering and component values. All the 'in circuit' resistance
                  measurements I've taken look reasonable.

                  I tried shunting R22 with a resistor from the 12V line and found a
                  value of ~500 ohm would make Q2 unlatch, but it latched again next
                  time PTT was taken high.

                  I've now pulled Q2 from the circuit and will test it tomorrow as well
                  as checking the circuit around it with it out of circuit.

                  I'll let you know how I get on. I think I'll lash up the same
                  circuit on the bench and see what happens! It feels a bit like
                  grasping at straws.

                  Regards,

                  Dave

                  --- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@...> wrote:
                  >
                  >
                  > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish
                  (the
                  > > value given in the detailed contruction notes)?
                  >
                  > Hi Dave,
                  >
                  > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an inversion.
                  >
                  > The only way for /PTT IN to be lower than 12-0.7V is for Q1 to be
                  > somewhat ON. For Q1 to be on: the Q1 BE must be above .6V or so. I
                  > would measure across R20 next time it latches up.
                  >
                  > R20 is used to drain the voltage on the C27 (at .7V when Q1 ON) down
                  > to help turn off Q1. With no PTTIN voltage the R20 voltage should
                  be
                  > at 0 V.
                  >
                  > Q1 turns on when the PTT IN start going above 1.2V or so. This
                  > happens when the R19/R20 divider starts to go higher than .6V; when
                  > the BE junction starts turning on. When fully on Q1 collector
                  should
                  > be at about .2 V or so.
                  >
                  > Q2 does about the opposite: when /PTTIN goes low; the BE junction of
                  > Q2 turns on (at about 12V-0.6V) and then S12V goes close to 12V
                  (i.e.
                  > 12V - 0.2V).
                  >
                  > 73, Mike Collins KF4BQ
                  >
                • g8xul
                  I ve checked all the transistor types - definately 3906. Fair comment though. Regards, Dave ... start ... component ... throughout ... voltage ... is ...
                  Message 8 of 29 , Sep 24, 2008
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                    I've checked all the transistor types - definately 3906. Fair
                    comment though.

                    Regards,

                    Dave

                    --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@...> wrote:
                    >
                    > Hi,
                    >
                    > Is your Q2 and 3906 (pnp) or is it a 3904 ?
                    > It could easily have been interchanged .
                    > 73s
                    > ab2xf
                    >
                    > --- In softrock40@yahoogroups.com, "Leonard" <dredger@> wrote:
                    > >
                    > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                    > > >
                    > > > I'm having trouble with the simplest element of the RXTX6.3
                    > > > transmitter section and would appreciate some help before I
                    start
                    > > > pulling out components.
                    > > >
                    > > > The RX seems to work fine. I've checked soldering and
                    component
                    > > > values under magnification. I used good ESD practice
                    throughout
                    > > > construction.
                    > > >
                    > > > The problem is with the PTT section. Construction of the main
                    > > board
                    > > > is complete and I'm testing without the PA daughter board
                    > > installed.
                    > > > My original problem was that when testing the PA module The
                    > > current
                    > > > draw exceeded my 150mA current limit, knocking the supply
                    voltage
                    > > > down to a couple of volts. I decided to check the voltages at
                    > > J1 /
                    > > > J2 before faulting the PA board.
                    > > >
                    > > > On power up the current draw is ~95mA @ 7.047 center frequency.
                    > > With
                    > > > a DMM I measure:
                    > > >
                    > > > PTT IN 0V
                    > > > /PTT IN ~10.5V
                    > > > S12V 0V
                    > > >
                    > > > PTT IN was then connected to 12V (Cathode D1). Readings now:
                    > > >
                    > > > /PTT IN 0V
                    > > > S12V ~11.8V
                    > > >
                    > > > PTT IN back to 0V (connected to ground). Readings now:
                    > > >
                    > > > /PTT IN ~ 5.8V
                    > > > S12V ~11.8V
                    > > >
                    > > > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
                    > > > indefinately - irrespective of changes to PTT untill the power
                    is
                    > > > removed. The readings above can then be reproduced.
                    > > >
                    > > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish
                    > > (the
                    > > > value given in the detailed contruction notes)?
                    > > >
                    > > > Any help much appreciated.
                    > > >
                    > > > 73, Dave
                    > > >
                    > >
                    > > You probably have it fixed by now but I have a partial
                    > > troubleshooting page on that section at
                    > >
                    > > http://golddredgervideo.com/kc0wox/softrock/tx/misc.htm
                    > >
                    > > I haven't finished it yet but it goes through much of the
                    switching
                    > > part.
                    > > Leonard
                    > >
                    >
                  • g8xul
                    I ve measured 12V rail to R21 hairping in circuit at ~7.5kOhm. Sounds reasonable. Good suggestion on the open cct PTH. If Q2 tests ok I ll try soldering the
                    Message 9 of 29 , Sep 24, 2008
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                      I've measured 12V rail to R21 hairping in circuit at ~7.5kOhm.
                      Sounds reasonable. Good suggestion on the open cct PTH. If Q2 tests
                      ok I'll try soldering the top side of all I can get at.

                      73, Dave


                      --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@...> wrote:
                      >
                      > Hi Dave,
                      >
                      > Is the value of R21 in yr 6.3 rxtx 49.9 ohm(gold band) instead of
                      > 4.9k? Your Q2 may be toast also . Please use a multimeter to check
                      > resistances and continuity with power off around Q2 and Q1 .
                      > Dont rule out a dry solder joint either- PTH vias can be open at
                      times
                      > also.
                      >
                      > I am just compelting my rxtx6.3 also - have to build the filter
                      > modules and the PA yet.
                      >
                      > 73s
                      > ab2xf
                      > --- In softrock40@yahoogroups.com, "Leonard" <dredger@> wrote:
                      > >
                      > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                      > > >
                      > > > I'm having trouble with the simplest element of the RXTX6.3
                      > > > transmitter section and would appreciate some help before I
                      start
                      > > > pulling out components.
                      > > >
                      > > > The RX seems to work fine. I've checked soldering and
                      component
                      > > > values under magnification. I used good ESD practice
                      throughout
                      > > > construction.
                      > > >
                      > > > The problem is with the PTT section. Construction of the main
                      > > board
                      > > > is complete and I'm testing without the PA daughter board
                      > > installed.
                      > > > My original problem was that when testing the PA module The
                      > > current
                      > > > draw exceeded my 150mA current limit, knocking the supply
                      voltage
                      > > > down to a couple of volts. I decided to check the voltages at
                      > > J1 /
                      > > > J2 before faulting the PA board.
                      > > >
                      > > > On power up the current draw is ~95mA @ 7.047 center frequency.
                      > > With
                      > > > a DMM I measure:
                      > > >
                      > > > PTT IN 0V
                      > > > /PTT IN ~10.5V
                      > > > S12V 0V
                      > > >
                      > > > PTT IN was then connected to 12V (Cathode D1). Readings now:
                      > > >
                      > > > /PTT IN 0V
                      > > > S12V ~11.8V
                      > > >
                      > > > PTT IN back to 0V (connected to ground). Readings now:
                      > > >
                      > > > /PTT IN ~ 5.8V
                      > > > S12V ~11.8V
                      > > >
                      > > > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
                      > > > indefinately - irrespective of changes to PTT untill the power
                      is
                      > > > removed. The readings above can then be reproduced.
                      > > >
                      > > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish
                      > > (the
                      > > > value given in the detailed contruction notes)?
                      > > >
                      > > > Any help much appreciated.
                      > > >
                      > > > 73, Dave
                      > > >
                      > >
                      > > You probably have it fixed by now but I have a partial
                      > > troubleshooting page on that section at
                      > >
                      > > http://golddredgervideo.com/kc0wox/softrock/tx/misc.htm
                      > >
                      > > I haven't finished it yet but it goes through much of the
                      switching
                      > > part.
                      > > Leonard
                      > >
                      >
                    • g8xul
                      Thanks anyway Leonard. I m a bit rusty at my faulting. Too many years doing 1s and 0s and project plans :-) Dave ... switching
                      Message 10 of 29 , Sep 24, 2008
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                        Thanks anyway Leonard. I'm a bit rusty at my faulting. Too many
                        years doing 1s and 0s and project plans :-)

                        Dave

                        --- In softrock40@yahoogroups.com, "Leonard" <dredger@...> wrote:
                        >
                        > --- In softrock40@yahoogroups.com, "Leonard" <dredger@> wrote:
                        > >
                        > > You probably have it fixed by now but I have a partial
                        > > troubleshooting page on that section at
                        > >
                        > > http://golddredgervideo.com/kc0wox/softrock/tx/misc.htm
                        > >
                        > > I haven't finished it yet but it goes through much of the
                        switching
                        > > part.
                        > > Leonard
                        > >
                        >
                        >
                        > Opps!
                        >
                        > My page is for a 6.2, not a 6.3. Too many versions out.
                        > Leonard
                        >
                      • g8xul
                        Q2 tests fine. BC and BE junctions look good, 0.65ish volts forward and high impedance reverse biased. Using the same values as the board for R21 and R22 the
                        Message 11 of 29 , Sep 25, 2008
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                          Q2 tests fine. BC and BE junctions look good, 0.65ish volts forward
                          and high impedance reverse biased. Using the same values as the
                          board for R21 and R22 the stage works as expected in isolation. Q1
                          inverter also swings 0v to 12v with ptt. Again, all resistance
                          measurements taken with Q2 out of circuit look right.

                          Resoldering Q2 into the board the latching problem is still there.
                          Next move is to isolate Q1/2 stages by lifting R24 and R29.

                          Any more ideas? Sorry to be a pain but this is driving me mad!

                          73,
                          Dave

                          --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
                          >
                          > Thanks Mike,
                          >
                          > I still haven't resolved the issue. The collector of Q1 waggles up
                          > and down with PTT as expected (except that it is only 6V ish when
                          PTT
                          > is low instead of the ~12 I would expect). I've double checked
                          > soldering and component values. All the 'in circuit' resistance
                          > measurements I've taken look reasonable.
                          >
                          > I tried shunting R22 with a resistor from the 12V line and found a
                          > value of ~500 ohm would make Q2 unlatch, but it latched again next
                          > time PTT was taken high.
                          >
                          > I've now pulled Q2 from the circuit and will test it tomorrow as
                          well
                          > as checking the circuit around it with it out of circuit.
                          >
                          > I'll let you know how I get on. I think I'll lash up the same
                          > circuit on the bench and see what happens! It feels a bit like
                          > grasping at straws.
                          >
                          > Regards,
                          >
                          > Dave
                          >
                          > --- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@> wrote:
                          > >
                          > >
                          > > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish
                          > (the
                          > > > value given in the detailed contruction notes)?
                          > >
                          > > Hi Dave,
                          > >
                          > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an
                          inversion.
                          > >
                          > > The only way for /PTT IN to be lower than 12-0.7V is for Q1 to be
                          > > somewhat ON. For Q1 to be on: the Q1 BE must be above .6V or
                          so. I
                          > > would measure across R20 next time it latches up.
                          > >
                          > > R20 is used to drain the voltage on the C27 (at .7V when Q1 ON)
                          down
                          > > to help turn off Q1. With no PTTIN voltage the R20 voltage
                          should
                          > be
                          > > at 0 V.
                          > >
                          > > Q1 turns on when the PTT IN start going above 1.2V or so. This
                          > > happens when the R19/R20 divider starts to go higher than .6V;
                          when
                          > > the BE junction starts turning on. When fully on Q1 collector
                          > should
                          > > be at about .2 V or so.
                          > >
                          > > Q2 does about the opposite: when /PTTIN goes low; the BE junction
                          of
                          > > Q2 turns on (at about 12V-0.6V) and then S12V goes close to 12V
                          > (i.e.
                          > > 12V - 0.2V).
                          > >
                          > > 73, Mike Collins KF4BQ
                          > >
                          >
                        • Mike Collins
                          ... Hi Dave, The only other thing on /PTT IN chain is the RX Ant Sw Q7. Check the gate on Q7 via R30. If Q7 was shorted somehow, then R30 would pull down the
                          Message 12 of 29 , Sep 25, 2008
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                            > Any more ideas? Sorry to be a pain but this is driving me mad!
                            >
                            Hi Dave,

                            The only other thing on /PTT IN chain is the RX Ant Sw Q7. Check the
                            gate on Q7 via R30. If Q7 was shorted somehow, then R30 would pull
                            down the /PTT IN buss.

                            It has to be the collector of Q1 or the gate of Q7 pulling the line
                            down somehow.

                            73, Mike Collins KF4BQ
                          • g8xul
                            Thanks for the support Mike, I agree. Removing R29 will isolate the rx switch and R24 the ptto section. The s12V line into the rx switch reads several megs
                            Message 13 of 29 , Sep 25, 2008
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                              Thanks for the support Mike,

                              I agree. Removing R29 will isolate the rx switch and R24 the ptto
                              section. The s12V line into the rx switch reads several megs to earth
                              on the meter with Q2 out of the board but.... I'll let you know how
                              that goes!

                              73,
                              Dave
                              --- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@...> wrote:
                              >
                              > > Any more ideas? Sorry to be a pain but this is driving me mad!
                              > >
                              > Hi Dave,
                              >
                              > The only other thing on /PTT IN chain is the RX Ant Sw Q7. Check the
                              > gate on Q7 via R30. If Q7 was shorted somehow, then R30 would pull
                              > down the /PTT IN buss.
                              >
                              > It has to be the collector of Q1 or the gate of Q7 pulling the line
                              > down somehow.
                              >
                              > 73, Mike Collins KF4BQ
                              >
                            • singhpk99
                              It could be oscillating ! Do you have scope? Please check the Q1, Q2 base and collectors using a scope. 73s Push AB2xf ... forward ... up ... a ... next ...
                              Message 14 of 29 , Sep 26, 2008
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                                It could be oscillating !

                                Do you have scope?

                                Please check the Q1, Q2 base and collectors using a scope.

                                73s
                                Push
                                AB2xf


                                --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
                                >
                                > Q2 tests fine. BC and BE junctions look good, 0.65ish volts
                                forward
                                > and high impedance reverse biased. Using the same values as the
                                > board for R21 and R22 the stage works as expected in isolation. Q1
                                > inverter also swings 0v to 12v with ptt. Again, all resistance
                                > measurements taken with Q2 out of circuit look right.
                                >
                                > Resoldering Q2 into the board the latching problem is still there.
                                > Next move is to isolate Q1/2 stages by lifting R24 and R29.
                                >
                                > Any more ideas? Sorry to be a pain but this is driving me mad!
                                >
                                > 73,
                                > Dave
                                >
                                > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                > >
                                > > Thanks Mike,
                                > >
                                > > I still haven't resolved the issue. The collector of Q1 waggles
                                up
                                > > and down with PTT as expected (except that it is only 6V ish when
                                > PTT
                                > > is low instead of the ~12 I would expect). I've double checked
                                > > soldering and component values. All the 'in circuit' resistance
                                > > measurements I've taken look reasonable.
                                > >
                                > > I tried shunting R22 with a resistor from the 12V line and found
                                a
                                > > value of ~500 ohm would make Q2 unlatch, but it latched again
                                next
                                > > time PTT was taken high.
                                > >
                                > > I've now pulled Q2 from the circuit and will test it tomorrow as
                                > well
                                > > as checking the circuit around it with it out of circuit.
                                > >
                                > > I'll let you know how I get on. I think I'll lash up the same
                                > > circuit on the bench and see what happens! It feels a bit like
                                > > grasping at straws.
                                > >
                                > > Regards,
                                > >
                                > > Dave
                                > >
                                > > --- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@>
                                wrote:
                                > > >
                                > > >
                                > > > > Should S12V not follow PTT? Why does /PTT IN reduce to
                                5V'ish
                                > > (the
                                > > > > value given in the detailed contruction notes)?
                                > > >
                                > > > Hi Dave,
                                > > >
                                > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an
                                > inversion.
                                > > >
                                > > > The only way for /PTT IN to be lower than 12-0.7V is for Q1 to
                                be
                                > > > somewhat ON. For Q1 to be on: the Q1 BE must be above .6V or
                                > so. I
                                > > > would measure across R20 next time it latches up.
                                > > >
                                > > > R20 is used to drain the voltage on the C27 (at .7V when Q1 ON)
                                > down
                                > > > to help turn off Q1. With no PTTIN voltage the R20 voltage
                                > should
                                > > be
                                > > > at 0 V.
                                > > >
                                > > > Q1 turns on when the PTT IN start going above 1.2V or so. This
                                > > > happens when the R19/R20 divider starts to go higher than .6V;
                                > when
                                > > > the BE junction starts turning on. When fully on Q1 collector
                                > > should
                                > > > be at about .2 V or so.
                                > > >
                                > > > Q2 does about the opposite: when /PTTIN goes low; the BE
                                junction
                                > of
                                > > > Q2 turns on (at about 12V-0.6V) and then S12V goes close to 12V
                                > > (i.e.
                                > > > 12V - 0.2V).
                                > > >
                                > > > 73, Mike Collins KF4BQ
                                > > >
                                > >
                                >
                              • Tim O'Rourke
                                Be sure that the wiring to serial port is spot on, so simple it may have not been obvious. Do not ask how I know this can affect keying! Tim W4YN
                                Message 15 of 29 , Sep 26, 2008
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                                  Be sure that the wiring to serial port is spot on, so simple it may
                                  have not been obvious. Do not ask how I know this can affect keying!
                                  Tim W4YN

                                  --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@...> wrote:
                                  >
                                  >
                                  > It could be oscillating !
                                  >
                                  > Do you have scope?
                                  >
                                  > Please check the Q1, Q2 base and collectors using a scope.
                                  >
                                  > 73s
                                  > Push
                                  > AB2xf
                                  >
                                  >
                                  > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                  > >
                                  > > Q2 tests fine. BC and BE junctions look good, 0.65ish volts
                                  > forward
                                  > > and high impedance reverse biased. Using the same values as the
                                  > > board for R21 and R22 the stage works as expected in isolation. Q1
                                  > > inverter also swings 0v to 12v with ptt. Again, all resistance
                                  > > measurements taken with Q2 out of circuit look right.
                                  > >
                                  > > Resoldering Q2 into the board the latching problem is still there.
                                  > > Next move is to isolate Q1/2 stages by lifting R24 and R29.
                                  > >
                                  > > Any more ideas? Sorry to be a pain but this is driving me mad!
                                  > >
                                  > > 73,
                                  > > Dave
                                  > >
                                  > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                  > > >
                                  > > > Thanks Mike,
                                  > > >
                                  > > > I still haven't resolved the issue. The collector of Q1 waggles
                                  > up
                                  > > > and down with PTT as expected (except that it is only 6V ish when
                                  > > PTT
                                  > > > is low instead of the ~12 I would expect). I've double checked
                                  > > > soldering and component values. All the 'in circuit' resistance
                                  > > > measurements I've taken look reasonable.
                                  > > >
                                  > > > I tried shunting R22 with a resistor from the 12V line and found
                                  > a
                                  > > > value of ~500 ohm would make Q2 unlatch, but it latched again
                                  > next
                                  > > > time PTT was taken high.
                                  > > >
                                  > > > I've now pulled Q2 from the circuit and will test it tomorrow as
                                  > > well
                                  > > > as checking the circuit around it with it out of circuit.
                                  > > >
                                  > > > I'll let you know how I get on. I think I'll lash up the same
                                  > > > circuit on the bench and see what happens! It feels a bit like
                                  > > > grasping at straws.
                                  > > >
                                  > > > Regards,
                                  > > >
                                  > > > Dave
                                  > > >
                                  > > > --- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@>
                                  > wrote:
                                  > > > >
                                  > > > >
                                  > > > > > Should S12V not follow PTT? Why does /PTT IN reduce to
                                  > 5V'ish
                                  > > > (the
                                  > > > > > value given in the detailed contruction notes)?
                                  > > > >
                                  > > > > Hi Dave,
                                  > > > >
                                  > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an
                                  > > inversion.
                                  > > > >
                                  > > > > The only way for /PTT IN to be lower than 12-0.7V is for Q1 to
                                  > be
                                  > > > > somewhat ON. For Q1 to be on: the Q1 BE must be above .6V or
                                  > > so. I
                                  > > > > would measure across R20 next time it latches up.
                                  > > > >
                                  > > > > R20 is used to drain the voltage on the C27 (at .7V when Q1 ON)
                                  > > down
                                  > > > > to help turn off Q1. With no PTTIN voltage the R20 voltage
                                  > > should
                                  > > > be
                                  > > > > at 0 V.
                                  > > > >
                                  > > > > Q1 turns on when the PTT IN start going above 1.2V or so. This
                                  > > > > happens when the R19/R20 divider starts to go higher than .6V;
                                  > > when
                                  > > > > the BE junction starts turning on. When fully on Q1 collector
                                  > > > should
                                  > > > > be at about .2 V or so.
                                  > > > >
                                  > > > > Q2 does about the opposite: when /PTTIN goes low; the BE
                                  > junction
                                  > > of
                                  > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes close to 12V
                                  > > > (i.e.
                                  > > > > 12V - 0.2V).
                                  > > > >
                                  > > > > 73, Mike Collins KF4BQ
                                  > > > >
                                  > > >
                                  > >
                                  >
                                • singhpk99
                                  Please try bypassing C47 and C27 with .1uf and try again If you have it happeing in your rxtx, it may be happening in mine as well- will check 73s ab2xf
                                  Message 16 of 29 , Sep 27, 2008
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                                    Please try bypassing C47 and C27 with .1uf and try again
                                    If you have it happeing in your rxtx, it may be happening in mine as
                                    well- will check

                                    73s

                                    ab2xf




                                    --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@...> wrote:
                                    >
                                    > Be sure that the wiring to serial port is spot on, so simple it may
                                    > have not been obvious. Do not ask how I know this can affect keying!
                                    > Tim W4YN
                                    >
                                    > --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@> wrote:
                                    > >
                                    > >
                                    > > It could be oscillating !
                                    > >
                                    > > Do you have scope?
                                    > >
                                    > > Please check the Q1, Q2 base and collectors using a scope.
                                    > >
                                    > > 73s
                                    > > Push
                                    > > AB2xf
                                    > >
                                    > >
                                    > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                    > > >
                                    > > > Q2 tests fine. BC and BE junctions look good, 0.65ish volts
                                    > > forward
                                    > > > and high impedance reverse biased. Using the same values as the
                                    > > > board for R21 and R22 the stage works as expected in isolation. Q1
                                    > > > inverter also swings 0v to 12v with ptt. Again, all resistance
                                    > > > measurements taken with Q2 out of circuit look right.
                                    > > >
                                    > > > Resoldering Q2 into the board the latching problem is still there.
                                    > > > Next move is to isolate Q1/2 stages by lifting R24 and R29.
                                    > > >
                                    > > > Any more ideas? Sorry to be a pain but this is driving me mad!
                                    > > >
                                    > > > 73,
                                    > > > Dave
                                    > > >
                                    > > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                    > > > >
                                    > > > > Thanks Mike,
                                    > > > >
                                    > > > > I still haven't resolved the issue. The collector of Q1 waggles
                                    > > up
                                    > > > > and down with PTT as expected (except that it is only 6V ish when
                                    > > > PTT
                                    > > > > is low instead of the ~12 I would expect). I've double checked
                                    > > > > soldering and component values. All the 'in circuit' resistance
                                    > > > > measurements I've taken look reasonable.
                                    > > > >
                                    > > > > I tried shunting R22 with a resistor from the 12V line and found
                                    > > a
                                    > > > > value of ~500 ohm would make Q2 unlatch, but it latched again
                                    > > next
                                    > > > > time PTT was taken high.
                                    > > > >
                                    > > > > I've now pulled Q2 from the circuit and will test it tomorrow as
                                    > > > well
                                    > > > > as checking the circuit around it with it out of circuit.
                                    > > > >
                                    > > > > I'll let you know how I get on. I think I'll lash up the same
                                    > > > > circuit on the bench and see what happens! It feels a bit like
                                    > > > > grasping at straws.
                                    > > > >
                                    > > > > Regards,
                                    > > > >
                                    > > > > Dave
                                    > > > >
                                    > > > > --- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@>
                                    > > wrote:
                                    > > > > >
                                    > > > > >
                                    > > > > > > Should S12V not follow PTT? Why does /PTT IN reduce to
                                    > > 5V'ish
                                    > > > > (the
                                    > > > > > > value given in the detailed contruction notes)?
                                    > > > > >
                                    > > > > > Hi Dave,
                                    > > > > >
                                    > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an
                                    > > > inversion.
                                    > > > > >
                                    > > > > > The only way for /PTT IN to be lower than 12-0.7V is for Q1 to
                                    > > be
                                    > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be above .6V or
                                    > > > so. I
                                    > > > > > would measure across R20 next time it latches up.
                                    > > > > >
                                    > > > > > R20 is used to drain the voltage on the C27 (at .7V when Q1 ON)
                                    > > > down
                                    > > > > > to help turn off Q1. With no PTTIN voltage the R20 voltage
                                    > > > should
                                    > > > > be
                                    > > > > > at 0 V.
                                    > > > > >
                                    > > > > > Q1 turns on when the PTT IN start going above 1.2V or so. This
                                    > > > > > happens when the R19/R20 divider starts to go higher than .6V;
                                    > > > when
                                    > > > > > the BE junction starts turning on. When fully on Q1 collector
                                    > > > > should
                                    > > > > > be at about .2 V or so.
                                    > > > > >
                                    > > > > > Q2 does about the opposite: when /PTTIN goes low; the BE
                                    > > junction
                                    > > > of
                                    > > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes close to 12V
                                    > > > > (i.e.
                                    > > > > > 12V - 0.2V).
                                    > > > > >
                                    > > > > > 73, Mike Collins KF4BQ
                                    > > > > >
                                    > > > >
                                    > > >
                                    > >
                                    >
                                  • g8xul
                                    Thanks everyone for their helpful comments. Made some progress yesterday. I removed R29 and R30 to isolate the PTT stage. The S12V line then switched
                                    Message 17 of 29 , Sep 27, 2008
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                                      Thanks everyone for their helpful comments.

                                      Made some progress yesterday. I removed R29 and R30 to isolate the
                                      PTT stage. The S12V line then switched correctly - no latching.
                                      The /ptt line also swings 0 to 12V.

                                      I removed Q7 and Q8 and found Q7 to be duff. About 600ohms between
                                      each terminal. Q8 seems ok although my testing is a bit basic. S to
                                      D is high resistance until a finger is used to bias the gate when it
                                      falls to a few ohms. Plunging the leads into anti static foam resets
                                      it to high impedance.

                                      Resistances around the connections to Q7/8 on the board looked ok.

                                      I replaced Q7 with a new device and powered up the board. The
                                      latching problem returned and the new Q7 has lost its magic smoke.
                                      Same 600ohms between terminals.

                                      I'm going to build the stage in multisim and see if I can try out
                                      some faults on that.

                                      Back to the debug on Monday. Glad I've got the support of a great
                                      group.

                                      73,

                                      Dave



                                      --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@...> wrote:
                                      >
                                      >
                                      > Please try bypassing C47 and C27 with .1uf and try again
                                      > If you have it happeing in your rxtx, it may be happening in mine as
                                      > well- will check
                                      >
                                      > 73s
                                      >
                                      > ab2xf
                                      >
                                      >
                                      >
                                      >
                                      > --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@> wrote:
                                      > >
                                      > > Be sure that the wiring to serial port is spot on, so simple it
                                      may
                                      > > have not been obvious. Do not ask how I know this can affect
                                      keying!
                                      > > Tim W4YN
                                      > >
                                      > > --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@> wrote:
                                      > > >
                                      > > >
                                      > > > It could be oscillating !
                                      > > >
                                      > > > Do you have scope?
                                      > > >
                                      > > > Please check the Q1, Q2 base and collectors using a scope.
                                      > > >
                                      > > > 73s
                                      > > > Push
                                      > > > AB2xf
                                      > > >
                                      > > >
                                      > > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                      > > > >
                                      > > > > Q2 tests fine. BC and BE junctions look good, 0.65ish volts
                                      > > > forward
                                      > > > > and high impedance reverse biased. Using the same values as
                                      the
                                      > > > > board for R21 and R22 the stage works as expected in
                                      isolation. Q1
                                      > > > > inverter also swings 0v to 12v with ptt. Again, all
                                      resistance
                                      > > > > measurements taken with Q2 out of circuit look right.
                                      > > > >
                                      > > > > Resoldering Q2 into the board the latching problem is still
                                      there.
                                      > > > > Next move is to isolate Q1/2 stages by lifting R24 and R29.
                                      > > > >
                                      > > > > Any more ideas? Sorry to be a pain but this is driving me
                                      mad!
                                      > > > >
                                      > > > > 73,
                                      > > > > Dave
                                      > > > >
                                      > > > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@>
                                      wrote:
                                      > > > > >
                                      > > > > > Thanks Mike,
                                      > > > > >
                                      > > > > > I still haven't resolved the issue. The collector of Q1
                                      waggles
                                      > > > up
                                      > > > > > and down with PTT as expected (except that it is only 6V
                                      ish when
                                      > > > > PTT
                                      > > > > > is low instead of the ~12 I would expect). I've double
                                      checked
                                      > > > > > soldering and component values. All the 'in circuit'
                                      resistance
                                      > > > > > measurements I've taken look reasonable.
                                      > > > > >
                                      > > > > > I tried shunting R22 with a resistor from the 12V line and
                                      found
                                      > > > a
                                      > > > > > value of ~500 ohm would make Q2 unlatch, but it latched
                                      again
                                      > > > next
                                      > > > > > time PTT was taken high.
                                      > > > > >
                                      > > > > > I've now pulled Q2 from the circuit and will test it
                                      tomorrow as
                                      > > > > well
                                      > > > > > as checking the circuit around it with it out of circuit.
                                      > > > > >
                                      > > > > > I'll let you know how I get on. I think I'll lash up the
                                      same
                                      > > > > > circuit on the bench and see what happens! It feels a bit
                                      like
                                      > > > > > grasping at straws.
                                      > > > > >
                                      > > > > > Regards,
                                      > > > > >
                                      > > > > > Dave
                                      > > > > >
                                      > > > > > --- In softrock40@yahoogroups.com, "Mike Collins"
                                      <mikecol@>
                                      > > > wrote:
                                      > > > > > >
                                      > > > > > >
                                      > > > > > > > Should S12V not follow PTT? Why does /PTT IN reduce to
                                      > > > 5V'ish
                                      > > > > > (the
                                      > > > > > > > value given in the detailed contruction notes)?
                                      > > > > > >
                                      > > > > > > Hi Dave,
                                      > > > > > >
                                      > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an
                                      > > > > inversion.
                                      > > > > > >
                                      > > > > > > The only way for /PTT IN to be lower than 12-0.7V is for
                                      Q1 to
                                      > > > be
                                      > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be
                                      above .6V or
                                      > > > > so. I
                                      > > > > > > would measure across R20 next time it latches up.
                                      > > > > > >
                                      > > > > > > R20 is used to drain the voltage on the C27 (at .7V when
                                      Q1 ON)
                                      > > > > down
                                      > > > > > > to help turn off Q1. With no PTTIN voltage the R20
                                      voltage
                                      > > > > should
                                      > > > > > be
                                      > > > > > > at 0 V.
                                      > > > > > >
                                      > > > > > > Q1 turns on when the PTT IN start going above 1.2V or
                                      so. This
                                      > > > > > > happens when the R19/R20 divider starts to go higher
                                      than .6V;
                                      > > > > when
                                      > > > > > > the BE junction starts turning on. When fully on Q1
                                      collector
                                      > > > > > should
                                      > > > > > > be at about .2 V or so.
                                      > > > > > >
                                      > > > > > > Q2 does about the opposite: when /PTTIN goes low; the BE
                                      > > > junction
                                      > > > > of
                                      > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes close
                                      to 12V
                                      > > > > > (i.e.
                                      > > > > > > 12V - 0.2V).
                                      > > > > > >
                                      > > > > > > 73, Mike Collins KF4BQ
                                      > > > > > >
                                      > > > > >
                                      > > > >
                                      > > >
                                      > >
                                      >
                                    • Tony Parks
                                      Hi Dave, Please check to make sure C30 is not shorted and that D2 is mounted with the band end of the diode connected to the base of Q1. 73, Tony KB9YIG ...
                                      Message 18 of 29 , Sep 27, 2008
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                                        Hi Dave,
                                         
                                        Please check to make sure C30 is not shorted and that D2 is mounted with the band end of the diode connected to the base of Q1.
                                         
                                        73,
                                        Tony KB9YIG
                                         
                                        ----- Original Message -----
                                        From: g8xul
                                        Sent: Saturday, September 27, 2008 4:32 PM
                                        Subject: [softrock40] Re: Troubleshooting RXTX 6.3

                                        Thanks everyone for their helpful comments.

                                        Made some progress yesterday. I removed R29 and R30 to isolate the
                                        PTT stage. The S12V line then switched correctly - no latching.
                                        The /ptt line also swings 0 to 12V.

                                        I removed Q7 and Q8 and found Q7 to be duff. About 600ohms between
                                        each terminal. Q8 seems ok although my testing is a bit basic. S to
                                        D is high resistance until a finger is used to bias the gate when it
                                        falls to a few ohms. Plunging the leads into anti static foam resets
                                        it to high impedance.

                                        Resistances around the connections to Q7/8 on the board looked ok.

                                        I replaced Q7 with a new device and powered up the board. The
                                        latching problem returned and the new Q7 has lost its magic smoke.
                                        Same 600ohms between terminals.

                                        I'm going to build the stage in multisim and see if I can try out
                                        some faults on that.

                                        Back to the debug on Monday. Glad I've got the support of a great
                                        group.

                                        73,

                                        Dave

                                        --- In softrock40@yahoogro ups.com, "singhpk99" <singhpk99@. ..> wrote:
                                        >
                                        >
                                        > Please try bypassing C47 and C27 with .1uf and try again
                                        > If you have it happeing in your rxtx, it may be happening in mine as
                                        > well- will check
                                        >
                                        > 73s
                                        >
                                        > ab2xf
                                        >
                                        >
                                        >
                                        >
                                        > --- In softrock40@yahoogro ups.com, "Tim O'Rourke" <w4yn@> wrote:
                                        > >
                                        > > Be sure that the wiring to serial port is spot on, so simple it
                                        may
                                        > > have not been obvious. Do not ask how I know this can affect
                                        keying!
                                        > > Tim W4YN
                                        > >
                                        > > --- In softrock40@yahoogro ups.com, "singhpk99" <singhpk99@> wrote:
                                        > > >
                                        > > >
                                        > > > It could be oscillating !
                                        > > >
                                        > > > Do you have scope?
                                        > > >
                                        > > > Please check the Q1, Q2 base and collectors using a scope.
                                        > > >
                                        > > > 73s
                                        > > > Push
                                        > > > AB2xf
                                        > > >
                                        > > >
                                        > > > --- In softrock40@yahoogro ups.com, "g8xul" <dave.james@ > wrote:
                                        > > > >
                                        > > > > Q2 tests fine. BC and BE junctions look good, 0.65ish volts
                                        > > > forward
                                        > > > > and high impedance reverse biased. Using the same values as
                                        the
                                        > > > > board for R21 and R22 the stage works as expected in
                                        isolation. Q1
                                        > > > > inverter also swings 0v to 12v with ptt. Again, all
                                        resistance
                                        > > > > measurements taken with Q2 out of circuit look right.
                                        > > > >
                                        > > > > Resoldering Q2 into the board the latching problem is still
                                        there.
                                        > > > > Next move is to isolate Q1/2 stages by lifting R24 and R29.
                                        > > > >
                                        > > > > Any more ideas? Sorry to be a pain but this is driving me
                                        mad!
                                        > > > >
                                        > > > > 73,
                                        > > > > Dave
                                        > > > >
                                        > > > > --- In softrock40@yahoogro ups.com, "g8xul" <dave.james@ >
                                        wrote:
                                        > > > > >
                                        > > > > > Thanks Mike,
                                        > > > > >
                                        > > > > > I still haven't resolved the issue. The collector of Q1
                                        waggles
                                        > > > up
                                        > > > > > and down with PTT as expected (except that it is only 6V
                                        ish when
                                        > > > > PTT
                                        > > > > > is low instead of the ~12 I would expect). I've double
                                        checked
                                        > > > > > soldering and component values. All the 'in circuit'
                                        resistance
                                        > > > > > measurements I've taken look reasonable.
                                        > > > > >
                                        > > > > > I tried shunting R22 with a resistor from the 12V line and
                                        found
                                        > > > a
                                        > > > > > value of ~500 ohm would make Q2 unlatch, but it latched
                                        again
                                        > > > next
                                        > > > > > time PTT was taken high.
                                        > > > > >
                                        > > > > > I've now pulled Q2 from the circuit and will test it
                                        tomorrow as
                                        > > > > well
                                        > > > > > as checking the circuit around it with it out of circuit.
                                        > > > > >
                                        > > > > > I'll let you know how I get on. I think I'll lash up the
                                        same
                                        > > > > > circuit on the bench and see what happens! It feels a bit
                                        like
                                        > > > > > grasping at straws.
                                        > > > > >
                                        > > > > > Regards,
                                        > > > > >
                                        > > > > > Dave
                                        > > > > >
                                        > > > > > --- In softrock40@yahoogro ups.com, "Mike Collins"
                                        <mikecol@>
                                        > > > wrote:
                                        > > > > > >
                                        > > > > > >
                                        > > > > > > > Should S12V not follow PTT? Why does /PTT IN reduce to
                                        > > > 5V'ish
                                        > > > > > (the
                                        > > > > > > > value given in the detailed contruction notes)?
                                        > > > > > >
                                        > > > > > > Hi Dave,
                                        > > > > > >
                                        > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an
                                        > > > > inversion.
                                        > > > > > >
                                        > > > > > > The only way for /PTT IN to be lower than 12-0.7V is for
                                        Q1 to
                                        > > > be
                                        > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be
                                        above .6V or
                                        > > > > so. I
                                        > > > > > > would measure across R20 next time it latches up.
                                        > > > > > >
                                        > > > > > > R20 is used to drain the voltage on the C27 (at .7V when
                                        Q1 ON)
                                        > > > > down
                                        > > > > > > to help turn off Q1. With no PTTIN voltage the R20
                                        voltage
                                        > > > > should
                                        > > > > > be
                                        > > > > > > at 0 V.
                                        > > > > > >
                                        > > > > > > Q1 turns on when the PTT IN start going above 1.2V or
                                        so. This
                                        > > > > > > happens when the R19/R20 divider starts to go higher
                                        than .6V;
                                        > > > > when
                                        > > > > > > the BE junction starts turning on. When fully on Q1
                                        collector
                                        > > > > > should
                                        > > > > > > be at about .2 V or so.
                                        > > > > > >
                                        > > > > > > Q2 does about the opposite: when /PTTIN goes low; the BE
                                        > > > junction
                                        > > > > of
                                        > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes close
                                        to 12V
                                        > > > > > (i.e.
                                        > > > > > > 12V - 0.2V).
                                        > > > > > >
                                        > > > > > > 73, Mike Collins KF4BQ
                                        > > > > > >
                                        > > > > >
                                        > > > >
                                        > > >
                                        > >
                                        >

                                      • g8xul
                                        Thanks for reply Tony, I haven t got the board with me but: Please check to make sure C30 is not shorted I ll check tomorrow but I haven t got the PA
                                        Message 19 of 29 , Sep 28, 2008
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                                          Thanks for reply Tony,

                                          I haven't got the board with me but:

                                          "Please check to make sure C30 is not shorted"
                                          I'll check tomorrow but I haven't got the PA daughter board installed
                                          so C30 only goes to the J2 pin 5 (open circuit).

