[R-390] R-390A trouble

[Bill Hawkins]

Barry, I think you've got it.

But I thought of another thing to try. Because the set is
oscillating within itself, something common to the IF and
RF decks is carrying energy between them. The first thing
to try is a big paper capacitor across the Heater supply
at any convenient point. If that didn't change anything,
try an 0.1 mfd/600 volt across the B+ line (not regulated
B+). If that doesn't change anything, and using the correct
tube in the RF Amp didn't fix it, I think you are left with
a witch hunt for a poor ground. Ah, when you try the bypass
capacitors, try several different ground points.

Or you could try to talk your friend into letting you swap
the RF decks. Do not try this without a manual, though. It
will be an education. But I think that you are looking at
removing your RF deck in any event.

Regards,
Bill Hawkins