[R-390] R-390 Problems

[David C. Hallam]

I have a problem with my R-390 nonA and don't know exactly where to start.
The radio went dead.  I suspected a B+ problem and found that one of the
26Z5W rectifiers had gone bad.  I replace both and now can measure 180 VDC
at the test point for regulated B+.  The radio still is dead.

Symptoms;

No movement in either the line audio or carrier level meters on any band
with either manual or automatic gain

No noise on the local audio output at any setting of the audio gain control

455 kHz signal from my URM-25D applied to test point E210 (grid of the 3rd
mixer) produces the expected output measured with the 410B at the diode load
terminal until the pass band is increased to 8 kHz or 16kHz.  Then it's like
something breaks into oscillation as the diode load voltage increases to
something like 100 or more volts.

I guess the next step is to start checking the voltages at each tube, but I
wondered if someone might have an idea as to a specific location to
concentrate on.

David C. Hallam
KC2JD