[Collins] Repair of 75S1 receiver

[Dr. Gerald N. Johnson]

On Sun, 2007-05-27 at 10:48 -0500, Ron Wicker wrote:
> Recently my 75S1 receiver  developed a audio problem The audio is somewhat
> distorted and when the audio gain is advanced to a normal setting, there is
> a whistle or squeal.  The signal is copyable at certain settings.  I have
> checked the tubes and all check OK.Before I tear into the receiver, are
> there common things that I should look for?  Any help/advise would be
> appreciated.
> Thanks, Ron,AA5NI......
> 

Capacitors, first the black beauty coupling audio to the control grid of
the audio output tube. That upsets the bias leading to distortion and
even hotter operation of the tube. Then all the other black beauties
that load the AVC line and let the detector be over driven. They leak
just enough to cause problems. Orange drops are my preferred
replacements.

Then the can electrolytic. Its acting high series resistance or going
nearly open. C59A,B,C, plus C56, C60, and C107.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer