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Re: RXTX 6.3 strange problem

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  • barrymichels
    I cannot identify the startup frequency without the PIC. It looks the same in Rocky as with the PIC installed (nothing but the center spike). Once powered
    Message 1 of 25 , Dec 1, 2009
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      I cannot identify the startup frequency without the PIC. It looks the same in Rocky as with the PIC installed (nothing but the center spike). Once powered up, I can tune to the same frequency (56.32 / 4 = 14.08) and see plenty of signals, so it's probably not starting up with that frequency. Unfortunately, my old scope is unreliable above a few Mhz.

      Yes, the current meter is a sure-fire way to start it up. Works every time.

      Barry

      --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
      >
      >
      > ----- Original Message -----
      > From: "barrymichels"
      > Subject: [softrock40] Re: RXTX 6.3 strange problem
      >
      >
      > > When it powers up, there is a clock on the QSE test points.
      >
      > What does it do with no PIC? The Si570, if it is one from Tony, should start
      > at 56.32Mhz for 20m RX.
      >
      > >Yesterday, I used the current meter to power the system up and then left
      > it running all day listening to the WSPRnet.
      > >
      >
      > Well it will add small amounts of resistance and inductance in series, the
      > leads will have some capacitance to the rest of the circuit. The Softrocks
      > are so well decoupled I find it difficult to see this making a difference.
      > Does this always start it?
      >
      > 73 Alan G4ZFQ
      >
    • visierl
      This might not apply to you, but a similar kind of problem. I recently completed my RXTX 6.3 (well, I am there except I haven t built any PA/Filter boards
      Message 2 of 25 , Dec 1, 2009
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        This might not apply to you, but a similar kind of problem. I recently completed my RXTX 6.3 (well, I am there except I haven't built any PA/Filter boards yet, so no transmit yet) and I was seeing a very intermittent failure where, suddenly, the LO would stop running. If I touched the 3.3V test point with a scope probe, it would start up again. I had all kinds of weird theories, none of which panned out. Eventually, it stopped more or less altogether, and after messing around quite a bit I decided I might have damaged the Si570. Before I pulled the part (since I didn't have a replacement) I took a really good look at the solder joints and found that most of the joints were well supplied with solder, but the VDD pin was a bit thin. I flooded in a bit more solder, and problem solved.

        There were comments in the build notes about the Si570 being easy to solder starve, but since it had worked well all along until late in the build, I had figured I was okay there. The explanation of the scope probe effect was mechanical. When I probed the 3.3V test point I slightly deflected the board and restored contact.

        Here were the measured symptoms: when the Si570 was not getting power, I would see about 24 mA on the 12V input. When the Si570 was getting power I would see between 90 and 102 mA. When it got to mostly dead, I would leave it sitting powered off for a while and it might come on for a short time before it stopped. I would see the meter go up to 100 or so then drop to 24 or so.

        It is tough to see whether the joint is solid on the Si570. What I decided was good to see was a good amount of solder buttressed up against the contact on the side of the case (and flowed onto it). Flowed under is not good enough from what I can tell.

        Just my $0.02.

        Eric
        AC0OP

        --- In softrock40@yahoogroups.com, "barrymichels" <bmichels@...> wrote:
        >
        > I cannot identify the startup frequency without the PIC. It looks the same in Rocky as with the PIC installed (nothing but the center spike). Once powered up, I can tune to the same frequency (56.32 / 4 = 14.08) and see plenty of signals, so it's probably not starting up with that frequency. Unfortunately, my old scope is unreliable above a few Mhz.
        >
        > Yes, the current meter is a sure-fire way to start it up. Works every time.
        >
        > Barry
        >
        > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
        > >
        > >
        > > ----- Original Message -----
        > > From: "barrymichels"
        > > Subject: [softrock40] Re: RXTX 6.3 strange problem
        > >
        > >
        > > > When it powers up, there is a clock on the QSE test points.
        > >
        > > What does it do with no PIC? The Si570, if it is one from Tony, should start
        > > at 56.32Mhz for 20m RX.
        > >
        > > >Yesterday, I used the current meter to power the system up and then left
        > > it running all day listening to the WSPRnet.
        > > >
        > >
        > > Well it will add small amounts of resistance and inductance in series, the
        > > leads will have some capacitance to the rest of the circuit. The Softrocks
        > > are so well decoupled I find it difficult to see this making a difference.
        > > Does this always start it?
        > >
        > > 73 Alan G4ZFQ
        > >
        >
      • Alan
        ... From: barrymichels Subject: [softrock40] Re: RXTX 6.3 strange problem ... Can you hear the output on an external receiver? 56.32Mhz is covered by many
        Message 3 of 25 , Dec 2, 2009
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          ----- Original Message -----
          From: "barrymichels"
          Subject: [softrock40] Re: RXTX 6.3 strange problem


