Red Wave Radio

> I'm trying to repair a Tempo One HF rig.  It works fine for the
> first 10 to 15 minutes after startup, but after it warms up, it
> loses mic audion on SSB.  Listening on another receiver, you can
> faintly hear some audio if you SCREAM into the mic.  The carrier
> is quite loud, as I would expect (even though it is correctly
> nulled, there is still more than sufficient carrier leakage to
> be heard on a receiver a few inches away!).  I've checked the
> tubes, and all test good (all the ones that might have something
> to do with SSB generation, audion, transmitter, etc).  There are
> no burnt parts or damaged wiring.  Anyone have any ideas on why
> the mic audio is going away?  Obviously it's a heat-related issue.

> Dean - K5DH

> > I'm trying to repair a Tempo One HF rig.  It works fine for the
> > first 10 to 15 minutes after startup, but after it warms up, it
> > loses mic audion on SSB.  Listening on another receiver, you can
> > faintly hear some audio if you SCREAM into the mic.  The carrier
> > is quite loud, as I would expect (even though it is correctly
> > nulled, there is still more than sufficient carrier leakage to
> > be heard on a receiver a few inches away!).  I've checked the
> > tubes, and all test good (all the ones that might have something
> > to do with SSB generation, audion, transmitter, etc).  There are
> > no burnt parts or damaged wiring.  Anyone have any ideas on why
> > the mic audio is going away?  Obviously it's a heat-related issue.

> > Dean - K5DH

> First thing I'd do is replace all tubular capacitors in the audio chain.
> These have a bad habit of going leaky when hot. It's also possible you
> have a tube that goes south when hot. This is difficult (impossible) to
> find using a tester. Could also be a resistor that goes high or open
> when hot. My money's on a cap.

> 73 de Steve, KE4OH
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