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Re: [softrock40] RXTX ensemble help

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  • Alan
    ... From: jamesdee3721 Subject: [softrock40] RXTX ensemble help ... Check all components, connections and solder splashes around Q4. If nothing found measure
    Message 1 of 14 , Mar 2, 2011
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      ----- Original Message -----
      From: "jamesdee3721"
      Subject: [softrock40] RXTX ensemble help



      > My board draws 300mA when PTT is active, which is double what it should.
      > With PTT off the draw is within normal range (28mA) and all of the other
      > values I have checked have been as well. My power supply is showing 15v
      > but I assume that this isn't the issue.
      >

      Check all components, connections and solder splashes around Q4. If nothing
      found measure all voltages around this and as before with 12V power so we
      can compare with Robby's measurements

      73 Alan G4ZFQ
    • JOHN GREUSEL
      James, Is it possible you re loading down a weak switching PS beyond what s it s capable of? - amps up voltage down? John KC9OJV ... From: jamesdee3721
      Message 2 of 14 , Mar 2, 2011
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        James,

        Is it possible you're loading down a weak switching PS beyond what's it's capable of?
        - amps up voltage down?

        John
        KC9OJV

        --- On Wed, 3/2/11, jamesdee3721 <xvf@...> wrote:

        From: jamesdee3721 <xvf@...>
        Subject: [softrock40] RXTX ensemble help
        To: softrock40@yahoogroups.com
        Date: Wednesday, March 2, 2011, 12:57 PM

         

        I'm not very computer savvy but here goes nothing.

        I have been assembling the RXTX for my father's 80th and can't seem to get things to sit right on the TX side.

        My board draws 300mA when PTT is active, which is double what it should. With PTT off the draw is within normal range (28mA) and all of the other values I have checked have been as well. My power supply is showing 15v but I assume that this isn't the issue.

        My other test values with PTT ON are as follows

        R35 hairpin 7.11V
        across R48 196mV
        across R49 206mv
        R46 hairpin 3.01V

        Something seems to be quite off, I have double checked the resistors, as well as T3/T4 conductivity and can't seem to locate the issue. I've also replaced Q3/Q5/Q7/Q8 without any luck.

        Any help would be greatly appreciated,
        James

      • Alan
        ... From: JOHN GREUSEL Subject: Re: [softrock40] RXTX ensemble help ... - amps up voltage down? Why is R46 hairpin voltage high? 73 Alan G4ZFQ
        Message 3 of 14 , Mar 2, 2011
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          ----- Original Message -----
          From: "JOHN GREUSEL"
          Subject: Re: [softrock40] RXTX ensemble help



          >Is it possible you're loading down a weak switching PS beyond what's it's
          >capable of?
          - amps up voltage down?


          Why is R46 hairpin voltage high?

          73 Alan G4ZFQ
        • jamesdee3721
          I actually miswrote the voltage15 instead of 13 It s 13.02V for the power supply which I am seeing on the emitter for q3.
          Message 4 of 14 , Mar 2, 2011
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            I actually miswrote the voltage15 instead of 13
            It's 13.02V for the power supply which I am seeing on the emitter for q3.


            --- In softrock40@yahoogroups.com, "KF4BQ" <mikecol@...> wrote:
            >
            >
            > > My other test values with PTT ON are as follows
            > >
            > > R35 hairpin 7.11V
            > > across R48 196mV
            > > across R49 206mv
            > > R46 hairpin 3.01V
            >
            > Hi James,
            >
            > The R35 hairpin should be S12v (i.e. Switched 12V). This should be very close to the input 12VDC (within 200-500mV). Q3 acts as a switch passing the 12VDC thru when /PTT goes low.
            >
            > Your 7.11V reading is very low, and this gives a big drop across the E-C of Q3. Measure voltage on Emitter of Q3 to make sure the 12VDC (your 15V is getting there). When /PTT is low the B-E of Q3 should be .7V and the E-C should be .2V.
            >
            > The S12v feeds the PA driver and PA bias so must be correct.
            >
            > Not sure where you are getting the high current. Touch everything and see if something is getting ready to blow !!
            >
            > 73, Mike Collins KF4BQ
            >
          • JOHN GREUSEL
            How many watts are you consuming at 7.1 volts? John KC9OJV ... From: jamesdee3721 Subject: [softrock40] Re: RXTX ensemble help To:
            Message 5 of 14 , Mar 2, 2011
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              How many watts are you consuming at 7.1 volts?