                                          "D2 is mounted with the band end of the diode connected to the base
                                          of Q1."

                                          I've checked this (but will check again) however the collector of Q1
                                          swings 0 to 12 V with the RX switches removed. I'm a bit confused by
                                          the test in the detailed build notes...

                                          "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                          Measure the voltage at R21 hairpin (/PTT-I). This should be ~5 Vdc.."

                                          On my board (with RX switches removed) this voltage is ~12V. When
                                          I've simulated the circuit (in Multisim) it also swings 0 to 12V.

                                          73, Dave

                                          --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@...> wrote:
                                          >
                                          > Hi Dave,
                                          >
                                          > Please check to make sure C30 is not shorted and that D2 is mounted
                                          with the band end of the diode connected to the base of Q1.
                                          >
                                          > 73,
                                          > Tony KB9YIG
                                          >
                                          > ----- Original Message -----
                                          > From: g8xul
                                          > To: softrock40@yahoogroups.com
                                          > Sent: Saturday, September 27, 2008 4:32 PM
                                          > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                          >
                                          >
                                          > Thanks everyone for their helpful comments.
                                          >
                                          > Made some progress yesterday. I removed R29 and R30 to isolate
                                          the
                                          > PTT stage. The S12V line then switched correctly - no latching.
                                          > The /ptt line also swings 0 to 12V.
                                          >
                                          > I removed Q7 and Q8 and found Q7 to be duff. About 600ohms
                                          between
                                          > each terminal. Q8 seems ok although my testing is a bit basic. S
                                          to
                                          > D is high resistance until a finger is used to bias the gate when
                                          it
                                          > falls to a few ohms. Plunging the leads into anti static foam
                                          resets
                                          > it to high impedance.
                                          >
                                          > Resistances around the connections to Q7/8 on the board looked ok.
                                          >
                                          > I replaced Q7 with a new device and powered up the board. The
                                          > latching problem returned and the new Q7 has lost its magic
                                          smoke.
                                          > Same 600ohms between terminals.
                                          >
                                          > I'm going to build the stage in multisim and see if I can try out
                                          > some faults on that.
                                          >
                                          > Back to the debug on Monday. Glad I've got the support of a great
                                          > group.
                                          >
                                          > 73,
                                          >
                                          > Dave
                                          >
                                          > --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@> wrote:
                                          > >
                                          > >
                                          > > Please try bypassing C47 and C27 with .1uf and try again
                                          > > If you have it happeing in your rxtx, it may be happening in
                                          mine as
                                          > > well- will check
                                          > >
                                          > > 73s
                                          > >
                                          > > ab2xf
                                          > >
                                          > >
                                          > >
                                          > >
                                          > > --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@> wrote:
                                          > > >
                                          > > > Be sure that the wiring to serial port is spot on, so simple
                                          it
                                          > may
                                          > > > have not been obvious. Do not ask how I know this can affect
                                          > keying!
                                          > > > Tim W4YN
                                          > > >
                                          > > > --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@>
                                          wrote:
                                          > > > >
                                          > > > >
                                          > > > > It could be oscillating !
                                          > > > >
                                          > > > > Do you have scope?
                                          > > > >
                                          > > > > Please check the Q1, Q2 base and collectors using a scope.
                                          > > > >
                                          > > > > 73s
                                          > > > > Push
                                          > > > > AB2xf
                                          > > > >
                                          > > > >
                                          > > > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@>
                                          wrote:
                                          > > > > >
                                          > > > > > Q2 tests fine. BC and BE junctions look good, 0.65ish
                                          volts
                                          > > > > forward
                                          > > > > > and high impedance reverse biased. Using the same values
                                          as
                                          > the
                                          > > > > > board for R21 and R22 the stage works as expected in
                                          > isolation. Q1
                                          > > > > > inverter also swings 0v to 12v with ptt. Again, all
                                          > resistance
                                          > > > > > measurements taken with Q2 out of circuit look right.
                                          > > > > >
                                          > > > > > Resoldering Q2 into the board the latching problem is
                                          still
                                          > there.
                                          > > > > > Next move is to isolate Q1/2 stages by lifting R24 and
                                          R29.
                                          > > > > >
                                          > > > > > Any more ideas? Sorry to be a pain but this is driving me
                                          > mad!
                                          > > > > >
                                          > > > > > 73,
                                          > > > > > Dave
                                          > > > > >
                                          > > > > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@>
                                          > wrote:
                                          > > > > > >
                                          > > > > > > Thanks Mike,
                                          > > > > > >
                                          > > > > > > I still haven't resolved the issue. The collector of Q1
                                          > waggles
                                          > > > > up
                                          > > > > > > and down with PTT as expected (except that it is only
                                          6V
                                          > ish when
                                          > > > > > PTT
                                          > > > > > > is low instead of the ~12 I would expect). I've double
                                          > checked
                                          > > > > > > soldering and component values. All the 'in circuit'
                                          > resistance
                                          > > > > > > measurements I've taken look reasonable.
                                          > > > > > >
                                          > > > > > > I tried shunting R22 with a resistor from the 12V line
                                          and
                                          > found
                                          > > > > a
                                          > > > > > > value of ~500 ohm would make Q2 unlatch, but it latched
                                          > again
                                          > > > > next
                                          > > > > > > time PTT was taken high.
                                          > > > > > >
                                          > > > > > > I've now pulled Q2 from the circuit and will test it
                                          > tomorrow as
                                          > > > > > well
                                          > > > > > > as checking the circuit around it with it out of
                                          circuit.
                                          > > > > > >
                                          > > > > > > I'll let you know how I get on. I think I'll lash up
                                          the
                                          > same
                                          > > > > > > circuit on the bench and see what happens! It feels a
                                          bit
                                          > like
                                          > > > > > > grasping at straws.
                                          > > > > > >
                                          > > > > > > Regards,
                                          > > > > > >
                                          > > > > > > Dave
                                          > > > > > >
                                          > > > > > > --- In softrock40@yahoogroups.com, "Mike Collins"
                                          > <mikecol@>
                                          > > > > wrote:
                                          > > > > > > >
                                          > > > > > > >
                                          > > > > > > > > Should S12V not follow PTT? Why does /PTT IN reduce
                                          to
                                          > > > > 5V'ish
                                          > > > > > > (the
                                          > > > > > > > > value given in the detailed contruction notes)?
                                          > > > > > > >
                                          > > > > > > > Hi Dave,
                                          > > > > > > >
                                          > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as
                                          an
                                          > > > > > inversion.
                                          > > > > > > >
                                          > > > > > > > The only way for /PTT IN to be lower than 12-0.7V is
                                          for
                                          > Q1 to
                                          > > > > be
                                          > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be
                                          > above .6V or
                                          > > > > > so. I
                                          > > > > > > > would measure across R20 next time it latches up.
                                          > > > > > > >
                                          > > > > > > > R20 is used to drain the voltage on the C27 (at .7V
                                          when
                                          > Q1 ON)
                                          > > > > > down
                                          > > > > > > > to help turn off Q1. With no PTTIN voltage the R20
                                          > voltage
                                          > > > > > should
                                          > > > > > > be
                                          > > > > > > > at 0 V.
                                          > > > > > > >
                                          > > > > > > > Q1 turns on when the PTT IN start going above 1.2V or
                                          > so. This
                                          > > > > > > > happens when the R19/R20 divider starts to go higher
                                          > than .6V;
                                          > > > > > when
                                          > > > > > > > the BE junction starts turning on. When fully on Q1
                                          > collector
                                          > > > > > > should
                                          > > > > > > > be at about .2 V or so.
                                          > > > > > > >
                                          > > > > > > > Q2 does about the opposite: when /PTTIN goes low; the
                                          BE
                                          > > > > junction
                                          > > > > > of
                                          > > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes
                                          close
                                          > to 12V
                                          > > > > > > (i.e.
                                          > > > > > > > 12V - 0.2V).
                                          > > > > > > >
                                          > > > > > > > 73, Mike Collins KF4BQ
                                          > > > > > > >
                                          > > > > > >
                                          > > > > >
                                          > > > >
                                          > > >
                                          > >
                                          >
                                        • Tony Parks
                                          Hi Dave, I will add comments below. I was trying to think what might cause Q7 to fail and looking for the possibility of high current through Q7 where both Q7
                                          Message 20 of 29 , Sep 28, 2008
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                                            Hi Dave,
                                             
                                            I will add comments below.  I was trying to think what might cause Q7 to fail and looking for the possibility of high current through Q7 where both Q7 and Q8 were on at the same time.
                                             
                                            Sorry the v6.3 has been a problem.
                                             
                                            73,
                                            Tony KB9YIG
                                             
                                            ----- Original Message -----
                                            From: g8xul
                                            Sent: Sunday, September 28, 2008 2:20 PM
                                            Subject: [softrock40] Re: Troubleshooting RXTX 6.3

                                            Thanks for reply Tony,

                                            I haven't got the board with me but:

                                            "Please check to make sure C30 is not shorted"
                                            I'll check tomorrow but I haven't got the PA daughter board installed
                                            so C30 only goes to the J2 pin 5 (open circuit).

                                            Ok..

                                            "D2 is mounted with the band end of the diode connected to the base
                                            of Q1."

                                            I've checked this (but will check again) however the collector of Q1
                                            swings 0 to 12 V with the RX switches removed. I'm a bit confused by
                                            the test in the detailed build notes...

                                            "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                            Measure the voltage at R21 hairpin (/PTT-I). This should be ~5 Vdc.."

                                            On my board (with RX switches removed) this voltage is ~12V. When
                                            I've simulated the circuit (in Multisim) it also swings 0 to 12V.

                                             

                                            The collector of Q1 should go to about 12 volts when there is no voltage applied to the PTT IN hole.

                                            73, Dave

                                            --- In softrock40@yahoogro ups.com, "Tony Parks" <kb9yig@...> wrote:
                                            >
                                            > Hi Dave,
                                            >
                                            > Please check to make sure C30 is not shorted and that D2 is mounted
                                            with the band end of the diode connected to the base of Q1.
                                            >
                                            > 73,
                                            > Tony KB9YIG
                                            >
                                            > ----- Original Message -----
                                            > From: g8xul
                                            > To: softrock40@yahoogro ups.com
                                            > Sent: Saturday, September 27, 2008 4:32 PM
                                            > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                            >
                                            >
                                            > Thanks everyone for their helpful comments.
                                            >
                                            > Made some progress yesterday. I removed R29 and R30 to isolate
                                            the
                                            > PTT stage. The S12V line then switched correctly - no latching.
                                            > The /ptt line also swings 0 to 12V.
                                            >
                                            > I removed Q7 and Q8 and found Q7 to be duff. About 600ohms
                                            between
                                            > each terminal. Q8 seems ok although my testing is a bit basic. S
                                            to
                                            > D is high resistance until a finger is used to bias the gate when
                                            it
                                            > falls to a few ohms. Plunging the leads into anti static foam
                                            resets
                                            > it to high impedance.
                                            >
                                            > Resistances around the connections to Q7/8 on the board looked ok.
                                            >
                                            > I replaced Q7 with a new device and powered up the board. The
                                            > latching problem returned and the new Q7 has lost its magic
                                            smoke.
                                            > Same 600ohms between terminals.
                                            >
                                            > I'm going to build the stage in multisim and see if I can try out
                                            > some faults on that.
                                            >
                                            > Back to the debug on Monday. Glad I've got the support of a great
                                            > group.
                                            >
                                            > 73,
                                            >
                                            > Dave
                                            >
                                            > --- In softrock40@yahoogro ups.com, "singhpk99" <singhpk99@> wrote:
                                            > >
                                            > >
                                            > > Please try bypassing C47 and C27 with .1uf and try again
                                            > > If you have it happeing in your rxtx, it may be happening in
                                            mine as
                                            > > well- will check
                                            > >
                                            > > 73s
                                            > >
                                            > > ab2xf
                                            > >
                                            > >
                                            > >
                                            > >
                                            > > --- In softrock40@yahoogro ups.com, "Tim O'Rourke" <w4yn@> wrote:
                                            > > >
                                            > > > Be sure that the wiring to serial port is spot on, so simple
                                            it
                                            > may
                                            > > > have not been obvious. Do not ask how I know this can affect
                                            > keying!
                                            > > > Tim W4YN
                                            > > >
                                            > > > --- In softrock40@yahoogro ups.com, "singhpk99" <singhpk99@>
                                            wrote:
                                            > > > >
                                            > > > >
                                            > > > > It could be oscillating !
                                            > > > >
                                            > > > > Do you have scope?
                                            > > > >
                                            > > > > Please check the Q1, Q2 base and collectors using a scope.
                                            > > > >
                                            > > > > 73s
                                            > > > > Push
                                            > > > > AB2xf
                                            > > > >
                                            > > > >
                                            > > > > --- In softrock40@yahoogro ups.com, "g8xul" <dave.james@ >
                                            wrote:
                                            > > > > >
                                            > > > > > Q2 tests fine. BC and BE junctions look good, 0.65ish
                                            volts
                                            > > > > forward
                                            > > > > > and high impedance reverse biased. Using the same values
                                            as
                                            > the
                                            > > > > > board for R21 and R22 the stage works as expected in
                                            > isolation. Q1
                                            > > > > > inverter also swings 0v to 12v with ptt. Again, all
                                            > resistance
                                            > > > > > measurements taken with Q2 out of circuit look right.
                                            > > > > >
                                            > > > > > Resoldering Q2 into the board the latching problem is
                                            still
                                            > there.
                                            > > > > > Next move is to isolate Q1/2 stages by lifting R24 and
                                            R29.
                                            > > > > >
                                            > > > > > Any more ideas? Sorry to be a pain but this is driving me
                                            > mad!
                                            > > > > >
                                            > > > > > 73,
                                            > > > > > Dave
                                            > > > > >
                                            > > > > > --- In softrock40@yahoogro ups.com, "g8xul" <dave.james@ >
                                            > wrote:
                                            > > > > > >
                                            > > > > > > Thanks Mike,
                                            > > > > > >
                                            > > > > > > I still haven't resolved the issue. The collector of Q1
                                            > waggles
                                            > > > > up
                                            > > > > > > and down with PTT as expected (except that it is only
                                            6V
                                            > ish when
                                            > > > > > PTT
                                            > > > > > > is low instead of the ~12 I would expect). I've double
                                            > checked
                                            > > > > > > soldering and component values. All the 'in circuit'
                                            > resistance
                                            > > > > > > measurements I've taken look reasonable.
                                            > > > > > >
                                            > > > > > > I tried shunting R22 with a resistor from the 12V line
                                            and
                                            > found
                                            > > > > a
                                            > > > > > > value of ~500 ohm would make Q2 unlatch, but it latched
                                            > again
                                            > > > > next
                                            > > > > > > time PTT was taken high.
                                            > > > > > >
                                            > > > > > > I've now pulled Q2 from the circuit and will test it
                                            > tomorrow as
                                            > > > > > well
                                            > > > > > > as checking the circuit around it with it out of
                                            circuit.
                                            > > > > > >
                                            > > > > > > I'll let you know how I get on. I think I'll lash up
                                            the
                                            > same
                                            > > > > > > circuit on the bench and see what happens! It feels a
                                            bit
                                            > like
                                            > > > > > > grasping at straws.
                                            > > > > > >
                                            > > > > > > Regards,
                                            > > > > > >
                                            > > > > > > Dave
                                            > > > > > >
                                            > > > > > > --- In softrock40@yahoogro ups.com, "Mike Collins"
                                            > <mikecol@>
                                            > > > > wrote:
                                            > > > > > > >
                                            > > > > > > >
                                            > > > > > > > > Should S12V not follow PTT? Why does /PTT IN reduce
                                            to
                                            > > > > 5V'ish
                                            > > > > > > (the
                                            > > > > > > > > value given in the detailed contruction notes)?
                                            > > > > > > >
                                            > > > > > > > Hi Dave,
                                            > > > > > > >
                                            > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as
                                            an
                                            > > > > > inversion.
                                            > > > > > > >
                                            > > > > > > > The only way for /PTT IN to be lower than 12-0.7V is
                                            for
                                            > Q1 to
                                            > > > > be
                                            > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be
                                            > above .6V or
                                            > > > > > so. I
                                            > > > > > > > would measure across R20 next time it latches up.
                                            > > > > > > >
                                            > > > > > > > R20 is used to drain the voltage on the C27 (at .7V
                                            when
                                            > Q1 ON)
                                            > > > > > down
                                            > > > > > > > to help turn off Q1. With no PTTIN voltage the R20
                                            > voltage
                                            > > > > > should
                                            > > > > > > be
                                            > > > > > > > at 0 V.
                                            > > > > > > >
                                            > > > > > > > Q1 turns on when the PTT IN start going above 1.2V or
                                            > so. This
                                            > > > > > > > happens when the R19/R20 divider starts to go higher
                                            > than .6V;
                                            > > > > > when
                                            > > > > > > > the BE junction starts turning on. When fully on Q1
                                            > collector
                                            > > > > > > should
                                            > > > > > > > be at about .2 V or so.
                                            > > > > > > >
                                            > > > > > > > Q2 does about the opposite: when /PTTIN goes low; the
                                            BE
                                            > > > > junction
                                            > > > > > of
                                            > > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes
                                            close
                                            > to 12V
                                            > > > > > > (i.e.
                                            > > > > > > > 12V - 0.2V).
                                            > > > > > > >
                                            > > > > > > > 73, Mike Collins KF4BQ
                                            > > > > > > >
                                            > > > > > >
                                            > > > > >
                                            > > > >
                                            > > >
                                            > >
                                            >

                                          • g8xul
                                            Tony, Checked C30 is not shorted. D2 has its band at the top (base Q1). With Q7 / Q8 removed and the board powered I measured with ptt in = 0V /ptt in =
                                            Message 21 of 29 , Sep 29, 2008
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                                              Tony,

                                              Checked C30 is not shorted. D2 has its band at the top (base Q1).

