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Re: I think I found my so-called bad chip problem.

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  • KF4BQ
    ... Bill, Don t take this bad: there appears to be some pieces of wire/solder near many of the solder connections in your pictures. Many use a Qtip with
    Message 1 of 9 , Nov 3, 2012
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      --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
      >
      > And, reassembling, the voltages now check out (2.5 everywhere but pin 8 and 4, which are 5v and 0v, and bridged with a resistor also gives the right voltages of 2.75 and 2.25 at 1 and 7). If you examine the pin in question in this picture (the after) you can now see a tiny trace of copper where the board defect was. I broke that trace with a voltmeter probe, and now it all works. Scratch one chip and one capacitor in the process. Hopefully there was a spare.
      >
      > http://imgur.com/oY6qI

      Bill,

      Don't take this bad: there appears to be some pieces of wire/solder near many of the solder connections in your pictures. Many use a Qtip with alcohol to clean up flux and junk. To weak for me; I use Acetone with a Qtip and you can really see any troubles after that. On some heavy flux areas I even use a small brush (trimmed down) to scrub the area. It might save you some future rework.

      73, Mike Collins KF4BQ
    • Alan
      ... Subject: [softrock40] Re: I think I found my so-called bad chip problem. ... Well done. You should have followed Robby s method, and told us the voltages
      Message 2 of 9 , Nov 3, 2012
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        ----- Original Message -----
        Subject: [softrock40] Re: I think I found my so-called bad chip problem.


        > And, reassembling, the voltages now check out (2.5 everywhere but pin 8 and 4, which are 5v and 0v,

        Well done.

        You should have followed Robby's method, and told us the voltages before you did anything more. Zero volts on pin 2 would have
        indicated where the fault was.
        Zero volts on pin 2 is the reason for 5V on pin 1.

        73 Alan G4ZFQ
      • wfahle
        No offense taken; it s my first PCB. I did try rubbing alchohol but it made more of a mess. The whole board is a mess, but especially this part after all the
        Message 3 of 9 , Nov 3, 2012
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          No offense taken; it's my first PCB. I did try rubbing alchohol but it made more of a mess. The whole board is a mess, but especially this part after all the diagnosis I went through to find the fault, including destroying a chip and soldering green wire onto it, etc. It will be a miracle if it works.

          --- In softrock40@yahoogroups.com, "KF4BQ" <mikecol@...> wrote:
          >
          > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
          > >
          > > And, reassembling, the voltages now check out (2.5 everywhere but pin 8 and 4, which are 5v and 0v, and bridged with a resistor also gives the right voltages of 2.75 and 2.25 at 1 and 7). If you examine the pin in question in this picture (the after) you can now see a tiny trace of copper where the board defect was. I broke that trace with a voltmeter probe, and now it all works. Scratch one chip and one capacitor in the process. Hopefully there was a spare.
          > >
          > > http://imgur.com/oY6qI
          >
          > Bill,
          >
          > Don't take this bad: there appears to be some pieces of wire/solder near many of the solder connections in your pictures. Many use a Qtip with alcohol to clean up flux and junk. To weak for me; I use Acetone with a Qtip and you can really see any troubles after that. On some heavy flux areas I even use a small brush (trimmed down) to scrub the area. It might save you some future rework.
          >
          > 73, Mike Collins KF4BQ
          >
        • John
          Use a toothbrush and Isopropyl alcohol and the pcb will look like it just left the factory. John G3UGY From: wfahle Sent: Saturday, November 03, 2012 9:50 PM
          Message 4 of 9 , Nov 4, 2012
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            Use a toothbrush and Isopropyl alcohol and the pcb will look like it just left the factory.
             
            John G3UGY
             

            From: wfahle
            Sent: Saturday, November 03, 2012 9:50 PM
            Subject: [softrock40] Re: I think I found my so-called bad chip problem.

             

            No offense taken; it's my first PCB. I did try rubbing alchohol but it made more of a mess. The whole board is a mess, but especially this part after all the diagnosis I went through to find the fault, including destroying a chip and soldering green wire onto it, etc. It will be a miracle if it works.

          • William Fahle
            Yes, I wish I had been more patient in trying things before starting to unsolder. In particular the solution came from continuity testing with the ohms turned
            Message 5 of 9 , Nov 5, 2012
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              Yes, I wish I had been more patient in trying things before starting
              to unsolder. In particular the solution came from continuity testing
              with the ohms turned up to 200k. This allowed me to see that certain
              circuits were not open, but were in fact 21k, which led to the
              diagnosis. In any case, I learned a lot doing this, so no regrets.

              So far it passes every test; I now discover I need a second soundcard
              to actually use the transmit. Also my primary soundcard is mono in, so
              it is useless as a receiver card, so while I get semi-readable signals
              from a backyard dipole, I'm not 100% sure what the receiver
              performance will be yet, as there are too many variables. A quickly
              thrown-up antenna, a bad soundcard, a new softrock build with problems
              along the way (and no scope to check the output), default calibration,
              all conspire to give me a big screen full of white noise with the
              occasional discernable cw signal, and muddy signals that I can only
              assume are ssb. I'm going to get a USB soundcard for the receiver side
              and use the built-in for transmit and then report back. The built-in
              definitely puts out stereo, so that shouldn't be an issue for
              transmit.
            • pond.james_pond
              You re not alone. Took me several days of frustrated reworking before finding the etch failure. I felt less charitable than yourself at the time.
              Message 6 of 9 , Nov 5, 2012
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                You're not alone. Took me several days of frustrated reworking before finding the etch failure. I felt less charitable than yourself at the time.

                --- In softrock40@yahoogroups.com, William Fahle <billfahle@...> wrote:
                >
                > Yes, I wish I had been more patient in trying things before starting
                > to unsolder. In particular the solution came from continuity testing
                > with the ohms turned up to 200k. This allowed me to see that certain
                > circuits were not open, but were in fact 21k, which led to the
                > diagnosis. In any case, I learned a lot doing this, so no regrets.
                >
                > So far it passes every test; I now discover I need a second soundcard
                > to actually use the transmit. Also my primary soundcard is mono in, so
                > it is useless as a receiver card, so while I get semi-readable signals
                > from a backyard dipole, I'm not 100% sure what the receiver
                > performance will be yet, as there are too many variables. A quickly
                > thrown-up antenna, a bad soundcard, a new softrock build with problems
                > along the way (and no scope to check the output), default calibration,
                > all conspire to give me a big screen full of white noise with the
                > occasional discernable cw signal, and muddy signals that I can only
                > assume are ssb. I'm going to get a USB soundcard for the receiver side
                > and use the built-in for transmit and then report back. The built-in
                > definitely puts out stereo, so that shouldn't be an issue for
                > transmit.
                >
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