[Heathkit] SB-104A low tx audio problem

[Alexander N. Gerli]

Hi, gang!

Well, now that the rx is working a lot better, I have a new problem - LOW
tx audio. I can get full power in tuneup, that's fine. With the mic level
set at 50%, I can get full-power with a whistle-up. But, nearly nothing
when speaking. I'm using a good Heathkit mobile mic I've had for years, the
Turner 350 that was made for Heath.

Looking at the boards, I suspect something is amiss on Board B, the
Transmit Audio Board. Looking at the schematic, I'm wondering if the Q201,
the quad OP-AMP could be the culprit? This provides the two stages of
amplification. LM3900N chips are pretty common and available. Before I head
to the 'Bay and get one (or maybe my local RS store might have one on a
blister-card), does anyone on the list have any similar experience like
this, and what did you discover?

When I got this 104A three years ago, it ran great and has been a solid
rig. But, as with anything like this, past history is, well, just that.

Thanks tons for your kind help, folks!

73,

Sandy AC1Y