          >I cannot identify the startup frequency without the PIC. It looks the same
          >in Rocky as with the PIC installed (nothing but the center spike). Once
          >powered up, I can tune to the same frequency (56.32 / 4 = 14.08) and see
          >plenty of signals, so it's probably not starting up with that frequency.

          Can you hear the output on an external receiver? 56.32Mhz is covered by many
          modern RXs, certainly 14.08 should be heard.
          It seems you are unable to measure the current in the fault condition. Have
          you tried running the Softrock from another power source?

          You need to establish logically what is not working. Try running through the
          tests on Robby's site. http://www.wb5rvz.com/sdr/RXTX_V6_3/ Use a 12V
          supply. The voltages on the dividers will indicate if an output from the
          Si570 is getting that far.
          My guess is a bad joint somewhere, but where? No-one else has commented on
          the current meter "cure"...

          73 Alan G4ZFQ
        • barrymichels
          I have not tested with another receiver yet... I just reflowed the solder around the Si570 and powered it up with a bench supply instead of a battery pack. It
          Message 4 of 25 , Dec 2, 2009
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            I have not tested with another receiver yet...

            I just reflowed the solder around the Si570 and powered it up with a bench supply instead of a battery pack. It powered up immediately. All the voltages are correct. Then I disconnected one of the power terminals and re-connected: it didn't work. I powered down the bench supply and drained the capacitors. When I powered it up again by flipping on the bench supply, it works. Maybe my RXTX needs a soft start? Wonder if the PIC brown-out circuit is the culprit?

            Barry

            --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
            >
            >
            > ----- Original Message -----
            > From: "barrymichels"
            > Subject: [softrock40] Re: RXTX 6.3 strange problem
            >
            >
            > >I cannot identify the startup frequency without the PIC. It looks the same
            > >in Rocky as with the PIC installed (nothing but the center spike). Once
            > >powered up, I can tune to the same frequency (56.32 / 4 = 14.08) and see
            > >plenty of signals, so it's probably not starting up with that frequency.
            >
            > Can you hear the output on an external receiver? 56.32Mhz is covered by many
            > modern RXs, certainly 14.08 should be heard.
            > It seems you are unable to measure the current in the fault condition. Have
            > you tried running the Softrock from another power source?
            >
            > You need to establish logically what is not working. Try running through the
            > tests on Robby's site. http://www.wb5rvz.com/sdr/RXTX_V6_3/ Use a 12V
            > supply. The voltages on the dividers will indicate if an output from the
            > Si570 is getting that far.
            > My guess is a bad joint somewhere, but where? No-one else has commented on
            > the current meter "cure"...
            >
            > 73 Alan G4ZFQ
            >
          • barrymichels
            Just now tested with a receiver. I can hear a carrier on 14.08 when in the failure mode that goes away when I remove power. But, Rocky shows no signals!
            Message 5 of 25 , Dec 2, 2009
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              Just now tested with a receiver. I can hear a carrier on 14.08 when in the failure mode that goes away when I remove power. But, Rocky shows no signals! Doing a "soft start" to get the RXTX working again, and then tuning to 14.08, I see a bunch of signals in Rocky.


