[Richard Crowley]

Readily Visible wrote:
The left channel bugged out again and I double confirmed that it is
*not* the speaker relay. I also double confirmed that switching right
and left preamp outputs to left and right power amp inputs
respectively *does not* change which channel drops out, confirming
that the problem is downstream of these connections. Then, with the
left channel out, I sprayed some freeze onto the tranny I suspected
of being at fault, with no results. I then sprayed every other tranny
on the amp board, including the output trannies. No change. Then I
sprayed all the resistors and caps. Then I gave the whole amp board a
general spraying.

Presumably "tranny" means transistor in this context. (It used to mean
transformer in electronics.) It doesn't seem as likely that a transistor
opening (or shorting) would have a reversible effect. In most modern
direct-coupled power amplifiers, a transistor fault will take out most of
the other transistors in the channel and will NOT be reversible after
cooling off.

I got absolutely no reaction.

The channel continues to respond to an increase in volume, that is, it
kicks back in with a crackle when the volume pot is turned just past
the halfway point.

So sending an audio transient into the amplifier does something that
restores the signal path. My suspect list would be: solder joints,
capacitors, resistors.