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70136RE: [softrock40] Issue with Voltage on SoftRock Lite II

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  • CJ McKinney
    Nov 17, 2012

      Thanks for the initial feedback Alan.  I went through and did an inspection of the board and found no problematic soldering or shorts and all components appear to be the correct values.  Then went through and recorded the voltages along all of the circuits to help give a clearer picture of what is happening.  Maybe there is something here I am missing:

      These DC voltages are all taken with respect to ground at the hairpin of the component or on the pin of the IC.


      D1 – 12.7V

      R11 – 5.04V

      R12 – 2.35V

      R13 – 0V

      R14 – 1.79V

      R15 – 4.77V

      R16 – 0V

      R17 – 96mV

      U2-1 – 5.04V

      U2-2 – 0V

      U2-3 – 100.4mV

      U2-4 – 5.04V

      U2-5 – 5.04V

      U2-6 – 0V

      U2-7 – 0V

      U2-8 – 5.04V

      U2-9 – 0V

      U2-10 – 5.04V

      U2-11 – 99.7mV

      U2-12 – 0V

      U2-13 – 5.04V

      U2-14 – 5.05V


      I also get a very clear 19.68Mhz signal on my handheld from the crystal.  I do not get a beat signal on the 4.92Mhz that I would expect if the dividers were functional.  To me it seems that the breakdown is at the LO output on the collector of Q2 or there is not drive from the oscillator to run the dividers.  Hopefully this can help with identification of the issue as I am stumped.


      73, --CJ KC0JM

      ----- Original Message -----
      Subject: [softrock40] Issue with Voltage on SoftRock Lite II

      >I am building a SoftRock Lite II for the K2 IF (19.6875MHz) and am having issues with the voltage at R17, where I get 90mV reading.
      >All other voltages are fine, but the current draw seems low at only 7mA without the resitor. Believing this was just an issue
      >measuring due to the AC not being picked up right by my meter and that I got a signal at the right frequency, I continued on with
      >the dividers, but now I am having voltage issues at the dividers where the non-5V pins are too low or too high.

      But you do not say what your readings are? Robby says that your meter MAY be affected by the RF square waves. The main thing is that
      are the voltages you see close to 5V and 0V?

      73 Alan G4ZFQ

      >This is the second SoftRock Lite II that I have tried to build and came across the exact same problem. Is there something I am
      >missing that needs to be changed for this crystal? Is it possible for the 2N3906 tansistor to be bad (though this would mean both
      >of the ones I received were bad). I am not even sure what to look for as the only item showing issues is the voltage at R17.
      >Thanks in advance for any help.
      > 73, CJ KCoJM
      > ------------------------------------
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