              Barry

              --- In softrock40@yahoogroups.com, "barrymichels" <bmichels@...> wrote:
              >
              > I have not tested with another receiver yet...
              >
              > I just reflowed the solder around the Si570 and powered it up with a bench supply instead of a battery pack. It powered up immediately. All the voltages are correct. Then I disconnected one of the power terminals and re-connected: it didn't work. I powered down the bench supply and drained the capacitors. When I powered it up again by flipping on the bench supply, it works. Maybe my RXTX needs a soft start? Wonder if the PIC brown-out circuit is the culprit?
              >
              > Barry
              >
              > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
              > >
              > >
              > > ----- Original Message -----
              > > From: "barrymichels"
              > > Subject: [softrock40] Re: RXTX 6.3 strange problem
              > >
              > >
              > > >I cannot identify the startup frequency without the PIC. It looks the same
              > > >in Rocky as with the PIC installed (nothing but the center spike). Once
              > > >powered up, I can tune to the same frequency (56.32 / 4 = 14.08) and see
              > > >plenty of signals, so it's probably not starting up with that frequency.
              > >
              > > Can you hear the output on an external receiver? 56.32Mhz is covered by many
              > > modern RXs, certainly 14.08 should be heard.
              > > It seems you are unable to measure the current in the fault condition. Have
              > > you tried running the Softrock from another power source?
              > >
              > > You need to establish logically what is not working. Try running through the
              > > tests on Robby's site. http://www.wb5rvz.com/sdr/RXTX_V6_3/ Use a 12V
              > > supply. The voltages on the dividers will indicate if an output from the
              > > Si570 is getting that far.
              > > My guess is a bad joint somewhere, but where? No-one else has commented on
              > > the current meter "cure"...
              > >
              > > 73 Alan G4ZFQ
              > >
              >
            • barrymichels
              Sorry for all the messages in quick succession... Just for kicks, I put a 100 ohm resistor in-line with the power supply. It works every time without the need
              Message 6 of 25 , Dec 2, 2009
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                Sorry for all the messages in quick succession...

                Just for kicks, I put a 100 ohm resistor in-line with the power supply. It works every time without the need to drain the bench supply's caps.


                Barry
              • Alan
                ... From: barrymichels Subject: [softrock40] Re: RXTX 6.3 strange problem ... That might solve your problem if it was not a TX! This is not normal, I suggest
                Message 7 of 25 , Dec 2, 2009
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                  ----- Original Message -----
                  From: "barrymichels"
                  Subject: [softrock40] Re: RXTX 6.3 strange problem


                  > I put a 100 ohm resistor in-line with the power supply. It works every
                  > time without the need to drain the bench supply's caps.
                  >
                  >

                  That might solve your problem if it was not a TX!
                  This is not normal, I suggest you do Robby's checks to try to find out what
                  is locking up in the fault condition.
                  Can you measure the current in the fault condition when fed from the 12V
                  supply?


                  73 Alan G4ZFQ
                • barrymichels
                  Unfortunately, that s how I discovered that the current meter makes it power up. I wondered about how much power it was consuming when it wasn t working
                  Message 8 of 25 , Dec 2, 2009
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                    Unfortunately, that's how I discovered that the current meter makes it power up. I wondered about how much power it was consuming when it wasn't working properly and it started behaving. Don't know how to measure the current with it in the failure mode.

                    I'll do all the tests again when I have time...

                    Today I discovered a strange looking signal right above WSPRnet on 30M. After some research, I found out it's JT65A. Decoded some signals from Michigan. Can't wait to get my PA/Filter module built!


                    Barry

                    --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                    >
                    >
                    > ----- Original Message -----
                    > From: "barrymichels"
                    > Subject: [softrock40] Re: RXTX 6.3 strange problem
                    >
                    >
                    > > I put a 100 ohm resistor in-line with the power supply. It works every
                    > > time without the need to drain the bench supply's caps.
                    > >
                    > >
                    >
                    > That might solve your problem if it was not a TX!
                    > This is not normal, I suggest you do Robby's checks to try to find out what
                    > is locking up in the fault condition.
                    > Can you measure the current in the fault condition when fed from the 12V
                    > supply?
                    >
                    >
                    > 73 Alan G4ZFQ
                    >
                  • barrymichels
                    Ok, new info: I started running through all the tests in the builders notes. I got to the PTT test and decided to add the TX LED. That s the fail mode! When
                    Message 9 of 25 , Dec 3, 2009
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                      Ok, new info: I started running through all the tests in the builders notes. I got to the PTT test and decided to add the TX LED. That's the fail mode! When I power it up it is in TX mode immediately. If I do a "soft" start, it stays in RX mode.