                                              With Q7 / Q8 removed and the board powered I measured

                                              with ptt in = 0V
                                              /ptt in = 11.57V
                                              S12V = 0V
                                              Q7 gate pad = 11.57V
                                              Q7 drain pad = 0V
                                              Q7 source pad = 0V
                                              Q8 gate pad = 0V
                                              Q8 drain pad = 0V
                                              Q8 source pad = 0V

                                              with ptt in = 12V
                                              /ptt in = 0.046V
                                              S12V = 11.47V
                                              Q7 gate pad = 0.047
                                              Q7 drain pad = 0V
                                              Q7 source pad = 0V
                                              Q8 gate pad = 11.47V
                                              Q8 drain pad = 0V
                                              Q8 source pad = 0V

                                              Soldered in 2 new BS170 (robbed from the 160m PA kit). S12V is now
                                              stuck high. Removed R29/30 and in circuit resistance checks suggest
                                              Q7 has blown again.

                                              I'm stumped as to what to try next.

                                              73, Dave
                                              --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@...> wrote:
                                              >
                                              > Hi Dave,
                                              >
                                              > I will add comments below. I was trying to think what might cause
                                              Q7 to fail and looking for the possibility of high current through
                                              Q7 where both Q7 and Q8 were on at the same time.
                                              >
                                              > Sorry the v6.3 has been a problem.
                                              >
                                              > 73,
                                              > Tony KB9YIG
                                              >
                                              > ----- Original Message -----
                                              > From: g8xul
                                              > To: softrock40@yahoogroups.com
                                              > Sent: Sunday, September 28, 2008 2:20 PM
                                              > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                              >
                                              >
                                              > Thanks for reply Tony,
                                              >
                                              > I haven't got the board with me but:
                                              >
                                              > "Please check to make sure C30 is not shorted"
                                              > I'll check tomorrow but I haven't got the PA daughter board
                                              installed
                                              > so C30 only goes to the J2 pin 5 (open circuit).
                                              >
                                              > Ok..
                                              >
                                              > "D2 is mounted with the band end of the diode connected to the
                                              base
                                              > of Q1."
                                              >
                                              > I've checked this (but will check again) however the collector
                                              of Q1
                                              > swings 0 to 12 V with the RX switches removed. I'm a bit
                                              confused by
                                              > the test in the detailed build notes...
                                              >
                                              > "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                              > Measure the voltage at R21 hairpin (/PTT-I). This should be ~5
                                              Vdc.."
                                              >
                                              > On my board (with RX switches removed) this voltage is ~12V.
                                              When
                                              > I've simulated the circuit (in Multisim) it also swings 0 to 12V.
                                              >
                                              >
                                              >
                                              > The collector of Q1 should go to about 12 volts when there is no
                                              voltage applied to the PTT IN hole.
                                              >
                                              > 73, Dave
                                              >
                                              > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
                                              > >
                                              > > Hi Dave,
                                              > >
                                              > > Please check to make sure C30 is not shorted and that D2 is
                                              mounted
                                              > with the band end of the diode connected to the base of Q1.
                                              > >
                                              > > 73,
                                              > > Tony KB9YIG
                                              > >
                                              > > ----- Original Message -----
                                              > > From: g8xul
                                              > > To: softrock40@yahoogroups.com
                                              > > Sent: Saturday, September 27, 2008 4:32 PM
                                              > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                              > >
                                              > >
                                              > > Thanks everyone for their helpful comments.
                                              > >
                                              > > Made some progress yesterday. I removed R29 and R30 to isolate
                                              > the
                                              > > PTT stage. The S12V line then switched correctly - no
                                              latching.
                                              > > The /ptt line also swings 0 to 12V.
                                              > >
                                              > > I removed Q7 and Q8 and found Q7 to be duff. About 600ohms
                                              > between
                                              > > each terminal. Q8 seems ok although my testing is a bit basic.
                                              S
                                              > to
                                              > > D is high resistance until a finger is used to bias the gate
                                              when
                                              > it
                                              > > falls to a few ohms. Plunging the leads into anti static foam
                                              > resets
                                              > > it to high impedance.
                                              > >
                                              > > Resistances around the connections to Q7/8 on the board looked
                                              ok.
                                              > >
                                              > > I replaced Q7 with a new device and powered up the board. The
                                              > > latching problem returned and the new Q7 has lost its magic
                                              > smoke.
                                              > > Same 600ohms between terminals.
                                              > >
                                              > > I'm going to build the stage in multisim and see if I can try
                                              out
                                              > > some faults on that.
                                              > >
                                              > > Back to the debug on Monday. Glad I've got the support of a
                                              great
                                              > > group.
                                              > >
                                              > > 73,
                                              > >
                                              > > Dave
                                              > >
                                              > > --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@>
                                              wrote:
                                              > > >
                                              > > >
                                              > > > Please try bypassing C47 and C27 with .1uf and try again
                                              > > > If you have it happeing in your rxtx, it may be happening in
                                              > mine as
                                              > > > well- will check
                                              > > >
                                              > > > 73s
                                              > > >
                                              > > > ab2xf
                                              > > >
                                              > > >
                                              > > >
                                              > > >
                                              > > > --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@>
                                              wrote:
                                              > > > >
                                              > > > > Be sure that the wiring to serial port is spot on, so
                                              simple
                                              > it
                                              > > may
                                              > > > > have not been obvious. Do not ask how I know this can
                                              affect
                                              > > keying!
                                              > > > > Tim W4YN
                                              > > > >
                                              > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                              <singhpk99@>
                                              > wrote:
                                              > > > > >
                                              > > > > >
                                              > > > > > It could be oscillating !
                                              > > > > >
                                              > > > > > Do you have scope?
                                              > > > > >
                                              > > > > > Please check the Q1, Q2 base and collectors using a
                                              scope.
                                              > > > > >
                                              > > > > > 73s
                                              > > > > > Push
                                              > > > > > AB2xf
                                              > > > > >
                                              > > > > >
                                              > > > > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@>
                                              > wrote:
                                              > > > > > >
                                              > > > > > > Q2 tests fine. BC and BE junctions look good, 0.65ish
                                              > volts
                                              > > > > > forward
                                              > > > > > > and high impedance reverse biased. Using the same
                                              values
                                              > as
                                              > > the
                                              > > > > > > board for R21 and R22 the stage works as expected in
                                              > > isolation. Q1
                                              > > > > > > inverter also swings 0v to 12v with ptt. Again, all
                                              > > resistance
                                              > > > > > > measurements taken with Q2 out of circuit look right.
                                              > > > > > >
                                              > > > > > > Resoldering Q2 into the board the latching problem is
                                              > still
                                              > > there.
                                              > > > > > > Next move is to isolate Q1/2 stages by lifting R24 and
                                              > R29.
                                              > > > > > >
                                              > > > > > > Any more ideas? Sorry to be a pain but this is driving
                                              me
                                              > > mad!
                                              > > > > > >
                                              > > > > > > 73,
                                              > > > > > > Dave
                                              > > > > > >
                                              > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                              <dave.james@>
                                              > > wrote:
                                              > > > > > > >
                                              > > > > > > > Thanks Mike,
                                              > > > > > > >
                                              > > > > > > > I still haven't resolved the issue. The collector of
                                              Q1
                                              > > waggles
                                              > > > > > up
                                              > > > > > > > and down with PTT as expected (except that it is
                                              only
                                              > 6V
                                              > > ish when
                                              > > > > > > PTT
                                              > > > > > > > is low instead of the ~12 I would expect). I've
                                              double
                                              > > checked
                                              > > > > > > > soldering and component values. All the 'in circuit'
                                              > > resistance
                                              > > > > > > > measurements I've taken look reasonable.
                                              > > > > > > >
                                              > > > > > > > I tried shunting R22 with a resistor from the 12V
                                              line
                                              > and
                                              > > found
                                              > > > > > a
                                              > > > > > > > value of ~500 ohm would make Q2 unlatch, but it
                                              latched
                                              > > again
                                              > > > > > next
                                              > > > > > > > time PTT was taken high.
                                              > > > > > > >
                                              > > > > > > > I've now pulled Q2 from the circuit and will test it
                                              > > tomorrow as
                                              > > > > > > well
                                              > > > > > > > as checking the circuit around it with it out of
                                              > circuit.
                                              > > > > > > >
                                              > > > > > > > I'll let you know how I get on. I think I'll lash up
                                              > the
                                              > > same
                                              > > > > > > > circuit on the bench and see what happens! It feels
                                              a
                                              > bit
                                              > > like
                                              > > > > > > > grasping at straws.
                                              > > > > > > >
                                              > > > > > > > Regards,
                                              > > > > > > >
                                              > > > > > > > Dave
                                              > > > > > > >
                                              > > > > > > > --- In softrock40@yahoogroups.com, "Mike Collins"
                                              > > <mikecol@>
                                              > > > > > wrote:
                                              > > > > > > > >
                                              > > > > > > > >
                                              > > > > > > > > > Should S12V not follow PTT? Why does /PTT IN
                                              reduce
                                              > to
                                              > > > > > 5V'ish
                                              > > > > > > > (the
                                              > > > > > > > > > value given in the detailed contruction notes)?
                                              > > > > > > > >
                                              > > > > > > > > Hi Dave,
                                              > > > > > > > >
                                              > > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act
                                              as
                                              > an
                                              > > > > > > inversion.
                                              > > > > > > > >
                                              > > > > > > > > The only way for /PTT IN to be lower than 12-0.7V
                                              is
                                              > for
                                              > > Q1 to
                                              > > > > > be
                                              > > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be
                                              > > above .6V or
                                              > > > > > > so. I
                                              > > > > > > > > would measure across R20 next time it latches up.
                                              > > > > > > > >
                                              > > > > > > > > R20 is used to drain the voltage on the C27
                                              (at .7V
                                              > when
                                              > > Q1 ON)
                                              > > > > > > down
                                              > > > > > > > > to help turn off Q1. With no PTTIN voltage the R20
                                              > > voltage
                                              > > > > > > should
                                              > > > > > > > be
                                              > > > > > > > > at 0 V.
                                              > > > > > > > >
                                              > > > > > > > > Q1 turns on when the PTT IN start going above 1.2V
                                              or
                                              > > so. This
                                              > > > > > > > > happens when the R19/R20 divider starts to go
                                              higher
                                              > > than .6V;
                                              > > > > > > when
                                              > > > > > > > > the BE junction starts turning on. When fully on
                                              Q1
                                              > > collector
                                              > > > > > > > should
                                              > > > > > > > > be at about .2 V or so.
                                              > > > > > > > >
                                              > > > > > > > > Q2 does about the opposite: when /PTTIN goes low;
                                              the
                                              > BE
                                              > > > > > junction
                                              > > > > > > of
                                              > > > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes
                                              > close
                                              > > to 12V
                                              > > > > > > > (i.e.
                                              > > > > > > > > 12V - 0.2V).
                                              > > > > > > > >
                                              > > > > > > > > 73, Mike Collins KF4BQ
                                              > > > > > > > >
                                              > > > > > > >
                                              > > > > > >
                                              > > > > >
                                              > > > >
                                              > > >
                                              > >
                                              >
                                            • singhpk99
                                              Removing R29/30 leaves gate floating- stored charge on gate may toggle it either to on or off. Instead of removing r29/30 short gate to source for q7/q8 to
                                              Message 22 of 29 , Sep 29, 2008
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                                                Removing R29/30 leaves gate floating- stored charge on gate may
                                                toggle it either to on or off. Instead of removing r29/30 short gate
                                                to source for q7/q8 to turn these off. Removing r29/r30 can actually
                                                cause the gate to blow due to static charge accumulation etc.
                                                And please check with a scope to see the dynamic behavior .