              John
              KC9OJV

              --- On Wed, 3/2/11, jamesdee3721 <xvf@...> wrote:

              From: jamesdee3721 <xvf@...>
              Subject: [softrock40] Re: RXTX ensemble help
              To: softrock40@yahoogroups.com
              Date: Wednesday, March 2, 2011, 3:40 PM

               

              I actually miswrote the voltage15 instead of 13
              It's 13.02V for the power supply which I am seeing on the emitter for q3.

              --- In softrock40@yahoogroups.com, "KF4BQ" <mikecol@...> wrote:
              >
              >
              > > My other test values with PTT ON are as follows
              > >
              > > R35 hairpin 7.11V
              > > across R48 196mV
              > > across R49 206mv
              > > R46 hairpin 3.01V
              >
              > Hi James,
              >
              > The R35 hairpin should be S12v (i.e. Switched 12V). This should be very close to the input 12VDC (within 200-500mV). Q3 acts as a switch passing the 12VDC thru when /PTT goes low.
              >
              > Your 7.11V reading is very low, and this gives a big drop across the E-C of Q3. Measure voltage on Emitter of Q3 to make sure the 12VDC (your 15V is getting there). When /PTT is low the B-E of Q3 should be .7V and the E-C should be .2V.
              >
              > The S12v feeds the PA driver and PA bias so must be correct.
              >
              > Not sure where you are getting the high current. Touch everything and see if something is getting ready to blow !!
              >
              > 73, Mike Collins KF4BQ
              >

            • jamesdee3721
              No splashes or bridges near Q4, I ve checked the resistors and they are all a match. With PTT active: R35 hairpin 6.94v R37 hairpin 3.74v R39 hairpin 3.45v R46
              Message 6 of 14 , Mar 2, 2011
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                No splashes or bridges near Q4, I've checked the resistors and they are all a match.

                With PTT active:

                R35 hairpin 6.94v
                R37 hairpin 3.74v
                R39 hairpin 3.45v
                R46 hairpin 2.98v

                Across R49 165mv
                Across R48 152mv

                Q3 is getting 13.1v

                --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                >
                >
                > ----- Original Message -----
                > From: "jamesdee3721"
                > Subject: [softrock40] RXTX ensemble help
                >
                >
                >
                > > My board draws 300mA when PTT is active, which is double what it should.
                > > With PTT off the draw is within normal range (28mA) and all of the other
                > > values I have checked have been as well. My power supply is showing 15v
                > > but I assume that this isn't the issue.
                > >
                >
                > Check all components, connections and solder splashes around Q4. If nothing
                > found measure all voltages around this and as before with 12V power so we
                > can compare with Robby's measurements
                >
                > 73 Alan G4ZFQ
                >
              • Alan
                ... Subject: [softrock40] Re: RXTX ensemble help ... This is puzzling, as Mike said at R35 we expect about 12V. Does Q3 have 13.1v in the fault condition? yes
                Message 7 of 14 , Mar 3, 2011
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                  ----- Original Message -----

                  Subject: [softrock40] Re: RXTX ensemble help


                  > No splashes or bridges near Q4, I've checked the resistors and they are
                  > all a match.
                  >
                  > With PTT active:
                  >
                  > R35 hairpin 6.94v
                  > R37 hairpin 3.74v
                  > R39 hairpin 3.45v
                  > R46 hairpin 2.98v
                  >
                  > Across R49 165mv
                  > Across R48 152mv
                  >
                  > Q3 is getting 13.1v
                  >


                  This is puzzling, as Mike said at R35 we expect about 12V.

                  Does Q3 have 13.1v in the fault condition? yes you say. It should be able to
                  supply the fault current with no significant drop. Measure voltages on Q3.

                  There are two sets of faulty readings.

                  1) The voltage at R37 shows a current of 190mA if your R35 (S12v) voltage
                  reading is correct.
                  Check Q6, that it is a 2N2222, the correct orientation, no bad joints or
                  whiskers. Check voltages on it's pins.

                  2) The voltages on R 48, 49, 46 indicate the output is biased too high and
                  drawing SOME (~70mA?) of the excess current. These high voltages should be
                  coming from S12v at R35 which you measure low. Measure voltages at Q5 and
                  Q4.
                  I suppose the low S12v may cause this but I can't see why. A low supply
                  would normally mean everything supplied by it would be low.