                      Still running through the tests to see if I can find out why it starts up in TX...


                      Barry
                    • barrymichels
                      Now it will not power up in RX mode at all. I get 5.7V on R21 hairpin weather PTT_IN is at 12V or not. I ve double checked Q1 to Q4 and the polarity is right
                      Message 10 of 25 , Dec 3, 2009
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                        Now it will not power up in RX mode at all. I get 5.7V on R21 hairpin weather PTT_IN is at 12V or not. I've double checked Q1 to Q4 and the polarity is right on all of them as well as the correct part in the correct location. (didn't cross 3906 and 3904)

                        I'm going to pull Q1 to Q4 and test them off the board.


                        Barry

                        --- In softrock40@yahoogroups.com, "barrymichels" <bmichels@...> wrote:
                        >
                        > Ok, new info: I started running through all the tests in the builders notes. I got to the PTT test and decided to add the TX LED. That's the fail mode! When I power it up it is in TX mode immediately. If I do a "soft" start, it stays in RX mode.
                        >
                        > Still running through the tests to see if I can find out why it starts up in TX...
                        >
                        >
                        > Barry
                        >
                      • Alan
                        ... From: barrymichels Subject: [softrock40] Re: RXTX 6.3 strange problem ... Well done, now we are getting somewhere! R21 hairpin should have two states,
                        Message 11 of 25 , Dec 3, 2009
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                          ----- Original Message -----
                          From: "barrymichels"
                          Subject: [softrock40] Re: RXTX 6.3 strange problem


                          > Now it will not power up in RX mode at all. I get 5.7V on R21 hairpin
                          > weather PTT_IN is at 12V or not.


                          Well done, now we are getting somewhere!
                          R21 hairpin should have two states, approx 12V or 0V. It is switched by Q1
                          which should be either on or off.
                          There is therefore a resistive leak to ground on that point. If connections
                          are all good around Q1 then Q1 is the culprit. There is definitely something
                          wrong around that transistor, it is not working.

                          73 Alan G4ZFQ
                        • g8voip
                          Hi Barry, Have you removed the TX LED you added, and still have the problem? If not, is it possible you have wired it to the base of Q2 and not to the
                          Message 12 of 25 , Dec 4, 2009
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                            Hi Barry,

                            Have you removed the TX LED you added, and still have the problem?

                            If not, is it possible you have wired it to the base of Q2 and not to the collector? That perhaps could pull the base of Q2 down a little and cause it to initially go to TX.

                            73, Bob G8VOI



                            --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                            >
                            >
                            > ----- Original Message -----
                            > From: "barrymichels"
                            > Subject: [softrock40] Re: RXTX 6.3 strange problem
                            >
                            >
                            > > Now it will not power up in RX mode at all. I get 5.7V on R21 hairpin
                            > > weather PTT_IN is at 12V or not.
                            >
                            >
                            > Well done, now we are getting somewhere!
                            > R21 hairpin should have two states, approx 12V or 0V. It is switched by Q1
                            > which should be either on or off.
                            > There is therefore a resistive leak to ground on that point. If connections
                            > are all good around Q1 then Q1 is the culprit. There is definitely something
                            > wrong around that transistor, it is not working.
                            >
                            > 73 Alan G4ZFQ
                            >
                          • barrymichels
                            I m beyond that being the problem... It s installed between R23 and the center pin of the 5V regulator just as the build instructions show. Q2 is bad. I have
                            Message 13 of 25 , Dec 4, 2009
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                              I'm beyond that being the problem... It's installed between R23 and the center pin of the 5V regulator just as the build instructions show.

                              Q2 is bad. I have it off the board. Q1 and Q4 were good, but now the board is pulling 80mA thru a 100 ohm resistor. Q3 was the next to test, but I stopped when I saw the current shoot up.

                              I have to set it aside for now. But, when I get more time, any suggestions on how to proceed? I'm thinking about pulling off the active components one by one until the current goes down. I don't like the idea of desoldering the ICs on the back if nothing is wrong with them...