                                                Thanks

                                                push/ab2xf

                                                --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
                                                >
                                                > Tony,
                                                >
                                                > Checked C30 is not shorted. D2 has its band at the top (base Q1).
                                                >
                                                > With Q7 / Q8 removed and the board powered I measured
                                                >
                                                > with ptt in = 0V
                                                > /ptt in = 11.57V
                                                > S12V = 0V
                                                > Q7 gate pad = 11.57V
                                                > Q7 drain pad = 0V
                                                > Q7 source pad = 0V
                                                > Q8 gate pad = 0V
                                                > Q8 drain pad = 0V
                                                > Q8 source pad = 0V
                                                >
                                                > with ptt in = 12V
                                                > /ptt in = 0.046V
                                                > S12V = 11.47V
                                                > Q7 gate pad = 0.047
                                                > Q7 drain pad = 0V
                                                > Q7 source pad = 0V
                                                > Q8 gate pad = 11.47V
                                                > Q8 drain pad = 0V
                                                > Q8 source pad = 0V
                                                >
                                                > Soldered in 2 new BS170 (robbed from the 160m PA kit). S12V is now
                                                > stuck high. Removed R29/30 and in circuit resistance checks
                                                suggest
                                                > Q7 has blown again.
                                                >
                                                > I'm stumped as to what to try next.
                                                >
                                                > 73, Dave
                                                > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
                                                > >
                                                > > Hi Dave,
                                                > >
                                                > > I will add comments below. I was trying to think what might
                                                cause
                                                > Q7 to fail and looking for the possibility of high current through
                                                > Q7 where both Q7 and Q8 were on at the same time.
                                                > >
                                                > > Sorry the v6.3 has been a problem.
                                                > >
                                                > > 73,
                                                > > Tony KB9YIG
                                                > >
                                                > > ----- Original Message -----
                                                > > From: g8xul
                                                > > To: softrock40@yahoogroups.com
                                                > > Sent: Sunday, September 28, 2008 2:20 PM
                                                > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                > >
                                                > >
                                                > > Thanks for reply Tony,
                                                > >
                                                > > I haven't got the board with me but:
                                                > >
                                                > > "Please check to make sure C30 is not shorted"
                                                > > I'll check tomorrow but I haven't got the PA daughter board
                                                > installed
                                                > > so C30 only goes to the J2 pin 5 (open circuit).
                                                > >
                                                > > Ok..
                                                > >
                                                > > "D2 is mounted with the band end of the diode connected to the
                                                > base
                                                > > of Q1."
                                                > >
                                                > > I've checked this (but will check again) however the collector
                                                > of Q1
                                                > > swings 0 to 12 V with the RX switches removed. I'm a bit
                                                > confused by
                                                > > the test in the detailed build notes...
                                                > >
                                                > > "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                                > > Measure the voltage at R21 hairpin (/PTT-I). This should be ~5
                                                > Vdc.."
                                                > >
                                                > > On my board (with RX switches removed) this voltage is ~12V.
                                                > When
                                                > > I've simulated the circuit (in Multisim) it also swings 0 to
                                                12V.
                                                > >
                                                > >
                                                > >
                                                > > The collector of Q1 should go to about 12 volts when there is
                                                no
                                                > voltage applied to the PTT IN hole.
                                                > >
                                                > > 73, Dave
                                                > >
                                                > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
                                                > > >
                                                > > > Hi Dave,
                                                > > >
                                                > > > Please check to make sure C30 is not shorted and that D2 is
                                                > mounted
                                                > > with the band end of the diode connected to the base of Q1.
                                                > > >
                                                > > > 73,
                                                > > > Tony KB9YIG
                                                > > >
                                                > > > ----- Original Message -----
                                                > > > From: g8xul
                                                > > > To: softrock40@yahoogroups.com
                                                > > > Sent: Saturday, September 27, 2008 4:32 PM
                                                > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                > > >
                                                > > >
                                                > > > Thanks everyone for their helpful comments.
                                                > > >
                                                > > > Made some progress yesterday. I removed R29 and R30 to
                                                isolate
                                                > > the
                                                > > > PTT stage. The S12V line then switched correctly - no
                                                > latching.
                                                > > > The /ptt line also swings 0 to 12V.
                                                > > >
                                                > > > I removed Q7 and Q8 and found Q7 to be duff. About 600ohms
                                                > > between
                                                > > > each terminal. Q8 seems ok although my testing is a bit
                                                basic.
                                                > S
                                                > > to
                                                > > > D is high resistance until a finger is used to bias the gate
                                                > when
                                                > > it
                                                > > > falls to a few ohms. Plunging the leads into anti static foam
                                                > > resets
                                                > > > it to high impedance.
                                                > > >
                                                > > > Resistances around the connections to Q7/8 on the board
                                                looked
                                                > ok.
                                                > > >
                                                > > > I replaced Q7 with a new device and powered up the board. The
                                                > > > latching problem returned and the new Q7 has lost its magic
                                                > > smoke.
                                                > > > Same 600ohms between terminals.
                                                > > >
                                                > > > I'm going to build the stage in multisim and see if I can try
                                                > out
                                                > > > some faults on that.
                                                > > >
                                                > > > Back to the debug on Monday. Glad I've got the support of a
                                                > great
                                                > > > group.
                                                > > >
                                                > > > 73,
                                                > > >
                                                > > > Dave
                                                > > >
                                                > > > --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@>
                                                > wrote:
                                                > > > >
                                                > > > >
                                                > > > > Please try bypassing C47 and C27 with .1uf and try again
                                                > > > > If you have it happeing in your rxtx, it may be happening
                                                in
                                                > > mine as
                                                > > > > well- will check
                                                > > > >
                                                > > > > 73s
                                                > > > >
                                                > > > > ab2xf
                                                > > > >
                                                > > > >
                                                > > > >
                                                > > > >
                                                > > > > --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@>
                                                > wrote:
                                                > > > > >
                                                > > > > > Be sure that the wiring to serial port is spot on, so
                                                > simple
                                                > > it
                                                > > > may
                                                > > > > > have not been obvious. Do not ask how I know this can
                                                > affect
                                                > > > keying!
                                                > > > > > Tim W4YN
                                                > > > > >
                                                > > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                > <singhpk99@>
                                                > > wrote:
                                                > > > > > >
                                                > > > > > >
                                                > > > > > > It could be oscillating !
                                                > > > > > >
                                                > > > > > > Do you have scope?
                                                > > > > > >
                                                > > > > > > Please check the Q1, Q2 base and collectors using a
                                                > scope.
                                                > > > > > >
                                                > > > > > > 73s
                                                > > > > > > Push
                                                > > > > > > AB2xf
                                                > > > > > >
                                                > > > > > >
                                                > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                <dave.james@>
                                                > > wrote:
                                                > > > > > > >
                                                > > > > > > > Q2 tests fine. BC and BE junctions look good, 0.65ish
                                                > > volts
                                                > > > > > > forward
                                                > > > > > > > and high impedance reverse biased. Using the same
                                                > values
                                                > > as
                                                > > > the
                                                > > > > > > > board for R21 and R22 the stage works as expected in
                                                > > > isolation. Q1
                                                > > > > > > > inverter also swings 0v to 12v with ptt. Again, all
                                                > > > resistance
                                                > > > > > > > measurements taken with Q2 out of circuit look right.
                                                > > > > > > >
                                                > > > > > > > Resoldering Q2 into the board the latching problem is
                                                > > still
                                                > > > there.
                                                > > > > > > > Next move is to isolate Q1/2 stages by lifting R24
                                                and
                                                > > R29.
                                                > > > > > > >
                                                > > > > > > > Any more ideas? Sorry to be a pain but this is
                                                driving
                                                > me
                                                > > > mad!
                                                > > > > > > >
                                                > > > > > > > 73,
                                                > > > > > > > Dave
                                                > > > > > > >
                                                > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                > <dave.james@>
                                                > > > wrote:
                                                > > > > > > > >
                                                > > > > > > > > Thanks Mike,
                                                > > > > > > > >
                                                > > > > > > > > I still haven't resolved the issue. The collector
                                                of
                                                > Q1
                                                > > > waggles
                                                > > > > > > up
                                                > > > > > > > > and down with PTT as expected (except that it is
                                                > only
                                                > > 6V
                                                > > > ish when
                                                > > > > > > > PTT
                                                > > > > > > > > is low instead of the ~12 I would expect). I've
                                                > double
                                                > > > checked
                                                > > > > > > > > soldering and component values. All the 'in
                                                circuit'
                                                > > > resistance
                                                > > > > > > > > measurements I've taken look reasonable.
                                                > > > > > > > >
                                                > > > > > > > > I tried shunting R22 with a resistor from the 12V
                                                > line
                                                > > and
                                                > > > found
                                                > > > > > > a
                                                > > > > > > > > value of ~500 ohm would make Q2 unlatch, but it
                                                > latched
                                                > > > again
                                                > > > > > > next
                                                > > > > > > > > time PTT was taken high.
                                                > > > > > > > >
                                                > > > > > > > > I've now pulled Q2 from the circuit and will test
                                                it
                                                > > > tomorrow as
                                                > > > > > > > well
                                                > > > > > > > > as checking the circuit around it with it out of
                                                > > circuit.
                                                > > > > > > > >
                                                > > > > > > > > I'll let you know how I get on. I think I'll lash
                                                up
                                                > > the
                                                > > > same
                                                > > > > > > > > circuit on the bench and see what happens! It feels
                                                > a
                                                > > bit
                                                > > > like
                                                > > > > > > > > grasping at straws.
                                                > > > > > > > >
                                                > > > > > > > > Regards,
                                                > > > > > > > >
                                                > > > > > > > > Dave
                                                > > > > > > > >
                                                > > > > > > > > --- In softrock40@yahoogroups.com, "Mike Collins"
                                                > > > <mikecol@>
                                                > > > > > > wrote:
                                                > > > > > > > > >
                                                > > > > > > > > >
                                                > > > > > > > > > > Should S12V not follow PTT? Why does /PTT IN
                                                > reduce
                                                > > to
                                                > > > > > > 5V'ish
                                                > > > > > > > > (the
                                                > > > > > > > > > > value given in the detailed contruction notes)?
                                                > > > > > > > > >
                                                > > > > > > > > > Hi Dave,
                                                > > > > > > > > >
                                                > > > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both
                                                act
                                                > as
                                                > > an
                                                > > > > > > > inversion.
                                                > > > > > > > > >
                                                > > > > > > > > > The only way for /PTT IN to be lower than 12-0.7V
                                                > is
                                                > > for
                                                > > > Q1 to
                                                > > > > > > be
                                                > > > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be
                                                > > > above .6V or
                                                > > > > > > > so. I
                                                > > > > > > > > > would measure across R20 next time it latches up.
                                                > > > > > > > > >
                                                > > > > > > > > > R20 is used to drain the voltage on the C27
                                                > (at .7V
                                                > > when
                                                > > > Q1 ON)
                                                > > > > > > > down
                                                > > > > > > > > > to help turn off Q1. With no PTTIN voltage the
                                                R20
                                                > > > voltage
                                                > > > > > > > should
                                                > > > > > > > > be
                                                > > > > > > > > > at 0 V.
                                                > > > > > > > > >
                                                > > > > > > > > > Q1 turns on when the PTT IN start going above
                                                1.2V
                                                > or
                                                > > > so. This
                                                > > > > > > > > > happens when the R19/R20 divider starts to go
                                                > higher
                                                > > > than .6V;
                                                > > > > > > > when
                                                > > > > > > > > > the BE junction starts turning on. When fully on
                                                > Q1
                                                > > > collector
                                                > > > > > > > > should
                                                > > > > > > > > > be at about .2 V or so.
                                                > > > > > > > > >
                                                > > > > > > > > > Q2 does about the opposite: when /PTTIN goes low;
                                                > the
                                                > > BE
                                                > > > > > > junction
                                                > > > > > > > of
                                                > > > > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V
                                                goes
                                                > > close
                                                > > > to 12V
                                                > > > > > > > > (i.e.
                                                > > > > > > > > > 12V - 0.2V).
                                                > > > > > > > > >
                                                > > > > > > > > > 73, Mike Collins KF4BQ
                                                > > > > > > > > >
                                                > > > > > > > >
                                                > > > > > > >
                                                > > > > > >
                                                > > > > >
                                                > > > >
                                                > > >
                                                > >
                                                >
                                              • Tim O'Rourke
                                                Do you have the antenna connected when Q7 goes south? If so ck that the connections for antenna on PCB are not reversed Tim W4YN ... suggest ... cause ...
                                                Message 23 of 29 , Sep 29, 2008
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                                                  Do you have the antenna connected when Q7 goes south? If so ck that
                                                  the connections for antenna on PCB are not reversed>
                                                  Tim W4YN
                                                  --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
                                                  >
                                                  > Tony,
                                                  >
                                                  > Checked C30 is not shorted. D2 has its band at the top (base Q1).
                                                  >
                                                  > With Q7 / Q8 removed and the board powered I measured
                                                  >
                                                  > with ptt in = 0V
                                                  > /ptt in = 11.57V
                                                  > S12V = 0V
                                                  > Q7 gate pad = 11.57V
                                                  > Q7 drain pad = 0V
                                                  > Q7 source pad = 0V
                                                  > Q8 gate pad = 0V
                                                  > Q8 drain pad = 0V
                                                  > Q8 source pad = 0V
                                                  >
                                                  > with ptt in = 12V
                                                  > /ptt in = 0.046V
                                                  > S12V = 11.47V
                                                  > Q7 gate pad = 0.047
                                                  > Q7 drain pad = 0V
                                                  > Q7 source pad = 0V
                                                  > Q8 gate pad = 11.47V
                                                  > Q8 drain pad = 0V
                                                  > Q8 source pad = 0V
                                                  >
                                                  > Soldered in 2 new BS170 (robbed from the 160m PA kit). S12V is now
                                                  > stuck high. Removed R29/30 and in circuit resistance checks
                                                  suggest
                                                  > Q7 has blown again.
                                                  >
                                                  > I'm stumped as to what to try next.
                                                  >
                                                  > 73, Dave
                                                  > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
                                                  > >
                                                  > > Hi Dave,
                                                  > >
                                                  > > I will add comments below. I was trying to think what might
                                                  cause
                                                  > Q7 to fail and looking for the possibility of high current through
                                                  > Q7 where both Q7 and Q8 were on at the same time.
                                                  > >
                                                  > > Sorry the v6.3 has been a problem.
                                                  > >
                                                  > > 73,
                                                  > > Tony KB9YIG
                                                  > >
                                                  > > ----- Original Message -----
                                                  > > From: g8xul
                                                  > > To: softrock40@yahoogroups.com
                                                  > > Sent: Sunday, September 28, 2008 2:20 PM
                                                  > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                  > >
                                                  > >
                                                  > > Thanks for reply Tony,
                                                  > >
                                                  > > I haven't got the board with me but:
                                                  > >
                                                  > > "Please check to make sure C30 is not shorted"
                                                  > > I'll check tomorrow but I haven't got the PA daughter board
                                                  > installed
                                                  > > so C30 only goes to the J2 pin 5 (open circuit).
                                                  > >
                                                  > > Ok..
                                                  > >
                                                  > > "D2 is mounted with the band end of the diode connected to the
                                                  > base
                                                  > > of Q1."
                                                  > >
                                                  > > I've checked this (but will check again) however the collector
                                                  > of Q1
                                                  > > swings 0 to 12 V with the RX switches removed. I'm a bit
                                                  > confused by
                                                  > > the test in the detailed build notes...
                                                  > >
                                                  > > "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                                  > > Measure the voltage at R21 hairpin (/PTT-I). This should be ~5
                                                  > Vdc.."
                                                  > >
                                                  > > On my board (with RX switches removed) this voltage is ~12V.
                                                  > When
                                                  > > I've simulated the circuit (in Multisim) it also swings 0 to
                                                  12V.
                                                  > >
                                                  > >
                                                  > >
                                                  > > The collector of Q1 should go to about 12 volts when there is
                                                  no
                                                  > voltage applied to the PTT IN hole.
                                                  > >
                                                  > > 73, Dave
                                                  > >
                                                  > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
                                                  > > >
                                                  > > > Hi Dave,
                                                  > > >
                                                  > > > Please check to make sure C30 is not shorted and that D2 is
                                                  > mounted
                                                  > > with the band end of the diode connected to the base of Q1.
                                                  > > >
                                                  > > > 73,
                                                  > > > Tony KB9YIG
                                                  > > >
                                                  > > > ----- Original Message -----
                                                  > > > From: g8xul
                                                  > > > To: softrock40@yahoogroups.com
                                                  > > > Sent: Saturday, September 27, 2008 4:32 PM
                                                  > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                  > > >
                                                  > > >
                                                  > > > Thanks everyone for their helpful comments.
                                                  > > >
                                                  > > > Made some progress yesterday. I removed R29 and R30 to
                                                  isolate
                                                  > > the
                                                  > > > PTT stage. The S12V line then switched correctly - no
                                                  > latching.
                                                  > > > The /ptt line also swings 0 to 12V.
                                                  > > >
                                                  > > > I removed Q7 and Q8 and found Q7 to be duff. About 600ohms
                                                  > > between
                                                  > > > each terminal. Q8 seems ok although my testing is a bit
                                                  basic.
                                                  > S
                                                  > > to
                                                  > > > D is high resistance until a finger is used to bias the gate
                                                  > when
                                                  > > it
                                                  > > > falls to a few ohms. Plunging the leads into anti static foam
                                                  > > resets
                                                  > > > it to high impedance.
                                                  > > >
                                                  > > > Resistances around the connections to Q7/8 on the board
                                                  looked
                                                  > ok.
                                                  > > >
                                                  > > > I replaced Q7 with a new device and powered up the board. The
                                                  > > > latching problem returned and the new Q7 has lost its magic
                                                  > > smoke.
                                                  > > > Same 600ohms between terminals.
                                                  > > >
                                                  > > > I'm going to build the stage in multisim and see if I can try
                                                  > out
                                                  > > > some faults on that.
                                                  > > >
                                                  > > > Back to the debug on Monday. Glad I've got the support of a
                                                  > great
                                                  > > > group.
                                                  > > >
                                                  > > > 73,
                                                  > > >
                                                  > > > Dave
                                                  > > >
                                                  > > > --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@>
                                                  > wrote:
                                                  > > > >
                                                  > > > >
                                                  > > > > Please try bypassing C47 and C27 with .1uf and try again
                                                  > > > > If you have it happeing in your rxtx, it may be happening
                                                  in
                                                  > > mine as
                                                  > > > > well- will check
                                                  > > > >
                                                  > > > > 73s
                                                  > > > >
                                                  > > > > ab2xf
                                                  > > > >
                                                  > > > >
                                                  > > > >
                                                  > > > >
                                                  > > > > --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@>
                                                  > wrote:
                                                  > > > > >
                                                  > > > > > Be sure that the wiring to serial port is spot on, so
                                                  > simple
                                                  > > it
                                                  > > > may
                                                  > > > > > have not been obvious. Do not ask how I know this can
                                                  > affect
                                                  > > > keying!
                                                  > > > > > Tim W4YN
                                                  > > > > >
                                                  > > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                  > <singhpk99@>
                                                  > > wrote:
                                                  > > > > > >
                                                  > > > > > >
                                                  > > > > > > It could be oscillating !
                                                  > > > > > >
                                                  > > > > > > Do you have scope?
                                                  > > > > > >
                                                  > > > > > > Please check the Q1, Q2 base and collectors using a
                                                  > scope.
                                                  > > > > > >
                                                  > > > > > > 73s
                                                  > > > > > > Push
                                                  > > > > > > AB2xf
                                                  > > > > > >
                                                  > > > > > >
                                                  > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                  <dave.james@>
                                                  > > wrote:
                                                  > > > > > > >
                                                  > > > > > > > Q2 tests fine. BC and BE junctions look good, 0.65ish
                                                  > > volts
                                                  > > > > > > forward
                                                  > > > > > > > and high impedance reverse biased. Using the same
                                                  > values
                                                  > > as
                                                  > > > the
                                                  > > > > > > > board for R21 and R22 the stage works as expected in
                                                  > > > isolation. Q1
                                                  > > > > > > > inverter also swings 0v to 12v with ptt. Again, all
                                                  > > > resistance
                                                  > > > > > > > measurements taken with Q2 out of circuit look right.
                                                  > > > > > > >
                                                  > > > > > > > Resoldering Q2 into the board the latching problem is
                                                  > > still
                                                  > > > there.
                                                  > > > > > > > Next move is to isolate Q1/2 stages by lifting R24
                                                  and
                                                  > > R29.
                                                  > > > > > > >
                                                  > > > > > > > Any more ideas? Sorry to be a pain but this is
                                                  driving
                                                  > me
                                                  > > > mad!
                                                  > > > > > > >
                                                  > > > > > > > 73,
                                                  > > > > > > > Dave
                                                  > > > > > > >
                                                  > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                  > <dave.james@>
                                                  > > > wrote:
                                                  > > > > > > > >
                                                  > > > > > > > > Thanks Mike,
                                                  > > > > > > > >
                                                  > > > > > > > > I still haven't resolved the issue. The collector
                                                  of
                                                  > Q1
                                                  > > > waggles
                                                  > > > > > > up
                                                  > > > > > > > > and down with PTT as expected (except that it is
                                                  > only
                                                  > > 6V
                                                  > > > ish when
                                                  > > > > > > > PTT
                                                  > > > > > > > > is low instead of the ~12 I would expect). I've
                                                  > double
                                                  > > > checked
                                                  > > > > > > > > soldering and component values. All the 'in
                                                  circuit'
                                                  > > > resistance
                                                  > > > > > > > > measurements I've taken look reasonable.
                                                  > > > > > > > >
                                                  > > > > > > > > I tried shunting R22 with a resistor from the 12V
                                                  > line
                                                  > > and
                                                  > > > found
                                                  > > > > > > a
                                                  > > > > > > > > value of ~500 ohm would make Q2 unlatch, but it
                                                  > latched
                                                  > > > again
                                                  > > > > > > next
                                                  > > > > > > > > time PTT was taken high.
                                                  > > > > > > > >
                                                  > > > > > > > > I've now pulled Q2 from the circuit and will test
                                                  it
                                                  > > > tomorrow as
                                                  > > > > > > > well
                                                  > > > > > > > > as checking the circuit around it with it out of
                                                  > > circuit.
                                                  > > > > > > > >
                                                  > > > > > > > > I'll let you know how I get on. I think I'll lash
                                                  up
                                                  > > the
                                                  > > > same
                                                  > > > > > > > > circuit on the bench and see what happens! It feels
                                                  > a
                                                  > > bit
                                                  > > > like
                                                  > > > > > > > > grasping at straws.
                                                  > > > > > > > >
                                                  > > > > > > > > Regards,
                                                  > > > > > > > >
                                                  > > > > > > > > Dave
                                                  > > > > > > > >
                                                  > > > > > > > > --- In softrock40@yahoogroups.com, "Mike Collins"
                                                  > > > <mikecol@>
                                                  > > > > > > wrote:
                                                  > > > > > > > > >
                                                  > > > > > > > > >
                                                  > > > > > > > > > > Should S12V not follow PTT? Why does /PTT IN
                                                  > reduce
                                                  > > to
                                                  > > > > > > 5V'ish
                                                  > > > > > > > > (the
                                                  > > > > > > > > > > value given in the detailed contruction notes)?
                                                  > > > > > > > > >
                                                  > > > > > > > > > Hi Dave,
                                                  > > > > > > > > >
                                                  > > > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both
                                                  act
                                                  > as
                                                  > > an
                                                  > > > > > > > inversion.
                                                  > > > > > > > > >
                                                  > > > > > > > > > The only way for /PTT IN to be lower than 12-0.7V
                                                  > is
                                                  > > for
                                                  > > > Q1 to
                                                  > > > > > > be
                                                  > > > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must be
                                                  > > > above .6V or
                                                  > > > > > > > so. I
                                                  > > > > > > > > > would measure across R20 next time it latches up.
                                                  > > > > > > > > >
                                                  > > > > > > > > > R20 is used to drain the voltage on the C27
                                                  > (at .7V
                                                  > > when
                                                  > > > Q1 ON)
                                                  > > > > > > > down
                                                  > > > > > > > > > to help turn off Q1. With no PTTIN voltage the
                                                  R20
                                                  > > > voltage
                                                  > > > > > > > should
                                                  > > > > > > > > be
                                                  > > > > > > > > > at 0 V.
                                                  > > > > > > > > >
                                                  > > > > > > > > > Q1 turns on when the PTT IN start going above
                                                  1.2V
                                                  > or
                                                  > > > so. This
                                                  > > > > > > > > > happens when the R19/R20 divider starts to go
                                                  > higher
                                                  > > > than .6V;
                                                  > > > > > > > when
                                                  > > > > > > > > > the BE junction starts turning on. When fully on
                                                  > Q1
                                                  > > > collector
                                                  > > > > > > > > should
                                                  > > > > > > > > > be at about .2 V or so.
                                                  > > > > > > > > >
                                                  > > > > > > > > > Q2 does about the opposite: when /PTTIN goes low;
                                                  > the
                                                  > > BE
                                                  > > > > > > junction
                                                  > > > > > > > of
                                                  > > > > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V
                                                  goes
                                                  > > close
                                                  > > > to 12V
                                                  > > > > > > > > (i.e.
                                                  > > > > > > > > > 12V - 0.2V).
                                                  > > > > > > > > >
                                                  > > > > > > > > > 73, Mike Collins KF4BQ
                                                  > > > > > > > > >
                                                  > > > > > > > >
                                                  > > > > > > >
                                                  > > > > > >
                                                  > > > > >
                                                  > > > >
                                                  > > >
                                                  > >
                                                  >
                                                • g8xul
                                                  Hi Tim, I ve been testing without the RxBPF installed. Could this be the problem? I guess the BPF provides a transient route to earth for the source of Q7.
                                                  Message 24 of 29 , Sep 30, 2008
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                                                    Hi Tim,

                                                    I've been testing without the RxBPF installed. Could this be the
                                                    problem? I guess the BPF provides a transient route to earth for
                                                    the source of Q7.

                                                    The main board has a short length of hookup coax connected to the
                                                    Ant pads and this is not short inner to outer.

