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Re: V6.3 RX/TX PTT switching headache

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  • wa3drc_18954
    Ken, sounds like you found that fast! your problem was not as far back as mine. those fet devices are probably not as rugged as the npn and pnp s. Maybe they
    Message 1 of 5 , Mar 19, 2009
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      Ken,

      sounds like you found that fast! your problem was not as far back as mine. those fet devices are probably not as rugged as the npn and pnp's. Maybe they took an ESD hit while you were assembling.

      good luck,
      Ed

      --- In softrock40@yahoogroups.com, kenneth hardy <kenahardy@...> wrote:
      >
      >
      > Ed - thanks your sound advice. Your reply spurred me into
      > action and following your info. I lifted R29/R30 and the
      > PTT circuit worked just fine.
      > Looks as though either Q7 or Q8 has fallen over.
      > I will replace both and hopefully it will be headache solved
      > and on with the build.
      > Thanks again your help.
      >
      > Ken M0XBK
      >
      >
      >
      > To: softrock40@yahoogroups.com
      > From: edfinn1@...
      > Date: Wed, 18 Mar 2009 15:08:35 +0000
      > Subject: [softrock40] Re: V6.3 RX/TX PTT switching headache
      >
      >
      >
      >
      >
      > Ken,
      >
      > I had trouble in this area too a couple weeks ago when I was building my RxTx. I started pulling out the transistors in this area and eventually found a bad npn at q1.
      >
      > I doubt q7 or q8 have any influence, but you could lift a leg on each resistor r29 and r30 to convince yourself of that.
      >
      > If it still acts the same after that (which it probably will), pull out q3. If it still does not work right, you are down to q1 or q2 circuitry. You can test q2 by itself by pulling /PTT IN low with a clip lead to ground. Pulling this low should make S12v go high to near 12v. If it doesn't q2 may be bad.
      >
      > /PTT IN should have been high before doing this, unless q1 is shorted or PTT IN is high. Or in other words, Make sure PTT IN is 0v so that q1 should be off and /PTT IN should float high. If it doesn't q1 may be bad.
      >
      > Anyway, you probably need to pull a few leads and build the circuit up step by step as you convince yourself it is working correctly.
      >
      > hope this helps...
      >
      > Ed wa3drc
      >
      > --- In softrock40@yahoogroups.com, "kenahardy" <kenahardy@> wrote:
      > >
      > >
      > > I have been following Robbies enhanced builders notes for
      > > the V6.3 and have hit a peculiar problem in the PTT switching stage.
      > >
      > > At switch on PTT is normal with no muting:
      > > S12V output measures 0volt
      > > -PTT IN( measured at R21) is 11volt
      > >
      > > However when connecting 12 volt to the PTT-IN the PTT circuit
      > > switches to give:
      > > 11 volt at S12V permanently even when PTT-IN voltage is removed
      > > and 5.4 volt instead of 0volt at -PTT IN
      > >
      > > This state remains even when the PTT voltage is removed.
      > >
      > > I have checked R19 R20 R21 R22 R23 all ok and changed transistors Q1
      > > and Q2 with still the same problem.
      > >
      > > I am running out of ideas - so any help gratefully received.
      > >
      > > Thanks
      > >
      > > Ken M0XBK
      > >
      >
      >
      >
      >
      >
      >
      >
      >
      >
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