                              Barry

                              --- In softrock40@yahoogroups.com, "g8voip" <g8voi.reeves59@...> wrote:
                              >
                              > Hi Barry,
                              >
                              > Have you removed the TX LED you added, and still have the problem?
                              >
                              > If not, is it possible you have wired it to the base of Q2 and not to the collector? That perhaps could pull the base of Q2 down a little and cause it to initially go to TX.
                              >
                              > 73, Bob G8VOI
                              >
                              >
                              >
                              > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
                              > >
                              > >
                              > > ----- Original Message -----
                              > > From: "barrymichels"
                              > > Subject: [softrock40] Re: RXTX 6.3 strange problem
                              > >
                              > >
                              > > > Now it will not power up in RX mode at all. I get 5.7V on R21 hairpin
                              > > > weather PTT_IN is at 12V or not.
                              > >
                              > >
                              > > Well done, now we are getting somewhere!
                              > > R21 hairpin should have two states, approx 12V or 0V. It is switched by Q1
                              > > which should be either on or off.
                              > > There is therefore a resistive leak to ground on that point. If connections
                              > > are all good around Q1 then Q1 is the culprit. There is definitely something
                              > > wrong around that transistor, it is not working.
                              > >
                              > > 73 Alan G4ZFQ
                              > >
                              >
                            • g8voip
                              Hi Barry, That sounds pretty bad, bet the 100 ohm resistor is glowing! So with Q2 removed it is still drawing 80mA through the 100 ohm resistor. That would
                              Message 14 of 25 , Dec 4, 2009
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                                Hi Barry,

                                That sounds pretty bad, bet the 100 ohm resistor is glowing!

                                So with Q2 removed it is still drawing 80mA through the 100 ohm resistor. That would mean about an 8V drop across the resistor, so only 4V getting to the input of the board, so nothing is going to run properly like that.

                                I would start by looking if there is a short circuit on the output of either the 5V regulator U4, or the 3.3V regulator U5.

                                The other thing might be if you have one of the 10uF capacitors on the 12V rail fitted the wrong way around.

                                Rather than trying to pull off all of the semiconductors, particularly the SMD ones, remove the 5V regulator first to try and isolate if it is a fault on the 12V or 5V (or 3.3V)rail.

                                Good luck,

                                73, Bob G8VOI



                                --- In softrock40@yahoogroups.com, "barrymichels" <bmichels@...> wrote:
                                >
                                > I'm beyond that being the problem... It's installed between R23 and the center pin of the 5V regulator just as the build instructions show.
                                >
                                > Q2 is bad. I have it off the board. Q1 and Q4 were good, but now the board is pulling 80mA thru a 100 ohm resistor. Q3 was the next to test, but I stopped when I saw the current shoot up.
                                >
                                > I have to set it aside for now. But, when I get more time, any suggestions on how to proceed? I'm thinking about pulling off the active components one by one until the current goes down. I don't like the idea of desoldering the ICs on the back if nothing is wrong with them...
                                >
                                >
                                > Barry
                                >
                                > --- In softrock40@yahoogroups.com, "g8voip" <g8voi.reeves59@> wrote:
                                > >
                                > > Hi Barry,
                                > >
                                > > Have you removed the TX LED you added, and still have the problem?
                                > >
                                > > If not, is it possible you have wired it to the base of Q2 and not to the collector? That perhaps could pull the base of Q2 down a little and cause it to initially go to TX.
                                > >
                                > > 73, Bob G8VOI
                                > >
                                > >
                                > >
                                > > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
                                > > >
                                > > >
                                > > > ----- Original Message -----
                                > > > From: "barrymichels"
                                > > > Subject: [softrock40] Re: RXTX 6.3 strange problem
                                > > >
                                > > >
                                > > > > Now it will not power up in RX mode at all. I get 5.7V on R21 hairpin
                                > > > > weather PTT_IN is at 12V or not.
                                > > >
                                > > >
                                > > > Well done, now we are getting somewhere!
                                > > > R21 hairpin should have two states, approx 12V or 0V. It is switched by Q1
                                > > > which should be either on or off.
                                > > > There is therefore a resistive leak to ground on that point. If connections
                                > > > are all good around Q1 then Q1 is the culprit. There is definitely something
                                > > > wrong around that transistor, it is not working.
                                > > >
                                > > > 73 Alan G4ZFQ
                                > > >
                                > >
                                >
                              • Alan
                                ... From: barrymichels Subject: [softrock40] Re: RXTX 6.3 strange problem ... The first thing to do is to ask yourself what you have done! It was not pulling
                                Message 15 of 25 , Dec 4, 2009
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                                  ----- Original Message -----
                                  From: "barrymichels"
                                  Subject: [softrock40] Re: RXTX 6.3 strange problem