                                                    73, Dave

                                                    --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@...> wrote:
                                                    >
                                                    > Do you have the antenna connected when Q7 goes south? If so ck
                                                    that
                                                    > the connections for antenna on PCB are not reversed>
                                                    > Tim W4YN
                                                    > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                                    > >
                                                    > > Tony,
                                                    > >
                                                    > > Checked C30 is not shorted. D2 has its band at the top (base
                                                    Q1).
                                                    > >
                                                    > > With Q7 / Q8 removed and the board powered I measured
                                                    > >
                                                    > > with ptt in = 0V
                                                    > > /ptt in = 11.57V
                                                    > > S12V = 0V
                                                    > > Q7 gate pad = 11.57V
                                                    > > Q7 drain pad = 0V
                                                    > > Q7 source pad = 0V
                                                    > > Q8 gate pad = 0V
                                                    > > Q8 drain pad = 0V
                                                    > > Q8 source pad = 0V
                                                    > >
                                                    > > with ptt in = 12V
                                                    > > /ptt in = 0.046V
                                                    > > S12V = 11.47V
                                                    > > Q7 gate pad = 0.047
                                                    > > Q7 drain pad = 0V
                                                    > > Q7 source pad = 0V
                                                    > > Q8 gate pad = 11.47V
                                                    > > Q8 drain pad = 0V
                                                    > > Q8 source pad = 0V
                                                    > >
                                                    > > Soldered in 2 new BS170 (robbed from the 160m PA kit). S12V is
                                                    now
                                                    > > stuck high. Removed R29/30 and in circuit resistance checks
                                                    > suggest
                                                    > > Q7 has blown again.
                                                    > >
                                                    > > I'm stumped as to what to try next.
                                                    > >
                                                    > > 73, Dave
                                                    > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
                                                    > > >
                                                    > > > Hi Dave,
                                                    > > >
                                                    > > > I will add comments below. I was trying to think what might
                                                    > cause
                                                    > > Q7 to fail and looking for the possibility of high current
                                                    through
                                                    > > Q7 where both Q7 and Q8 were on at the same time.
                                                    > > >
                                                    > > > Sorry the v6.3 has been a problem.
                                                    > > >
                                                    > > > 73,
                                                    > > > Tony KB9YIG
                                                    > > >
                                                    > > > ----- Original Message -----
                                                    > > > From: g8xul
                                                    > > > To: softrock40@yahoogroups.com
                                                    > > > Sent: Sunday, September 28, 2008 2:20 PM
                                                    > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                    > > >
                                                    > > >
                                                    > > > Thanks for reply Tony,
                                                    > > >
                                                    > > > I haven't got the board with me but:
                                                    > > >
                                                    > > > "Please check to make sure C30 is not shorted"
                                                    > > > I'll check tomorrow but I haven't got the PA daughter board
                                                    > > installed
                                                    > > > so C30 only goes to the J2 pin 5 (open circuit).
                                                    > > >
                                                    > > > Ok..
                                                    > > >
                                                    > > > "D2 is mounted with the band end of the diode connected to
                                                    the
                                                    > > base
                                                    > > > of Q1."
                                                    > > >
                                                    > > > I've checked this (but will check again) however the
                                                    collector
                                                    > > of Q1
                                                    > > > swings 0 to 12 V with the RX switches removed. I'm a bit
                                                    > > confused by
                                                    > > > the test in the detailed build notes...
                                                    > > >
                                                    > > > "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                                    > > > Measure the voltage at R21 hairpin (/PTT-I). This should be
                                                    ~5
                                                    > > Vdc.."
                                                    > > >
                                                    > > > On my board (with RX switches removed) this voltage is ~12V.
                                                    > > When
                                                    > > > I've simulated the circuit (in Multisim) it also swings 0 to
                                                    > 12V.
                                                    > > >
                                                    > > >
                                                    > > >
                                                    > > > The collector of Q1 should go to about 12 volts when there
                                                    is
                                                    > no
                                                    > > voltage applied to the PTT IN hole.
                                                    > > >
                                                    > > > 73, Dave
                                                    > > >
                                                    > > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@>
                                                    wrote:
                                                    > > > >
                                                    > > > > Hi Dave,
                                                    > > > >
                                                    > > > > Please check to make sure C30 is not shorted and that D2
                                                    is
                                                    > > mounted
                                                    > > > with the band end of the diode connected to the base of Q1.
                                                    > > > >
                                                    > > > > 73,
                                                    > > > > Tony KB9YIG
                                                    > > > >
                                                    > > > > ----- Original Message -----
                                                    > > > > From: g8xul
                                                    > > > > To: softrock40@yahoogroups.com
                                                    > > > > Sent: Saturday, September 27, 2008 4:32 PM
                                                    > > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                    > > > >
                                                    > > > >
                                                    > > > > Thanks everyone for their helpful comments.
                                                    > > > >
                                                    > > > > Made some progress yesterday. I removed R29 and R30 to
                                                    > isolate
                                                    > > > the
                                                    > > > > PTT stage. The S12V line then switched correctly - no
                                                    > > latching.
                                                    > > > > The /ptt line also swings 0 to 12V.
                                                    > > > >
                                                    > > > > I removed Q7 and Q8 and found Q7 to be duff. About 600ohms
                                                    > > > between
                                                    > > > > each terminal. Q8 seems ok although my testing is a bit
                                                    > basic.
                                                    > > S
                                                    > > > to
                                                    > > > > D is high resistance until a finger is used to bias the
                                                    gate
                                                    > > when
                                                    > > > it
                                                    > > > > falls to a few ohms. Plunging the leads into anti static
                                                    foam
                                                    > > > resets
                                                    > > > > it to high impedance.
                                                    > > > >
                                                    > > > > Resistances around the connections to Q7/8 on the board
                                                    > looked
                                                    > > ok.
                                                    > > > >
                                                    > > > > I replaced Q7 with a new device and powered up the board.
                                                    The
                                                    > > > > latching problem returned and the new Q7 has lost its
                                                    magic
                                                    > > > smoke.
                                                    > > > > Same 600ohms between terminals.
                                                    > > > >
                                                    > > > > I'm going to build the stage in multisim and see if I can
                                                    try
                                                    > > out
                                                    > > > > some faults on that.
                                                    > > > >
                                                    > > > > Back to the debug on Monday. Glad I've got the support of
                                                    a
                                                    > > great
                                                    > > > > group.
                                                    > > > >
                                                    > > > > 73,
                                                    > > > >
                                                    > > > > Dave
                                                    > > > >
                                                    > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                    <singhpk99@>
                                                    > > wrote:
                                                    > > > > >
                                                    > > > > >
                                                    > > > > > Please try bypassing C47 and C27 with .1uf and try again
                                                    > > > > > If you have it happeing in your rxtx, it may be
                                                    happening
                                                    > in
                                                    > > > mine as
                                                    > > > > > well- will check
                                                    > > > > >
                                                    > > > > > 73s
                                                    > > > > >
                                                    > > > > > ab2xf
                                                    > > > > >
                                                    > > > > >
                                                    > > > > >
                                                    > > > > >
                                                    > > > > > --- In softrock40@yahoogroups.com, "Tim O'Rourke"
                                                    <w4yn@>
                                                    > > wrote:
                                                    > > > > > >
                                                    > > > > > > Be sure that the wiring to serial port is spot on, so
                                                    > > simple
                                                    > > > it
                                                    > > > > may
                                                    > > > > > > have not been obvious. Do not ask how I know this can
                                                    > > affect
                                                    > > > > keying!
                                                    > > > > > > Tim W4YN
                                                    > > > > > >
                                                    > > > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                    > > <singhpk99@>
                                                    > > > wrote:
                                                    > > > > > > >
                                                    > > > > > > >
                                                    > > > > > > > It could be oscillating !
                                                    > > > > > > >
                                                    > > > > > > > Do you have scope?
                                                    > > > > > > >
                                                    > > > > > > > Please check the Q1, Q2 base and collectors using a
                                                    > > scope.
                                                    > > > > > > >
                                                    > > > > > > > 73s
                                                    > > > > > > > Push
                                                    > > > > > > > AB2xf
                                                    > > > > > > >
                                                    > > > > > > >
                                                    > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                    > <dave.james@>
                                                    > > > wrote:
                                                    > > > > > > > >
                                                    > > > > > > > > Q2 tests fine. BC and BE junctions look good,
                                                    0.65ish
                                                    > > > volts
                                                    > > > > > > > forward
                                                    > > > > > > > > and high impedance reverse biased. Using the same
                                                    > > values
                                                    > > > as
                                                    > > > > the
                                                    > > > > > > > > board for R21 and R22 the stage works as expected
                                                    in
                                                    > > > > isolation. Q1
                                                    > > > > > > > > inverter also swings 0v to 12v with ptt. Again,
                                                    all
                                                    > > > > resistance
                                                    > > > > > > > > measurements taken with Q2 out of circuit look
                                                    right.
                                                    > > > > > > > >
                                                    > > > > > > > > Resoldering Q2 into the board the latching problem
                                                    is
                                                    > > > still
                                                    > > > > there.
                                                    > > > > > > > > Next move is to isolate Q1/2 stages by lifting R24
                                                    > and
                                                    > > > R29.
                                                    > > > > > > > >
                                                    > > > > > > > > Any more ideas? Sorry to be a pain but this is
                                                    > driving
                                                    > > me
                                                    > > > > mad!
                                                    > > > > > > > >
                                                    > > > > > > > > 73,
                                                    > > > > > > > > Dave
                                                    > > > > > > > >
                                                    > > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                    > > <dave.james@>
                                                    > > > > wrote:
                                                    > > > > > > > > >
                                                    > > > > > > > > > Thanks Mike,
                                                    > > > > > > > > >
                                                    > > > > > > > > > I still haven't resolved the issue. The
                                                    collector
                                                    > of
                                                    > > Q1
                                                    > > > > waggles
                                                    > > > > > > > up
                                                    > > > > > > > > > and down with PTT as expected (except that it is
                                                    > > only
                                                    > > > 6V
                                                    > > > > ish when
                                                    > > > > > > > > PTT
                                                    > > > > > > > > > is low instead of the ~12 I would expect). I've
                                                    > > double
                                                    > > > > checked
                                                    > > > > > > > > > soldering and component values. All the 'in
                                                    > circuit'
                                                    > > > > resistance
                                                    > > > > > > > > > measurements I've taken look reasonable.
                                                    > > > > > > > > >
                                                    > > > > > > > > > I tried shunting R22 with a resistor from the
                                                    12V
                                                    > > line
                                                    > > > and
                                                    > > > > found
                                                    > > > > > > > a
                                                    > > > > > > > > > value of ~500 ohm would make Q2 unlatch, but it
                                                    > > latched
                                                    > > > > again
                                                    > > > > > > > next
                                                    > > > > > > > > > time PTT was taken high.
                                                    > > > > > > > > >
                                                    > > > > > > > > > I've now pulled Q2 from the circuit and will
                                                    test
                                                    > it
                                                    > > > > tomorrow as
                                                    > > > > > > > > well
                                                    > > > > > > > > > as checking the circuit around it with it out of
                                                    > > > circuit.
                                                    > > > > > > > > >
                                                    > > > > > > > > > I'll let you know how I get on. I think I'll
                                                    lash
                                                    > up
                                                    > > > the
                                                    > > > > same
                                                    > > > > > > > > > circuit on the bench and see what happens! It
                                                    feels
                                                    > > a
                                                    > > > bit
                                                    > > > > like
                                                    > > > > > > > > > grasping at straws.
                                                    > > > > > > > > >
                                                    > > > > > > > > > Regards,
                                                    > > > > > > > > >
                                                    > > > > > > > > > Dave
                                                    > > > > > > > > >
                                                    > > > > > > > > > --- In softrock40@yahoogroups.com, "Mike
                                                    Collins"
                                                    > > > > <mikecol@>
                                                    > > > > > > > wrote:
                                                    > > > > > > > > > >
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > > Should S12V not follow PTT? Why does /PTT IN
                                                    > > reduce
                                                    > > > to
                                                    > > > > > > > 5V'ish
                                                    > > > > > > > > > (the
                                                    > > > > > > > > > > > value given in the detailed contruction
                                                    notes)?
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > Hi Dave,
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both
                                                    > act
                                                    > > as
                                                    > > > an
                                                    > > > > > > > > inversion.
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > The only way for /PTT IN to be lower than 12-
                                                    0.7V
                                                    > > is
                                                    > > > for
                                                    > > > > Q1 to
                                                    > > > > > > > be
                                                    > > > > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must
                                                    be
                                                    > > > > above .6V or
                                                    > > > > > > > > so. I
                                                    > > > > > > > > > > would measure across R20 next time it latches
                                                    up.
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > R20 is used to drain the voltage on the C27
                                                    > > (at .7V
                                                    > > > when
                                                    > > > > Q1 ON)
                                                    > > > > > > > > down
                                                    > > > > > > > > > > to help turn off Q1. With no PTTIN voltage the
                                                    > R20
                                                    > > > > voltage
                                                    > > > > > > > > should
                                                    > > > > > > > > > be
                                                    > > > > > > > > > > at 0 V.
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > Q1 turns on when the PTT IN start going above
                                                    > 1.2V
                                                    > > or
                                                    > > > > so. This
                                                    > > > > > > > > > > happens when the R19/R20 divider starts to go
                                                    > > higher
                                                    > > > > than .6V;
                                                    > > > > > > > > when
                                                    > > > > > > > > > > the BE junction starts turning on. When fully
                                                    on
                                                    > > Q1
                                                    > > > > collector
                                                    > > > > > > > > > should
                                                    > > > > > > > > > > be at about .2 V or so.
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > Q2 does about the opposite: when /PTTIN goes
                                                    low;
                                                    > > the
                                                    > > > BE
                                                    > > > > > > > junction
                                                    > > > > > > > > of
                                                    > > > > > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V
                                                    > goes
                                                    > > > close
                                                    > > > > to 12V
                                                    > > > > > > > > > (i.e.
                                                    > > > > > > > > > > 12V - 0.2V).
                                                    > > > > > > > > > >
                                                    > > > > > > > > > > 73, Mike Collins KF4BQ
                                                    > > > > > > > > > >
                                                    > > > > > > > > >
                                                    > > > > > > > >
                                                    > > > > > > >
                                                    > > > > > >
                                                    > > > > >
                                                    > > > >
                                                    > > >
                                                    > >
                                                    >
                                                  • Tim O'Rourke
                                                    Not sure about testing with BPF out will need to ponder that. It was just a random thouht. I assume you are testing with serial cable connected to PC. Double
                                                    Message 25 of 29 , Sep 30, 2008
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                                                      Not sure about testing with BPF out will need to ponder that. It was
                                                      just a random thouht. I assume you are testing with serial cable
                                                      connected to PC. Double check wiring to db9 I had one wire reversed
                                                      and it drove me crazy for a day troubleshooting the PPT as you are.
                                                      Tim
                                                      --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
                                                      >
                                                      > Hi Tim,
                                                      >
                                                      > I've been testing without the RxBPF installed. Could this be the
                                                      > problem? I guess the BPF provides a transient route to earth for
                                                      > the source of Q7.
                                                      >
                                                      > The main board has a short length of hookup coax connected to the
                                                      > Ant pads and this is not short inner to outer.
                                                      >
                                                      > 73, Dave
                                                      >
                                                      > --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@> wrote:
                                                      > >
                                                      > > Do you have the antenna connected when Q7 goes south? If so ck
                                                      > that
                                                      > > the connections for antenna on PCB are not reversed>
                                                      > > Tim W4YN
                                                      > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                                      > > >
                                                      > > > Tony,
                                                      > > >
                                                      > > > Checked C30 is not shorted. D2 has its band at the top (base
                                                      > Q1).
                                                      > > >
                                                      > > > With Q7 / Q8 removed and the board powered I measured
                                                      > > >
                                                      > > > with ptt in = 0V
                                                      > > > /ptt in = 11.57V
                                                      > > > S12V = 0V
                                                      > > > Q7 gate pad = 11.57V
                                                      > > > Q7 drain pad = 0V
                                                      > > > Q7 source pad = 0V
                                                      > > > Q8 gate pad = 0V
                                                      > > > Q8 drain pad = 0V
                                                      > > > Q8 source pad = 0V
                                                      > > >
                                                      > > > with ptt in = 12V
                                                      > > > /ptt in = 0.046V
                                                      > > > S12V = 11.47V
                                                      > > > Q7 gate pad = 0.047
                                                      > > > Q7 drain pad = 0V
                                                      > > > Q7 source pad = 0V
                                                      > > > Q8 gate pad = 11.47V
                                                      > > > Q8 drain pad = 0V
                                                      > > > Q8 source pad = 0V
                                                      > > >
                                                      > > > Soldered in 2 new BS170 (robbed from the 160m PA kit). S12V is
                                                      > now
                                                      > > > stuck high. Removed R29/30 and in circuit resistance checks
                                                      > > suggest
                                                      > > > Q7 has blown again.
                                                      > > >
                                                      > > > I'm stumped as to what to try next.
                                                      > > >
                                                      > > > 73, Dave
                                                      > > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@> wrote:
                                                      > > > >
                                                      > > > > Hi Dave,
                                                      > > > >
                                                      > > > > I will add comments below. I was trying to think what might
                                                      > > cause
                                                      > > > Q7 to fail and looking for the possibility of high current
                                                      > through
                                                      > > > Q7 where both Q7 and Q8 were on at the same time.
                                                      > > > >
                                                      > > > > Sorry the v6.3 has been a problem.
                                                      > > > >
                                                      > > > > 73,
                                                      > > > > Tony KB9YIG
                                                      > > > >
                                                      > > > > ----- Original Message -----
                                                      > > > > From: g8xul
                                                      > > > > To: softrock40@yahoogroups.com
                                                      > > > > Sent: Sunday, September 28, 2008 2:20 PM
                                                      > > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                      > > > >
                                                      > > > >
                                                      > > > > Thanks for reply Tony,
                                                      > > > >
                                                      > > > > I haven't got the board with me but:
                                                      > > > >
                                                      > > > > "Please check to make sure C30 is not shorted"
                                                      > > > > I'll check tomorrow but I haven't got the PA daughter board
                                                      > > > installed
                                                      > > > > so C30 only goes to the J2 pin 5 (open circuit).
                                                      > > > >
                                                      > > > > Ok..
                                                      > > > >
                                                      > > > > "D2 is mounted with the band end of the diode connected to
                                                      > the
                                                      > > > base
                                                      > > > > of Q1."
                                                      > > > >
                                                      > > > > I've checked this (but will check again) however the
                                                      > collector
                                                      > > > of Q1
                                                      > > > > swings 0 to 12 V with the RX switches removed. I'm a bit
                                                      > > > confused by
                                                      > > > > the test in the detailed build notes...
                                                      > > > >
                                                      > > > > "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                                      > > > > Measure the voltage at R21 hairpin (/PTT-I). This should be
                                                      > ~5
                                                      > > > Vdc.."
                                                      > > > >
                                                      > > > > On my board (with RX switches removed) this voltage is
                                                      ~12V.
                                                      > > > When
                                                      > > > > I've simulated the circuit (in Multisim) it also swings 0
                                                      to
                                                      > > 12V.
                                                      > > > >
                                                      > > > >
                                                      > > > >
                                                      > > > > The collector of Q1 should go to about 12 volts when there
                                                      > is
                                                      > > no
                                                      > > > voltage applied to the PTT IN hole.
                                                      > > > >
                                                      > > > > 73, Dave
                                                      > > > >
                                                      > > > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@>
                                                      > wrote:
                                                      > > > > >
                                                      > > > > > Hi Dave,
                                                      > > > > >
                                                      > > > > > Please check to make sure C30 is not shorted and that D2
                                                      > is
                                                      > > > mounted
                                                      > > > > with the band end of the diode connected to the base of Q1.
                                                      > > > > >
                                                      > > > > > 73,
                                                      > > > > > Tony KB9YIG
                                                      > > > > >
                                                      > > > > > ----- Original Message -----
                                                      > > > > > From: g8xul
                                                      > > > > > To: softrock40@yahoogroups.com
                                                      > > > > > Sent: Saturday, September 27, 2008 4:32 PM
                                                      > > > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                      > > > > >
                                                      > > > > >
                                                      > > > > > Thanks everyone for their helpful comments.
                                                      > > > > >
                                                      > > > > > Made some progress yesterday. I removed R29 and R30 to
                                                      > > isolate
                                                      > > > > the
                                                      > > > > > PTT stage. The S12V line then switched correctly - no
                                                      > > > latching.
                                                      > > > > > The /ptt line also swings 0 to 12V.
                                                      > > > > >
                                                      > > > > > I removed Q7 and Q8 and found Q7 to be duff. About
                                                      600ohms
                                                      > > > > between
                                                      > > > > > each terminal. Q8 seems ok although my testing is a bit
                                                      > > basic.
                                                      > > > S
                                                      > > > > to
                                                      > > > > > D is high resistance until a finger is used to bias the
                                                      > gate
                                                      > > > when
                                                      > > > > it
                                                      > > > > > falls to a few ohms. Plunging the leads into anti static
                                                      > foam
                                                      > > > > resets
                                                      > > > > > it to high impedance.
                                                      > > > > >
                                                      > > > > > Resistances around the connections to Q7/8 on the board
                                                      > > looked
                                                      > > > ok.
                                                      > > > > >
                                                      > > > > > I replaced Q7 with a new device and powered up the board.
                                                      > The
                                                      > > > > > latching problem returned and the new Q7 has lost its
                                                      > magic
                                                      > > > > smoke.
                                                      > > > > > Same 600ohms between terminals.
                                                      > > > > >
                                                      > > > > > I'm going to build the stage in multisim and see if I can
                                                      > try
                                                      > > > out
                                                      > > > > > some faults on that.
                                                      > > > > >
                                                      > > > > > Back to the debug on Monday. Glad I've got the support of
                                                      > a
                                                      > > > great
                                                      > > > > > group.
                                                      > > > > >
                                                      > > > > > 73,
                                                      > > > > >
                                                      > > > > > Dave
                                                      > > > > >
                                                      > > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                      > <singhpk99@>
                                                      > > > wrote:
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > > Please try bypassing C47 and C27 with .1uf and try again
                                                      > > > > > > If you have it happeing in your rxtx, it may be
                                                      > happening
                                                      > > in
                                                      > > > > mine as
                                                      > > > > > > well- will check
                                                      > > > > > >
                                                      > > > > > > 73s
                                                      > > > > > >
                                                      > > > > > > ab2xf
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > >
                                                      > > > > > > --- In softrock40@yahoogroups.com, "Tim O'Rourke"
                                                      > <w4yn@>
                                                      > > > wrote:
                                                      > > > > > > >
                                                      > > > > > > > Be sure that the wiring to serial port is spot on, so
                                                      > > > simple
                                                      > > > > it
                                                      > > > > > may
                                                      > > > > > > > have not been obvious. Do not ask how I know this can
                                                      > > > affect
                                                      > > > > > keying!
                                                      > > > > > > > Tim W4YN
                                                      > > > > > > >
                                                      > > > > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                      > > > <singhpk99@>
                                                      > > > > wrote:
                                                      > > > > > > > >
                                                      > > > > > > > >
                                                      > > > > > > > > It could be oscillating !
                                                      > > > > > > > >
                                                      > > > > > > > > Do you have scope?
                                                      > > > > > > > >
                                                      > > > > > > > > Please check the Q1, Q2 base and collectors using a
                                                      > > > scope.
                                                      > > > > > > > >
                                                      > > > > > > > > 73s
                                                      > > > > > > > > Push
                                                      > > > > > > > > AB2xf
                                                      > > > > > > > >
                                                      > > > > > > > >
                                                      > > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                      > > <dave.james@>
                                                      > > > > wrote:
                                                      > > > > > > > > >
                                                      > > > > > > > > > Q2 tests fine. BC and BE junctions look good,
                                                      > 0.65ish
                                                      > > > > volts
                                                      > > > > > > > > forward
                                                      > > > > > > > > > and high impedance reverse biased. Using the same
                                                      > > > values
                                                      > > > > as
                                                      > > > > > the
                                                      > > > > > > > > > board for R21 and R22 the stage works as expected
                                                      > in
                                                      > > > > > isolation. Q1
                                                      > > > > > > > > > inverter also swings 0v to 12v with ptt. Again,
                                                      > all
                                                      > > > > > resistance
                                                      > > > > > > > > > measurements taken with Q2 out of circuit look
                                                      > right.
                                                      > > > > > > > > >
                                                      > > > > > > > > > Resoldering Q2 into the board the latching
                                                      problem
                                                      > is
                                                      > > > > still
                                                      > > > > > there.
                                                      > > > > > > > > > Next move is to isolate Q1/2 stages by lifting
                                                      R24
                                                      > > and
                                                      > > > > R29.
                                                      > > > > > > > > >
                                                      > > > > > > > > > Any more ideas? Sorry to be a pain but this is
                                                      > > driving
                                                      > > > me
                                                      > > > > > mad!
                                                      > > > > > > > > >
                                                      > > > > > > > > > 73,
                                                      > > > > > > > > > Dave
                                                      > > > > > > > > >
                                                      > > > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                      > > > <dave.james@>
                                                      > > > > > wrote:
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > Thanks Mike,
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > I still haven't resolved the issue. The
                                                      > collector
                                                      > > of
                                                      > > > Q1
                                                      > > > > > waggles
                                                      > > > > > > > > up
                                                      > > > > > > > > > > and down with PTT as expected (except that it
                                                      is
                                                      > > > only
                                                      > > > > 6V
                                                      > > > > > ish when
                                                      > > > > > > > > > PTT
                                                      > > > > > > > > > > is low instead of the ~12 I would expect). I've
                                                      > > > double
                                                      > > > > > checked
                                                      > > > > > > > > > > soldering and component values. All the 'in
                                                      > > circuit'
                                                      > > > > > resistance
                                                      > > > > > > > > > > measurements I've taken look reasonable.
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > I tried shunting R22 with a resistor from the
                                                      > 12V
                                                      > > > line
                                                      > > > > and
                                                      > > > > > found
                                                      > > > > > > > > a
                                                      > > > > > > > > > > value of ~500 ohm would make Q2 unlatch, but it
                                                      > > > latched
                                                      > > > > > again
                                                      > > > > > > > > next
                                                      > > > > > > > > > > time PTT was taken high.
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > I've now pulled Q2 from the circuit and will
                                                      > test
                                                      > > it
                                                      > > > > > tomorrow as
                                                      > > > > > > > > > well
                                                      > > > > > > > > > > as checking the circuit around it with it out
                                                      of
                                                      > > > > circuit.
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > I'll let you know how I get on. I think I'll
                                                      > lash
                                                      > > up
                                                      > > > > the
                                                      > > > > > same
                                                      > > > > > > > > > > circuit on the bench and see what happens! It
                                                      > feels
                                                      > > > a
                                                      > > > > bit
                                                      > > > > > like
                                                      > > > > > > > > > > grasping at straws.
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > Regards,
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > Dave
                                                      > > > > > > > > > >
                                                      > > > > > > > > > > --- In softrock40@yahoogroups.com, "Mike
                                                      > Collins"
                                                      > > > > > <mikecol@>
                                                      > > > > > > > > wrote:
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > > Should S12V not follow PTT? Why does /PTT
                                                      IN
                                                      > > > reduce
                                                      > > > > to
                                                      > > > > > > > > 5V'ish
                                                      > > > > > > > > > > (the
                                                      > > > > > > > > > > > > value given in the detailed contruction
                                                      > notes)?
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > Hi Dave,
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2
                                                      both
                                                      > > act
                                                      > > > as
                                                      > > > > an
                                                      > > > > > > > > > inversion.
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > The only way for /PTT IN to be lower than 12-
                                                      > 0.7V
                                                      > > > is
                                                      > > > > for
                                                      > > > > > Q1 to
                                                      > > > > > > > > be
                                                      > > > > > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE must
                                                      > be
                                                      > > > > > above .6V or
                                                      > > > > > > > > > so. I
                                                      > > > > > > > > > > > would measure across R20 next time it latches
                                                      > up.
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > R20 is used to drain the voltage on the C27
                                                      > > > (at .7V
                                                      > > > > when
                                                      > > > > > Q1 ON)
                                                      > > > > > > > > > down
                                                      > > > > > > > > > > > to help turn off Q1. With no PTTIN voltage
                                                      the
                                                      > > R20
                                                      > > > > > voltage
                                                      > > > > > > > > > should
                                                      > > > > > > > > > > be
                                                      > > > > > > > > > > > at 0 V.
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > Q1 turns on when the PTT IN start going above
                                                      > > 1.2V
                                                      > > > or
                                                      > > > > > so. This
                                                      > > > > > > > > > > > happens when the R19/R20 divider starts to go
                                                      > > > higher
                                                      > > > > > than .6V;
                                                      > > > > > > > > > when
                                                      > > > > > > > > > > > the BE junction starts turning on. When fully
                                                      > on
                                                      > > > Q1
                                                      > > > > > collector
                                                      > > > > > > > > > > should
                                                      > > > > > > > > > > > be at about .2 V or so.
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > Q2 does about the opposite: when /PTTIN goes
                                                      > low;
                                                      > > > the
                                                      > > > > BE
                                                      > > > > > > > > junction
                                                      > > > > > > > > > of
                                                      > > > > > > > > > > > Q2 turns on (at about 12V-0.6V) and then S12V
                                                      > > goes
                                                      > > > > close
                                                      > > > > > to 12V
                                                      > > > > > > > > > > (i.e.
                                                      > > > > > > > > > > > 12V - 0.2V).
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > > > 73, Mike Collins KF4BQ
                                                      > > > > > > > > > > >
                                                      > > > > > > > > > >
                                                      > > > > > > > > >
                                                      > > > > > > > >
                                                      > > > > > > >
                                                      > > > > > >
                                                      > > > > >
                                                      > > > >
                                                      > > >
                                                      > >
                                                      >
                                                    • g8xul
                                                      Hi Push, I ve checked around with a scope. No oscillation on Q1 collector or Q2 S12V. Dave ... Q1 ... there. ... waggles ... when ... checked ... resistance
                                                      Message 26 of 29 , Sep 30, 2008
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                                                        Hi Push,

                                                        I've checked around with a scope. No oscillation on Q1 collector or
                                                        Q2 S12V.

                                                        Dave
                                                        --- In softrock40@yahoogroups.com, "singhpk99" <singhpk99@...> wrote:
                                                        >
                                                        >
                                                        > It could be oscillating !
                                                        >
                                                        > Do you have scope?
                                                        >
                                                        > Please check the Q1, Q2 base and collectors using a scope.
                                                        >
                                                        > 73s
                                                        > Push
                                                        > AB2xf
                                                        >
                                                        >
                                                        > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                                        > >
                                                        > > Q2 tests fine. BC and BE junctions look good, 0.65ish volts
                                                        > forward
                                                        > > and high impedance reverse biased. Using the same values as the
                                                        > > board for R21 and R22 the stage works as expected in isolation.
                                                        Q1
                                                        > > inverter also swings 0v to 12v with ptt. Again, all resistance
                                                        > > measurements taken with Q2 out of circuit look right.
                                                        > >
                                                        > > Resoldering Q2 into the board the latching problem is still
                                                        there.
                                                        > > Next move is to isolate Q1/2 stages by lifting R24 and R29.
                                                        > >
                                                        > > Any more ideas? Sorry to be a pain but this is driving me mad!
                                                        > >
                                                        > > 73,
                                                        > > Dave
                                                        > >
                                                        > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                                        > > >
                                                        > > > Thanks Mike,
                                                        > > >
                                                        > > > I still haven't resolved the issue. The collector of Q1
                                                        waggles
                                                        > up
                                                        > > > and down with PTT as expected (except that it is only 6V ish
                                                        when
                                                        > > PTT
                                                        > > > is low instead of the ~12 I would expect). I've double
                                                        checked
                                                        > > > soldering and component values. All the 'in circuit'
                                                        resistance
                                                        > > > measurements I've taken look reasonable.
                                                        > > >
                                                        > > > I tried shunting R22 with a resistor from the 12V line and
                                                        found
                                                        > a
                                                        > > > value of ~500 ohm would make Q2 unlatch, but it latched again
                                                        > next
                                                        > > > time PTT was taken high.
                                                        > > >
                                                        > > > I've now pulled Q2 from the circuit and will test it tomorrow
                                                        as
                                                        > > well
                                                        > > > as checking the circuit around it with it out of circuit.
                                                        > > >
                                                        > > > I'll let you know how I get on. I think I'll lash up the same
                                                        > > > circuit on the bench and see what happens! It feels a bit
                                                        like
                                                        > > > grasping at straws.
                                                        > > >
                                                        > > > Regards,
                                                        > > >
                                                        > > > Dave
                                                        > > >
                                                        > > > --- In softrock40@yahoogroups.com, "Mike Collins" <mikecol@>
                                                        > wrote:
                                                        > > > >
                                                        > > > >
                                                        > > > > > Should S12V not follow PTT? Why does /PTT IN reduce to
                                                        > 5V'ish
                                                        > > > (the
                                                        > > > > > value given in the detailed contruction notes)?
                                                        > > > >
                                                        > > > > Hi Dave,
                                                        > > > >
                                                        > > > > Yes, S12V should follow PTT IN. Q1 and Q2 both act as an
                                                        > > inversion.
                                                        > > > >
                                                        > > > > The only way for /PTT IN to be lower than 12-0.7V is for Q1
                                                        to
                                                        > be
                                                        > > > > somewhat ON. For Q1 to be on: the Q1 BE must be above .6V
                                                        or
                                                        > > so. I
                                                        > > > > would measure across R20 next time it latches up.
                                                        > > > >
                                                        > > > > R20 is used to drain the voltage on the C27 (at .7V when Q1
                                                        ON)
                                                        > > down
                                                        > > > > to help turn off Q1. With no PTTIN voltage the R20 voltage
                                                        > > should
                                                        > > > be
                                                        > > > > at 0 V.
                                                        > > > >
                                                        > > > > Q1 turns on when the PTT IN start going above 1.2V or so.
                                                        This
                                                        > > > > happens when the R19/R20 divider starts to go higher
                                                        than .6V;
                                                        > > when
                                                        > > > > the BE junction starts turning on. When fully on Q1
                                                        collector
                                                        > > > should
                                                        > > > > be at about .2 V or so.
                                                        > > > >
                                                        > > > > Q2 does about the opposite: when /PTTIN goes low; the BE
                                                        > junction
                                                        > > of
                                                        > > > > Q2 turns on (at about 12V-0.6V) and then S12V goes close to
                                                        12V
                                                        > > > (i.e.
                                                        > > > > 12V - 0.2V).
                                                        > > > >
                                                        > > > > 73, Mike Collins KF4BQ
                                                        > > > >
                                                        > > >
                                                        > >
                                                        >
                                                      • g8xul
                                                        Tim, I ve got the board connected to the D type but not connected to the computer as yet. I m connecting the ppt_in pad on the board to D2 cathode as in the
                                                        Message 27 of 29 , Sep 30, 2008
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                                                          Tim,
                                                          I've got the board connected to the D type but not connected to the
                                                          computer as yet. I'm connecting the ppt_in pad on the board to D2
                                                          cathode as in the construction notes. I have tried connecting
                                                          ptt_in to grnd for the 0V condition instead of leaving it floating
                                                          as in the notes. This makes no difference.

                                                          Thanks for your support.
                                                          73, Dave

