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Re: Softrock 40 U2 pin voltages low?

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  • kj4otu
    Success! I m now hearing cw quite clearly even with a simple wire antenna. Thanks for your help!
    Message 1 of 7 , Oct 31, 2009
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      Success! I'm now hearing cw quite clearly even with a simple wire antenna. Thanks for your help!

      --- In softrock40@yahoogroups.com, "kj4otu" <kj4otu@...> wrote:
      >
      > I think I found the problem. I'm only getting .14 v in pin 16 of U3 (mixer). There is 5v at the pad just not on the pin. I believe after re-soldering I'll be good to go.....
      >
      >
      >
      > --- In softrock40@yahoogroups.com, "kj4otu" <kj4otu@> wrote:
      > >
      > > Thanks for the reply Tony.
      > >
      > > I'm getting 2.66v at the qsd0 ad qsd1 probe points. I'm also able to clearly hear the 28.224 Mhz signal being generated by the oscillator.I guess the next step is to verify the mixer operation?
      > >
      > > Thanks,
      > >
      > > Jamie
      > >
      > > --- In softrock40@yahoogroups.com, Tony Parks <kb9yig@> wrote:
      > > >
      > > > Hi Jamie,
      > > >
      > > > One way to get a sense of if the divider 74AC74 is being clocked to to
      > > > probe at the QSD clk_0 and QSD clk_1 vias in the middle top surface of
      > > > the board with respect to circuit ground. Each via should have a
      > > > average voltage, DC, of about 2.5 volts. If the 74AC74 is not being
      > > > clocked, please check to make sure the crystal case is not shorting
      > > > between the two vias for the crystal connections. The crystal needs to
      > > > be slightly above the circuit board to prevent the case from shorting
      > > > between the two vias.
      > > >
      > > > 73,
      > > > Tony Parks
      > > > kb9yig@
      > > > http://www.kb9yig.com
      > > >
      > > >
      > > >
      > > > On Sun, 2009-10-25 at 19:40 +0000, g8voip wrote:
      > > >
      > > > >
      > > > >
      > > > > Hi Jamie,
      > > > >
      > > > > I assume you are talking about a 40m version of the SoftRock LiteII?
      > > > >
      > > > > That voltage does sound a little on the low side, but it can be
      > > > > difficult measuring active 'logic' waveforms using a DVM.
      > > > >
      > > > > I just checked on my 40m Lite II here with a DVM and it was 3.8v at
      > > > > that point.
      > > > >
      > > > > If you have access to an oscilloscope, take a look at the waveforms
      > > > > present on U2 pins 3 and 11, also the output pins 6 and 8.
      > > > >
      > > > > Failing that, you should be able to monitor the crystal oscillator
      > > > > frequency around 28.224MHz on a 10m receiver, and if the divider stage
      > > > > is working, you should also be able to hear a signal on 40m around
      > > > > 7.056MHz.
      > > > >
      > > > > If you can do that, then in all probability, you do not have a
      > > > > problem.
      > > > >
      > > > > 73, Bob G8VOI
      > > > >
      > > > > --- In softrock40@yahoogroups.com, "kj4otu" <kj4otu@> wrote:
      > > > > >
      > > > > > The clock pins (3 and 11) on the u2 chip in the divider circuit are
      > > > > showing 2vdc. The docs spec 3.5-4.5 for both. Any idea where I should
      > > > > look or is this even a problem to worry about? I have checked the
      > > > > soldering and it looks great.
      > > > > >
      > > > > > Thanks,
      > > > > >
      > > > > > Jamie
      > > > > > KJ4OTU
      > > > > >
      > > > >
      > > > >
      > > > >
      > > > >
      > > > >
      > > >
      > >
      >
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