                                  >
                                  > Q2 is bad. I have it off the board. Q1 and Q4 were good, but now the
                                  > board is pulling 80mA thru a 100 ohm resistor. Q3 was the next to test,
                                  > but I stopped when I saw the current shoot up.
                                  >
                                  > I have to set it aside for now. But, when I get more time, any
                                  > suggestions on how to proceed? I'm thinking about pulling off the active
                                  > components one by one until the current goes down.

                                  The first thing to do is to ask yourself what you have done!
                                  It was not pulling that current before so look carefully, have you made a
                                  solder bridge, has a stray blob got somewhere?
                                  Why bother with Q3,4? They could not affect R21 hairpin voltage.

                                  73 Alan G4ZFQ
                                • barrymichels
                                  I pulled the 5V regulator off and it tests fine: 4.99V. The 12V side shows no current flowing with the 5V regulator removed. All the 10uF caps are the
                                  Message 16 of 25 , Dec 4, 2009
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                                    I pulled the 5V regulator off and it tests fine: 4.99V. The 12V side shows no current flowing with the 5V regulator removed. All the 10uF caps are the correct polarity. D1 tests ok. Q1, Q2 and Q4 are still off the board. Just for kicks, I measured resistance from +5 to Gnd and got 71 ohms.


                                    Barry

                                    --- In softrock40@yahoogroups.com, "g8voip" <g8voi.reeves59@...> wrote:
                                    >
                                    > Hi Barry,
                                    >
                                    > That sounds pretty bad, bet the 100 ohm resistor is glowing!
                                    >
                                    > So with Q2 removed it is still drawing 80mA through the 100 ohm resistor. That would mean about an 8V drop across the resistor, so only 4V getting to the input of the board, so nothing is going to run properly like that.
                                    >
                                    > I would start by looking if there is a short circuit on the output of either the 5V regulator U4, or the 3.3V regulator U5.
                                    >
                                    > The other thing might be if you have one of the 10uF capacitors on the 12V rail fitted the wrong way around.
                                    >
                                    > Rather than trying to pull off all of the semiconductors, particularly the SMD ones, remove the 5V regulator first to try and isolate if it is a fault on the 12V or 5V (or 3.3V)rail.
                                    >
                                    > Good luck,
                                    >
                                    > 73, Bob G8VOI
                                    >
                                    >
                                    >
                                    > --- In softrock40@yahoogroups.com, "barrymichels" <bmichels@> wrote:
                                    > >
                                    > > I'm beyond that being the problem... It's installed between R23 and the center pin of the 5V regulator just as the build instructions show.
                                    > >
                                    > > Q2 is bad. I have it off the board. Q1 and Q4 were good, but now the board is pulling 80mA thru a 100 ohm resistor. Q3 was the next to test, but I stopped when I saw the current shoot up.
                                    > >
                                    > > I have to set it aside for now. But, when I get more time, any suggestions on how to proceed? I'm thinking about pulling off the active components one by one until the current goes down. I don't like the idea of desoldering the ICs on the back if nothing is wrong with them...
                                    > >
                                    > >
                                    > > Barry
                                    > >
                                    > > --- In softrock40@yahoogroups.com, "g8voip" <g8voi.reeves59@> wrote:
                                    > > >
                                    > > > Hi Barry,
                                    > > >
                                    > > > Have you removed the TX LED you added, and still have the problem?
                                    > > >
                                    > > > If not, is it possible you have wired it to the base of Q2 and not to the collector? That perhaps could pull the base of Q2 down a little and cause it to initially go to TX.
                                    > > >
                                    > > > 73, Bob G8VOI
                                    > > >
                                    > > >
                                    > > >
                                    > > > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
                                    > > > >
                                    > > > >
                                    > > > > ----- Original Message -----
                                    > > > > From: "barrymichels"
                                    > > > > Subject: [softrock40] Re: RXTX 6.3 strange problem
                                    > > > >
                                    > > > >
                                    > > > > > Now it will not power up in RX mode at all. I get 5.7V on R21 hairpin
                                    > > > > > weather PTT_IN is at 12V or not.
                                    > > > >
                                    > > > >
                                    > > > > Well done, now we are getting somewhere!
                                    > > > > R21 hairpin should have two states, approx 12V or 0V. It is switched by Q1
                                    > > > > which should be either on or off.
                                    > > > > There is therefore a resistive leak to ground on that point. If connections
                                    > > > > are all good around Q1 then Q1 is the culprit. There is definitely something
                                    > > > > wrong around that transistor, it is not working.
                                    > > > >
                                    > > > > 73 Alan G4ZFQ
                                    > > > >
                                    > > >
                                    > >
                                    >
                                  • barrymichels
                                    I ve looked and looked and can t find any solder bridges. I have done surface mount work before and have a fine tip Weller, 0.015 solder, and a large lighted
                                    Message 17 of 25 , Dec 4, 2009
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                                      I've looked and looked and can't find any solder bridges. I have done surface mount work before and have a fine tip Weller, 0.015 solder, and a large lighted magnifier. No blobs anywhere. No need to use solder wick on any of the chips. I can solder the pins individually. I think I must have inadvertently brushed by something metal on my desk and did some damage. Haven't mounted the unit in a case yet.