                                                          --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@...> wrote:
                                                          >
                                                          > Not sure about testing with BPF out will need to ponder that. It
                                                          was
                                                          > just a random thouht. I assume you are testing with serial cable
                                                          > connected to PC. Double check wiring to db9 I had one wire
                                                          reversed
                                                          > and it drove me crazy for a day troubleshooting the PPT as you are.
                                                          > Tim
                                                          > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                                          > >
                                                          > > Hi Tim,
                                                          > >
                                                          > > I've been testing without the RxBPF installed. Could this be
                                                          the
                                                          > > problem? I guess the BPF provides a transient route to earth
                                                          for
                                                          > > the source of Q7.
                                                          > >
                                                          > > The main board has a short length of hookup coax connected to
                                                          the
                                                          > > Ant pads and this is not short inner to outer.
                                                          > >
                                                          > > 73, Dave
                                                          > >
                                                          > > --- In softrock40@yahoogroups.com, "Tim O'Rourke" <w4yn@> wrote:
                                                          > > >
                                                          > > > Do you have the antenna connected when Q7 goes south? If so ck
                                                          > > that
                                                          > > > the connections for antenna on PCB are not reversed>
                                                          > > > Tim W4YN
                                                          > > > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                                          > > > >
                                                          > > > > Tony,
                                                          > > > >
                                                          > > > > Checked C30 is not shorted. D2 has its band at the top
                                                          (base
                                                          > > Q1).
                                                          > > > >
                                                          > > > > With Q7 / Q8 removed and the board powered I measured
                                                          > > > >
                                                          > > > > with ptt in = 0V
                                                          > > > > /ptt in = 11.57V
                                                          > > > > S12V = 0V
                                                          > > > > Q7 gate pad = 11.57V
                                                          > > > > Q7 drain pad = 0V
                                                          > > > > Q7 source pad = 0V
                                                          > > > > Q8 gate pad = 0V
                                                          > > > > Q8 drain pad = 0V
                                                          > > > > Q8 source pad = 0V
                                                          > > > >
                                                          > > > > with ptt in = 12V
                                                          > > > > /ptt in = 0.046V
                                                          > > > > S12V = 11.47V
                                                          > > > > Q7 gate pad = 0.047
                                                          > > > > Q7 drain pad = 0V
                                                          > > > > Q7 source pad = 0V
                                                          > > > > Q8 gate pad = 11.47V
                                                          > > > > Q8 drain pad = 0V
                                                          > > > > Q8 source pad = 0V
                                                          > > > >
                                                          > > > > Soldered in 2 new BS170 (robbed from the 160m PA kit). S12V
                                                          is
                                                          > > now
                                                          > > > > stuck high. Removed R29/30 and in circuit resistance checks
                                                          > > > suggest
                                                          > > > > Q7 has blown again.
                                                          > > > >
                                                          > > > > I'm stumped as to what to try next.
                                                          > > > >
                                                          > > > > 73, Dave
                                                          > > > > --- In softrock40@yahoogroups.com, "Tony Parks" <kb9yig@>
                                                          wrote:
                                                          > > > > >
                                                          > > > > > Hi Dave,
                                                          > > > > >
                                                          > > > > > I will add comments below. I was trying to think what
                                                          might
                                                          > > > cause
                                                          > > > > Q7 to fail and looking for the possibility of high current
                                                          > > through
                                                          > > > > Q7 where both Q7 and Q8 were on at the same time.
                                                          > > > > >
                                                          > > > > > Sorry the v6.3 has been a problem.
                                                          > > > > >
                                                          > > > > > 73,
                                                          > > > > > Tony KB9YIG
                                                          > > > > >
                                                          > > > > > ----- Original Message -----
                                                          > > > > > From: g8xul
                                                          > > > > > To: softrock40@yahoogroups.com
                                                          > > > > > Sent: Sunday, September 28, 2008 2:20 PM
                                                          > > > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                          > > > > >
                                                          > > > > >
                                                          > > > > > Thanks for reply Tony,
                                                          > > > > >
                                                          > > > > > I haven't got the board with me but:
                                                          > > > > >
                                                          > > > > > "Please check to make sure C30 is not shorted"
                                                          > > > > > I'll check tomorrow but I haven't got the PA daughter
                                                          board
                                                          > > > > installed
                                                          > > > > > so C30 only goes to the J2 pin 5 (open circuit).
                                                          > > > > >
                                                          > > > > > Ok..
                                                          > > > > >
                                                          > > > > > "D2 is mounted with the band end of the diode connected
                                                          to
                                                          > > the
                                                          > > > > base
                                                          > > > > > of Q1."
                                                          > > > > >
                                                          > > > > > I've checked this (but will check again) however the
                                                          > > collector
                                                          > > > > of Q1
                                                          > > > > > swings 0 to 12 V with the RX switches removed. I'm a bit
                                                          > > > > confused by
                                                          > > > > > the test in the detailed build notes...
                                                          > > > > >
                                                          > > > > > "Unclip the lead at the D1 cathode (this sets PTT OFF)
                                                          > > > > > Measure the voltage at R21 hairpin (/PTT-I). This should
                                                          be
                                                          > > ~5
                                                          > > > > Vdc.."
                                                          > > > > >
                                                          > > > > > On my board (with RX switches removed) this voltage is
                                                          > ~12V.
                                                          > > > > When
                                                          > > > > > I've simulated the circuit (in Multisim) it also swings
                                                          0
                                                          > to
                                                          > > > 12V.
                                                          > > > > >
                                                          > > > > >
                                                          > > > > >
                                                          > > > > > The collector of Q1 should go to about 12 volts when
                                                          there
                                                          > > is
                                                          > > > no
                                                          > > > > voltage applied to the PTT IN hole.
                                                          > > > > >
                                                          > > > > > 73, Dave
                                                          > > > > >
                                                          > > > > > --- In softrock40@yahoogroups.com, "Tony Parks"
                                                          <kb9yig@>
                                                          > > wrote:
                                                          > > > > > >
                                                          > > > > > > Hi Dave,
                                                          > > > > > >
                                                          > > > > > > Please check to make sure C30 is not shorted and that
                                                          D2
                                                          > > is
                                                          > > > > mounted
                                                          > > > > > with the band end of the diode connected to the base of
                                                          Q1.
                                                          > > > > > >
                                                          > > > > > > 73,
                                                          > > > > > > Tony KB9YIG
                                                          > > > > > >
                                                          > > > > > > ----- Original Message -----
                                                          > > > > > > From: g8xul
                                                          > > > > > > To: softrock40@yahoogroups.com
                                                          > > > > > > Sent: Saturday, September 27, 2008 4:32 PM
                                                          > > > > > > Subject: [softrock40] Re: Troubleshooting RXTX 6.3
                                                          > > > > > >
                                                          > > > > > >
                                                          > > > > > > Thanks everyone for their helpful comments.
                                                          > > > > > >
                                                          > > > > > > Made some progress yesterday. I removed R29 and R30 to
                                                          > > > isolate
                                                          > > > > > the
                                                          > > > > > > PTT stage. The S12V line then switched correctly - no
                                                          > > > > latching.
                                                          > > > > > > The /ptt line also swings 0 to 12V.
                                                          > > > > > >
                                                          > > > > > > I removed Q7 and Q8 and found Q7 to be duff. About
                                                          > 600ohms
                                                          > > > > > between
                                                          > > > > > > each terminal. Q8 seems ok although my testing is a
                                                          bit
                                                          > > > basic.
                                                          > > > > S
                                                          > > > > > to
                                                          > > > > > > D is high resistance until a finger is used to bias
                                                          the
                                                          > > gate
                                                          > > > > when
                                                          > > > > > it
                                                          > > > > > > falls to a few ohms. Plunging the leads into anti
                                                          static
                                                          > > foam
                                                          > > > > > resets
                                                          > > > > > > it to high impedance.
                                                          > > > > > >
                                                          > > > > > > Resistances around the connections to Q7/8 on the
                                                          board
                                                          > > > looked
                                                          > > > > ok.
                                                          > > > > > >
                                                          > > > > > > I replaced Q7 with a new device and powered up the
                                                          board.
                                                          > > The
                                                          > > > > > > latching problem returned and the new Q7 has lost its
                                                          > > magic
                                                          > > > > > smoke.
                                                          > > > > > > Same 600ohms between terminals.
                                                          > > > > > >
                                                          > > > > > > I'm going to build the stage in multisim and see if I
                                                          can
                                                          > > try
                                                          > > > > out
                                                          > > > > > > some faults on that.
                                                          > > > > > >
                                                          > > > > > > Back to the debug on Monday. Glad I've got the support
                                                          of
                                                          > > a
                                                          > > > > great
                                                          > > > > > > group.
                                                          > > > > > >
                                                          > > > > > > 73,
                                                          > > > > > >
                                                          > > > > > > Dave
                                                          > > > > > >
                                                          > > > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                          > > <singhpk99@>
                                                          > > > > wrote:
                                                          > > > > > > >
                                                          > > > > > > >
                                                          > > > > > > > Please try bypassing C47 and C27 with .1uf and try
                                                          again
                                                          > > > > > > > If you have it happeing in your rxtx, it may be
                                                          > > happening
                                                          > > > in
                                                          > > > > > mine as
                                                          > > > > > > > well- will check
                                                          > > > > > > >
                                                          > > > > > > > 73s
                                                          > > > > > > >
                                                          > > > > > > > ab2xf
                                                          > > > > > > >
                                                          > > > > > > >
                                                          > > > > > > >
                                                          > > > > > > >
                                                          > > > > > > > --- In softrock40@yahoogroups.com, "Tim O'Rourke"
                                                          > > <w4yn@>
                                                          > > > > wrote:
                                                          > > > > > > > >
                                                          > > > > > > > > Be sure that the wiring to serial port is spot on,
                                                          so
                                                          > > > > simple
                                                          > > > > > it
                                                          > > > > > > may
                                                          > > > > > > > > have not been obvious. Do not ask how I know this
                                                          can
                                                          > > > > affect
                                                          > > > > > > keying!
                                                          > > > > > > > > Tim W4YN
                                                          > > > > > > > >
                                                          > > > > > > > > --- In softrock40@yahoogroups.com, "singhpk99"
                                                          > > > > <singhpk99@>
                                                          > > > > > wrote:
                                                          > > > > > > > > >
                                                          > > > > > > > > >
                                                          > > > > > > > > > It could be oscillating !
                                                          > > > > > > > > >
                                                          > > > > > > > > > Do you have scope?
                                                          > > > > > > > > >
                                                          > > > > > > > > > Please check the Q1, Q2 base and collectors
                                                          using a
                                                          > > > > scope.
                                                          > > > > > > > > >
                                                          > > > > > > > > > 73s
                                                          > > > > > > > > > Push
                                                          > > > > > > > > > AB2xf
                                                          > > > > > > > > >
                                                          > > > > > > > > >
                                                          > > > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                          > > > <dave.james@>
                                                          > > > > > wrote:
                                                          > > > > > > > > > >
                                                          > > > > > > > > > > Q2 tests fine. BC and BE junctions look good,
                                                          > > 0.65ish
                                                          > > > > > volts
                                                          > > > > > > > > > forward
                                                          > > > > > > > > > > and high impedance reverse biased. Using the
                                                          same
                                                          > > > > values
                                                          > > > > > as
                                                          > > > > > > the
                                                          > > > > > > > > > > board for R21 and R22 the stage works as
                                                          expected
                                                          > > in
                                                          > > > > > > isolation. Q1
                                                          > > > > > > > > > > inverter also swings 0v to 12v with ptt.
                                                          Again,
                                                          > > all
                                                          > > > > > > resistance
                                                          > > > > > > > > > > measurements taken with Q2 out of circuit look
                                                          > > right.
                                                          > > > > > > > > > >
                                                          > > > > > > > > > > Resoldering Q2 into the board the latching
                                                          > problem
                                                          > > is
                                                          > > > > > still
                                                          > > > > > > there.
                                                          > > > > > > > > > > Next move is to isolate Q1/2 stages by lifting
                                                          > R24
                                                          > > > and
                                                          > > > > > R29.
                                                          > > > > > > > > > >
                                                          > > > > > > > > > > Any more ideas? Sorry to be a pain but this is
                                                          > > > driving
                                                          > > > > me
                                                          > > > > > > mad!
                                                          > > > > > > > > > >
                                                          > > > > > > > > > > 73,
                                                          > > > > > > > > > > Dave
                                                          > > > > > > > > > >
                                                          > > > > > > > > > > --- In softrock40@yahoogroups.com, "g8xul"
                                                          > > > > <dave.james@>
                                                          > > > > > > wrote:
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > Thanks Mike,
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > I still haven't resolved the issue. The
                                                          > > collector
                                                          > > > of
                                                          > > > > Q1
                                                          > > > > > > waggles
                                                          > > > > > > > > > up
                                                          > > > > > > > > > > > and down with PTT as expected (except that
                                                          it
                                                          > is
                                                          > > > > only
                                                          > > > > > 6V
                                                          > > > > > > ish when
                                                          > > > > > > > > > > PTT
                                                          > > > > > > > > > > > is low instead of the ~12 I would expect).
                                                          I've
                                                          > > > > double
                                                          > > > > > > checked
                                                          > > > > > > > > > > > soldering and component values. All the 'in
                                                          > > > circuit'
                                                          > > > > > > resistance
                                                          > > > > > > > > > > > measurements I've taken look reasonable.
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > I tried shunting R22 with a resistor from
                                                          the
                                                          > > 12V
                                                          > > > > line
                                                          > > > > > and
                                                          > > > > > > found
                                                          > > > > > > > > > a
                                                          > > > > > > > > > > > value of ~500 ohm would make Q2 unlatch, but
                                                          it
                                                          > > > > latched
                                                          > > > > > > again
                                                          > > > > > > > > > next
                                                          > > > > > > > > > > > time PTT was taken high.
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > I've now pulled Q2 from the circuit and will
                                                          > > test
                                                          > > > it
                                                          > > > > > > tomorrow as
                                                          > > > > > > > > > > well
                                                          > > > > > > > > > > > as checking the circuit around it with it
                                                          out
                                                          > of
                                                          > > > > > circuit.
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > I'll let you know how I get on. I think I'll
                                                          > > lash
                                                          > > > up
                                                          > > > > > the
                                                          > > > > > > same
                                                          > > > > > > > > > > > circuit on the bench and see what happens!
                                                          It
                                                          > > feels
                                                          > > > > a
                                                          > > > > > bit
                                                          > > > > > > like
                                                          > > > > > > > > > > > grasping at straws.
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > Regards,
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > Dave
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > > > --- In softrock40@yahoogroups.com, "Mike
                                                          > > Collins"
                                                          > > > > > > <mikecol@>
                                                          > > > > > > > > > wrote:
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > > Should S12V not follow PTT? Why
                                                          does /PTT
                                                          > IN
                                                          > > > > reduce
                                                          > > > > > to
                                                          > > > > > > > > > 5V'ish
                                                          > > > > > > > > > > > (the
                                                          > > > > > > > > > > > > > value given in the detailed contruction
                                                          > > notes)?
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > Hi Dave,
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > Yes, S12V should follow PTT IN. Q1 and Q2
                                                          > both
                                                          > > > act
                                                          > > > > as
                                                          > > > > > an
                                                          > > > > > > > > > > inversion.
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > The only way for /PTT IN to be lower than
                                                          12-
                                                          > > 0.7V
                                                          > > > > is
                                                          > > > > > for
                                                          > > > > > > Q1 to
                                                          > > > > > > > > > be
                                                          > > > > > > > > > > > > somewhat ON. For Q1 to be on: the Q1 BE
                                                          must
                                                          > > be
                                                          > > > > > > above .6V or
                                                          > > > > > > > > > > so. I
                                                          > > > > > > > > > > > > would measure across R20 next time it
                                                          latches
                                                          > > up.
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > R20 is used to drain the voltage on the
                                                          C27
                                                          > > > > (at .7V
                                                          > > > > > when
                                                          > > > > > > Q1 ON)
                                                          > > > > > > > > > > down
                                                          > > > > > > > > > > > > to help turn off Q1. With no PTTIN voltage
                                                          > the
                                                          > > > R20
                                                          > > > > > > voltage
                                                          > > > > > > > > > > should
                                                          > > > > > > > > > > > be
                                                          > > > > > > > > > > > > at 0 V.
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > Q1 turns on when the PTT IN start going
                                                          above
                                                          > > > 1.2V
                                                          > > > > or
                                                          > > > > > > so. This
                                                          > > > > > > > > > > > > happens when the R19/R20 divider starts to
                                                          go
                                                          > > > > higher
                                                          > > > > > > than .6V;
                                                          > > > > > > > > > > when
                                                          > > > > > > > > > > > > the BE junction starts turning on. When
                                                          fully
                                                          > > on
                                                          > > > > Q1
                                                          > > > > > > collector
                                                          > > > > > > > > > > > should
                                                          > > > > > > > > > > > > be at about .2 V or so.
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > Q2 does about the opposite: when /PTTIN
                                                          goes
                                                          > > low;
                                                          > > > > the
                                                          > > > > > BE
                                                          > > > > > > > > > junction
                                                          > > > > > > > > > > of
                                                          > > > > > > > > > > > > Q2 turns on (at about 12V-0.6V) and then
                                                          S12V
                                                          > > > goes
                                                          > > > > > close
                                                          > > > > > > to 12V
                                                          > > > > > > > > > > > (i.e.
                                                          > > > > > > > > > > > > 12V - 0.2V).
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > > > 73, Mike Collins KF4BQ
                                                          > > > > > > > > > > > >
                                                          > > > > > > > > > > >
                                                          > > > > > > > > > >
                                                          > > > > > > > > >
                                                          > > > > > > > >
                                                          > > > > > > >
                                                          > > > > > >
                                                          > > > > >
                                                          > > > >
                                                          > > >
                                                          > >
                                                          >
                                                        • g8xul
                                                          Dear All, Thanks to everyone that s helped with this. The good news is that I can at last put this (long) thread to bed, and start getting some sleep. The
                                                          Message 28 of 29 , Oct 1, 2008
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                                                            Dear All,

                                                            Thanks to everyone that's helped with this. The good news is that I
                                                            can at last put this (long) thread to bed, and start getting some
                                                            sleep. The bad news is I'm not sure of the solution. I tried 3
                                                            things:

                                                            1. Used a BS170 from a different source. (sorry Tony - no slur
                                                            intended, just an observation:-)
                                                            2. I tested with the RX BPF installed.
                                                            3. I wrapped the legs of the Q7 FET together with wire before
                                                            installing it to absolutly rule out an ESD problem.(Are these devices
                                                            really a problem? To kill Q7 3 out of 3 times whilst Q8 survives is
                                                            some chance.)

                                                            Anyway - PTT and RX switching now work as expected.

                                                            I'd be interested on any comments as to running the board without
                                                            RXBPF. I won't be doing it till I learn better.

                                                            Phew.

                                                            73,Dave, G8XUL


                                                            --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
                                                            >
                                                            > I'm having trouble with the simplest element of the RXTX6.3
                                                            > transmitter section and would appreciate some help before I start
                                                            > pulling out components.
                                                            >
                                                            > The RX seems to work fine. I've checked soldering and component
                                                            > values under magnification. I used good ESD practice throughout
                                                            > construction.
                                                            >
                                                            > The problem is with the PTT section. Construction of the main
                                                            board
                                                            > is complete and I'm testing without the PA daughter board
                                                            installed.
                                                            > My original problem was that when testing the PA module The current
                                                            > draw exceeded my 150mA current limit, knocking the supply voltage
                                                            > down to a couple of volts. I decided to check the voltages at J1 /
                                                            > J2 before faulting the PA board.
                                                            >
                                                            > On power up the current draw is ~95mA @ 7.047 center frequency.
                                                            With
                                                            > a DMM I measure:
                                                            >
                                                            > PTT IN 0V
                                                            > /PTT IN ~10.5V
                                                            > S12V 0V
                                                            >
                                                            > PTT IN was then connected to 12V (Cathode D1). Readings now:
                                                            >
                                                            > /PTT IN 0V
                                                            > S12V ~11.8V
                                                            >
                                                            > PTT IN back to 0V (connected to ground). Readings now:
                                                            >
                                                            > /PTT IN ~ 5.8V
                                                            > S12V ~11.8V
                                                            >
                                                            > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
                                                            > indefinately - irrespective of changes to PTT untill the power is
                                                            > removed. The readings above can then be reproduced.
                                                            >
                                                            > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish (the
                                                            > value given in the detailed contruction notes)?
                                                            >
                                                            > Any help much appreciated.
                                                            >
                                                            > 73, Dave
                                                            >
                                                          • singhpk99
                                                            hi Dave, Please wire a zener between the Gate and source on the bs170s to prevent further burnups. zener voltage should be 12 volts 400mw 73s push ab2xf
                                                            Message 29 of 29 , Oct 1, 2008
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                                                              hi Dave,

                                                              Please wire a zener between the Gate and source on the bs170s
                                                              to prevent further burnups.

                                                              zener voltage should be 12 volts 400mw

                                                              73s
                                                              push
                                                              ab2xf

                                                              --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
                                                              >
                                                              > Dear All,
                                                              >
                                                              > Thanks to everyone that's helped with this. The good news is that I
                                                              > can at last put this (long) thread to bed, and start getting some
                                                              > sleep. The bad news is I'm not sure of the solution. I tried 3
                                                              > things:
                                                              >
                                                              > 1. Used a BS170 from a different source. (sorry Tony - no slur
                                                              > intended, just an observation:-)
                                                              > 2. I tested with the RX BPF installed.
                                                              > 3. I wrapped the legs of the Q7 FET together with wire before
                                                              > installing it to absolutly rule out an ESD problem.(Are these devices
                                                              > really a problem? To kill Q7 3 out of 3 times whilst Q8 survives is
                                                              > some chance.)
                                                              >
                                                              > Anyway - PTT and RX switching now work as expected.
                                                              >
                                                              > I'd be interested on any comments as to running the board without
                                                              > RXBPF. I won't be doing it till I learn better.
                                                              >
                                                              > Phew.
                                                              >
                                                              > 73,Dave, G8XUL
                                                              >
                                                              >
                                                              > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
                                                              > >
                                                              > > I'm having trouble with the simplest element of the RXTX6.3
                                                              > > transmitter section and would appreciate some help before I start
                                                              > > pulling out components.
                                                              > >
                                                              > > The RX seems to work fine. I've checked soldering and component
                                                              > > values under magnification. I used good ESD practice throughout
                                                              > > construction.
                                                              > >
                                                              > > The problem is with the PTT section. Construction of the main
                                                              > board
                                                              > > is complete and I'm testing without the PA daughter board
                                                              > installed.
                                                              > > My original problem was that when testing the PA module The current
                                                              > > draw exceeded my 150mA current limit, knocking the supply voltage
                                                              > > down to a couple of volts. I decided to check the voltages at J1 /
                                                              > > J2 before faulting the PA board.
                                                              > >
                                                              > > On power up the current draw is ~95mA @ 7.047 center frequency.
                                                              > With
                                                              > > a DMM I measure:
                                                              > >
                                                              > > PTT IN 0V
                                                              > > /PTT IN ~10.5V
                                                              > > S12V 0V
                                                              > >
                                                              > > PTT IN was then connected to 12V (Cathode D1). Readings now:
                                                              > >
                                                              > > /PTT IN 0V
                                                              > > S12V ~11.8V
                                                              > >
                                                              > > PTT IN back to 0V (connected to ground). Readings now:
                                                              > >
                                                              > > /PTT IN ~ 5.8V
                                                              > > S12V ~11.8V
                                                              > >
                                                              > > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
                                                              > > indefinately - irrespective of changes to PTT untill the power is
                                                              > > removed. The readings above can then be reproduced.
                                                              > >
                                                              > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish (the
                                                              > > value given in the detailed contruction notes)?
                                                              > >
                                                              > > Any help much appreciated.
                                                              > >
                                                              > > 73, Dave
                                                              > >
                                                              >
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