                  The common thing between these two is T3. But the voltages you give do not
                  seem to make incorrect wiring of this this a suspect.


                  73 Alan G4ZFQ
                • jamesdee3721
                  It turned out that Q4 was bad and was shorting to ground, replaced it and that obviously helped the bias/voltage issues. The problem now is that while the RF
                  Message 8 of 14 , Mar 6, 2011
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                    It turned out that Q4 was bad and was shorting to ground, replaced it and that obviously helped the bias/voltage issues.

                    The problem now is that while the RF output scales with the Rocky I/Q amplitude it tops out at 0.25v sadly measured at the norcal load.

                    Updated measurements are more in line with the builders notes, I've checked the TX opamp voltages and they are all in line. The soundcard feed it also correct.

                    R35 hairpin 12.84v
                    R46 hairpin 2.68v
                    Across R49 72mv
                    Across R48 67mv

                    Not sure how to go about finding the RF power fault, continuity tests have not come up with any obvious issues. Any test points you could recommend to try and track down the issue would be appreciated. Not sure if I should replace the PA/driver BS170's.

                    I'd just like to thank everyone for the helpful messages, it's been a few decades since I've done this sort of thing and it's slow coming back to me.



                    --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                    >
                    >
                    > ----- Original Message -----
                    >
                    > Subject: [softrock40] Re: RXTX ensemble help
                    >
                    >
                    > > No splashes or bridges near Q4, I've checked the resistors and they are
                    > > all a match.
                    > >
                    > > With PTT active:
                    > >
                    > > R35 hairpin 6.94v
                    > > R37 hairpin 3.74v
                    > > R39 hairpin 3.45v
                    > > R46 hairpin 2.98v
                    > >
                    > > Across R49 165mv
                    > > Across R48 152mv
                    > >
                    > > Q3 is getting 13.1v
                    > >
                    >
                    >
                    > This is puzzling, as Mike said at R35 we expect about 12V.
                    >
                    > Does Q3 have 13.1v in the fault condition? yes you say. It should be able to
                    > supply the fault current with no significant drop. Measure voltages on Q3.
                    >
                    > There are two sets of faulty readings.
                    >
                    > 1) The voltage at R37 shows a current of 190mA if your R35 (S12v) voltage
                    > reading is correct.
                    > Check Q6, that it is a 2N2222, the correct orientation, no bad joints or
                    > whiskers. Check voltages on it's pins.
                    >
                    > 2) The voltages on R 48, 49, 46 indicate the output is biased too high and
                    > drawing SOME (~70mA?) of the excess current. These high voltages should be
                    > coming from S12v at R35 which you measure low. Measure voltages at Q5 and
                    > Q4.
                    > I suppose the low S12v may cause this but I can't see why. A low supply
                    > would normally mean everything supplied by it would be low.
                    >
                    > The common thing between these two is T3. But the voltages you give do not
                    > seem to make incorrect wiring of this this a suspect.
                    >
                    >
                    > 73 Alan G4ZFQ
                    >
                  • Alan
                    ... From: jamesdee3721 Subject: [softrock40] Re: RXTX ensemble help ... James, Glad you ve found part of the problem. If all the measurements
                    Message 9 of 14 , Mar 7, 2011
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                      ----- Original Message -----
                      From: "jamesdee3721" <xvf@...>
                      Subject: [softrock40] Re: RXTX ensemble help


                      > It turned out that Q4 was bad and was shorting to ground, replaced it and
                      > that obviously helped the bias/voltage issues.
                      >
                      > The problem now is that while the RF output scales with the Rocky I/Q
                      > amplitude it tops out at 0.25v sadly measured at the norcal load.
                      >
                      > Updated measurements are more in line with the builders notes, I've
                      > checked the TX opamp voltages and they are all in line. The soundcard feed
                      > it also correct.
                      >

                      James,
                      Glad you've found part of the problem.
                      If all the measurements are correct I'm not sure.
                      Have you set the soundcard levels?
                      If so, then you would benefit from some sort of signal measurement, a scope
                      or a diode probe may show something.

                      I started making this page, not finished yet, but perhaps it will help?

                      http://sites.google.com/site/g4zfqradio/levels-measured-in-a-softrock-tx

                      73 Alan G4ZFQ
                    • jamesdee3721
                      Sound card levels are in line, in fact with the fault I was hitting 10v on the dummy load as expected with the fault surprisingly but now, barely anything. I m
                      Message 10 of 14 , Mar 7, 2011
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                        Sound card levels are in line, in fact with the fault I was hitting 10v on the dummy load as expected with the fault surprisingly but now, barely anything. I'm wondering in all my poking and lifting something go nudged.

                        I took a look at your page and I'm sure it will help, I'm going to see if I can gain access to a scope. My main concern is if levels at L1/C21 are "ok" then I'm stumped as to what to check next. 0.25V topping out on the output seems amazingly low and yet the conductivity along the path seems there.

                        James

                        --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                        >
                        >
                        > ----- Original Message -----
                        > From: "jamesdee3721" <xvf@...>
                        > Subject: [softrock40] Re: RXTX ensemble help
                        >
                        >
                        > > It turned out that Q4 was bad and was shorting to ground, replaced it and
                        > > that obviously helped the bias/voltage issues.
                        > >
                        > > The problem now is that while the RF output scales with the Rocky I/Q
                        > > amplitude it tops out at 0.25v sadly measured at the norcal load.
                        > >
                        > > Updated measurements are more in line with the builders notes, I've
                        > > checked the TX opamp voltages and they are all in line. The soundcard feed
                        > > it also correct.
                        > >
                        >
                        > James,
                        > Glad you've found part of the problem.
                        > If all the measurements are correct I'm not sure.
                        > Have you set the soundcard levels?
                        > If so, then you would benefit from some sort of signal measurement, a scope
                        > or a diode probe may show something.
                        >
                        > I started making this page, not finished yet, but perhaps it will help?
                        >
                        > http://sites.google.com/site/g4zfqradio/levels-measured-in-a-softrock-tx
                        >
                        > 73 Alan G4ZFQ
                        >
                      • Alan
                        ... Subject: [softrock40] Re: RXTX ensemble help ... James, My suggestion is to set the audio level near my figure and go through until your reading varies
                        Message 11 of 14 , Mar 8, 2011
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                          ----- Original Message -----

                          Subject: [softrock40] Re: RXTX ensemble help


                          > I took a look at your page and I'm sure it will help, I'm going to see if
                          > I can gain access to a scope. My main concern is if levels at L1/C21 are
                          > "ok" then I'm stumped as to what to check next. 0.25V topping out on the
                          > output seems amazingly low and yet the conductivity along the path seems
                          > there.
                          >

                          James,

                          My suggestion is to set the audio level near my figure and go through until
                          your reading varies greatly from mine.
                          Then you will know approximately where the fault lies.

                          But first it might be an idea to look carefully at solder joints,
                          particularly at the coils.

                          I am reluctant to recommend an oscilloscope, it is the best tool for this
                          purpose but a simple diode probe would be quite adequate. Make one with a
                          sharp needle for the probe tip. And the pen case you use must have a cap!!
                          I will make one like that I linked to and put the results on my page.
                          Most testing can be done without a scope, mine sits on a shelf for months
                          (years?) without being switched on.
                          Testing with a scope often gives puzzling results. Recently someone posted a
                          really superb scope picture but it was 3 weeks before another person
                          interpreted it correctly! The fault? An audio connection.

                          73 Alan G4ZFQ



                          >>
                          >>
                          >> > It turned out that Q4 was bad and was shorting to ground, replaced it
                          >> > and
                          >> > that obviously helped the bias/voltage issues.
                          >> >
                          >> > The problem now is that while the RF output scales with the Rocky I/Q
                          >> > amplitude it tops out at 0.25v sadly measured at the norcal load.
                          >> >
                          >> > Updated measurements are more in line with the builders notes, I've
                          >> > checked the TX opamp voltages and they are all in line. The soundcard
                          >> > feed
                          >> > it also correct.
                          >> >
                          >>
                          >> James,
                          >> Glad you've found part of the problem.
                          >> If all the measurements are correct I'm not sure.
                          >> Have you set the soundcard levels?
                          >> If so, then you would benefit from some sort of signal measurement, a
                          >> scope
                          >> or a diode probe may show something.
                          >>
                          >> I started making this page, not finished yet, but perhaps it will help?
                          >>
                          >> http://sites.google.com/site/g4zfqradio/levels-measured-in-a-softrock-tx
                          >>
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