[R-390] Local & Line potentiometers

[Drew P.]

Craig wrote:

"A little time was spent on the beast this evening.
1: No ground problems at the end of the pots, even added a jumper once
again. No change
2: Checking the audio at the CCW ends, less than 5 millivolts with the
O'scope.

Going to check a few more items tomorrow; swap IF's between the Motorola and
Amelco again. This should rule out AGC issues there. Then on to the RF
section."

I'm not convinced that it could be an AGC problem.  In the couple of R-390A's I've operated, the audio gain pots work normally even in MGC mode (which disables AGC), and with RF gain all the way up and the receiver overloading on a strong signal.

My vote goes for one section of the three section plug-in electrolytic cap being open with resultant loss of decoupling.

Drew