                                      It was working fine for about a week. Then a few days ago, it started going into TX on power up (I do not have a PA/Filter module). I continued using it by "soft" starting it with a resistor, current meter or drained bench supply. It was drawing the normal 90mA or so on receive. Yesterday, I decided to try to track down the problem and began by removing Q1. It tested ok, so I replaced it with another 3904 I have in my parts bin. Q2 tested bad, but I left it off the board and moved on to Q4. That's when I noticed the current was high. It may have been high earlier, though. Q1 is now back off the board and I'm still getting high current flow with Q1, Q2, and Q4 missing. It's not a dead short since I'm measuring 71 ohms across +5V and Gnd with the 5V regulator missing.


                                      Barry

                                      --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                                      >
                                      >
                                      > ----- Original Message -----
                                      > From: "barrymichels"
                                      > Subject: [softrock40] Re: RXTX 6.3 strange problem
                                      >
                                      >
                                      > >
                                      > > Q2 is bad. I have it off the board. Q1 and Q4 were good, but now the
                                      > > board is pulling 80mA thru a 100 ohm resistor. Q3 was the next to test,
                                      > > but I stopped when I saw the current shoot up.
                                      > >
                                      > > I have to set it aside for now. But, when I get more time, any
                                      > > suggestions on how to proceed? I'm thinking about pulling off the active
                                      > > components one by one until the current goes down.
                                      >
                                      > The first thing to do is to ask yourself what you have done!
                                      > It was not pulling that current before so look carefully, have you made a
                                      > solder bridge, has a stray blob got somewhere?
                                      > Why bother with Q3,4? They could not affect R21 hairpin voltage.
                                      >
                                      > 73 Alan G4ZFQ
                                      >
                                    • Mr Doug -
                                      Ok so that is about 70ma on the 5 volt line. I don t know if this is correct but that would mean the 80 mils through the 100 ohm resister may have not been
                                      Message 18 of 25 , Dec 4, 2009
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                                        Ok so that is about 70ma on the 5 volt line. I don't know if this is correct but that would mean the 80 mils through the 100 ohm resister may have not been wrong. What is the supply voltage? 80ma is about an 8 volt drop with 100 ohms. If the supply voltage was a little greater than 12 volts - say 13.8 or so the 5 volt regulator would still produce the 5V and 70 of the 80 mils would go there.  Assuming the 70ma draw of the 5 volt supply is correct then nothing would be wrong.

