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SR Lite short to ground

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  • tsmithers@cix.co.uk
    So far I ve built SR Lite s for 160, 80 and 40 without any problem. However, having just completed the 20m version I appear to have a short to ground somewhere
    Message 1 of 5 , May 2, 2007
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      So far I've built SR Lite's for 160, 80 and 40 without any problem. However, having
      just completed the 20m version I appear to have a short to ground somewhere and
      for the life of me I can't see where it might be.

      The only clue I can offer is that I get 497R (instead of approx 790R) on the
      secondary of T1 to ground - does this ring any bells with anyone or point to a
      possible problem area.

      73 to all
      Trevor G0KTN
    • DSNman@comcast.net
      ... From: tsmithers@cix.co.uk Trevor, I just had problems similar with mine only the resistance went down after it was running for a while. Turned out to be a
      Message 2 of 5 , May 2, 2007
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        -------------- Original message ----------------------
        From: tsmithers@...

        Trevor,

        I just had problems similar with mine only the resistance went down after it was running for a while. Turned out to be a bad .1uf chip capacitor on the center tap to ground.

        Loren WA7SKT


        >
        > The only clue I can offer is that I get 497R (instead of approx 790R) on the
        > secondary of T1 to ground - does this ring any bells with anyone or point to a
        > possible problem area.
        >
        > 73 to all
        > Trevor G0KTN
      • Ford Peterson
        I had a similar problem with mine. When you wind those tiny cores, it is possible to scratch off the enamel and induce a short. It s almost impossible to
        Message 3 of 5 , May 2, 2007
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          I had a similar problem with mine.  When you wind those tiny cores, it is possible to scratch off the enamel and induce a short.  It's almost impossible to diagnose properly.  A 'short' between windings is caused by 2 areas of wire having enamel problems.  While this no doubt happens in almost all transformers, it takes just the right combination of two adjacent areas to induce a short.  The action of lifting leads of the transformer to test the windings with an ohm meter may likely 'heal' the short.  The solution?  Just rewind T1 and see if it helps.
           
          Ford-N0FP
           
           


          From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of tsmithers@...
          Sent: Wednesday, May 02, 2007 9:15 AM
          To: softrock40@yahoogroups.com
          Cc: tsmithers@...
          Subject: [softrock40] SR Lite short to ground

          So far I've built SR Lite's for 160, 80 and 40 without any problem. However, having
          just completed the 20m version I appear to have a short to ground somewhere and
          for the life of me I can't see where it might be.

          The only clue I can offer is that I get 497R (instead of approx 790R) on the
          secondary of T1 to ground - does this ring any bells with anyone or point to a
          possible problem area.

          73 to all
          Trevor G0KTN

        • natsystems
          This is interesting to me Trevor as I measured the same point at 640 ohms but carried on because the unit was working after a fashion . I m the one that
          Message 4 of 5 , May 2, 2007
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            This is interesting to me Trevor as I measured the same point at 640
            ohms but carried on because the unit was working 'after a fashion'. I'm
            the one that posted the SR40 Lite being a bit deaf message, but since I
            did that, the unit here has stopped receiving even the faint
            transmissions I was getting at first. After checking everything I could
            think of and am capable of testing, I was tempted to replace either U4
            or U5 but I couldn't judge which one to focus on first. Now that I've
            read your message thread, I'm going to check out the caps c19&20 that
            are directly connected to the secondary of T1, just like Loren has
            hinted at. I'm not near a soldering iron at the moment so that'll have
            to wait till tomorrow.

            Good luck with yours ....

            73's ... Tom GM4DOZ


            --- In softrock40@yahoogroups.com, tsmithers@... wrote:
            >
            > So far I've built SR Lite's for 160, 80 and 40 without any problem.
            However, having
            > just completed the 20m version I appear to have a short to ground
            somewhere and
            > for the life of me I can't see where it might be.
            >
            > The only clue I can offer is that I get 497R (instead of approx 790R)
            on the
            > secondary of T1 to ground - does this ring any bells with anyone or
            point to a
            > possible problem area.
            >
            > 73 to all
            > Trevor G0KTN
            >
          • tsmithers@cix.co.uk
            Ford, Tom, Loren, Thanks for your comments and advice - much appreciated. I ve rewound T1 and removed and checked C19/20 without any difference. I m now
            Message 5 of 5 , May 3, 2007
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              Ford, Tom, Loren,

              Thanks for your comments and advice - much appreciated.

              I've rewound T1 and removed and checked C19/20 without any difference. I'm now
              wondering if I might have killed one of the IC's. There is a definite short to ground
              somewhere on the board but I can't see it.

              Anyway, short of removing and checking each component in turn I've ordered a
              new kit from Tony. At �5.68 (GBP) incl postage its a bargain.

              73 to all
              Trevor G0KTN
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