                                        The 390x transistors are rugged especially when used within parameters. While it is not impossible for one to fail it is unlikely unless it was stressed in some way.

                                        Doug

                                        --- On Fri, 12/4/09, barrymichels <bmichels@...> wrote:

                                        From: barrymichels <bmichels@...>
                                        Subject: [softrock40] Re: RXTX 6.3 strange problem
                                        To: softrock40@yahoogroups.com
                                        Date: Friday, December 4, 2009, 10:58 AM

                                         

                                        I've looked and looked and can't find any solder bridges. I have done surface mount work before and have a fine tip Weller, 0.015 solder, and a large lighted magnifier. No blobs anywhere. No need to use solder wick on any of the chips. I can solder the pins individually. I think I must have inadvertently brushed by something metal on my desk and did some damage. Haven't mounted the unit in a case yet.

                                        It was working fine for about a week. Then a few days ago, it started going into TX on power up (I do not have a PA/Filter module). I continued using it by "soft" starting it with a resistor, current meter or drained bench supply. It was drawing the normal 90mA or so on receive. Yesterday, I decided to try to track down the problem and began by removing Q1. It tested ok, so I replaced it with another 3904 I have in my parts bin. Q2 tested bad, but I left it off the board and moved on to Q4. That's when I noticed the current was high. It may have been high earlier, though. Q1 is now back off the board and I'm still getting high current flow with Q1, Q2, and Q4 missing. It's not a dead short since I'm measuring 71 ohms across +5V and Gnd with the 5V regulator missing.

                                        Barry

                                        --- In softrock40@yahoogro ups.com, "Alan" <alan4alan@. ..> wrote:
                                        >
                                        >
                                        > ----- Original Message -----
                                        > From: "barrymichels"
                                        > Subject: [softrock40] Re: RXTX 6.3 strange problem
                                        >
                                        >
                                        > >
                                        > > Q2 is bad. I have it off the board. Q1 and Q4 were good, but now the
                                        > > board is pulling 80mA thru a 100 ohm resistor. Q3 was the next to test,
                                        > > but I stopped when I saw the current shoot up.
                                        > >
                                        > > I have to set it aside for now. But, when I get more time, any
                                        > > suggestions on how to proceed? I'm thinking about pulling off the active
                                        > > components one by one until the current goes down.
                                        >
                                        > The first thing to do is to ask yourself what you have done!
                                        > It was not pulling that current before so look carefully, have you made a
                                        > solder bridge, has a stray blob got somewhere?
                                        > Why bother with Q3,4? They could not affect R21 hairpin voltage.
                                        >
                                        > 73 Alan G4ZFQ
                                        >


                                      • barrymichels
                                        Got a little time this evening and went back to trying to figure out what is wrong with my RXTX. Q1 thru Q4 are off the board (only Q2 tested bad). The PIC
                                        Message 19 of 25 , Dec 9, 2009
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                                          Got a little time this evening and went back to trying to figure out what is wrong with my RXTX. Q1 thru Q4 are off the board (only Q2 tested bad). The PIC is pulled, too. I assume it is ok since I can read from and write to it using my programmer. I lifted pin 16 of both the FST3253's. Using a bench supply set to 12.06V: After lifting pin 16 of the TX mixer, current dropped to around 250mA (from about 380mA). After lifting pin 16 of the RX mixer, current dropped to 120mA. I am getting a tone at 14.080, so the divider and si570 are ok. I think I may have brushed something metal across the desk and it put 12V thru the antenna input. I have no PA/Filter module, so I've got an exposed jumper (cut off leg of a resistor) on J2 for RX only.

                                          Is 120mA about what to expect with what's left on the board, or is that too much still? I think I may have to pull the TX opamps unless there's a test to tell if they survived... Also, any pointers on how to test if the FETs (Q7 and Q8) survived?

                                          I think the RX opamp is ok since when it died there was a loud AM station that took over the whole waterfall that wasn't there before. But, then, I wouldn't expect the RX mixer to be blown either...


                                          Thanks,
                                          Barry - KE4JUC
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