I'm having issues setting the bias voltage for the right channel. The
service manual says to set it to 2.5mVDC. I can set the left channel
with no problem, but the right channel drifts badly with warming
up/cooling down etc. The left channel drifts around 2.1-2.8mV whether
it is just warmed up from cold or just cooled down from hot.
If I warm up the amp completely, set the right channel to 2.5, turn it
of and let it get cold, turn it back on & let it warm up, it will be
1.1mV. If I then set it to 2.5, let it sit, it will be up around 9mV.
These aren't exact figures, it drifts pretty widely. It isn't a dirty
pot, the readings aren't jittery or erratic, they just drift with
temperature variations.

I'm not sure what class this amp is, it's definantely not D, it looks
like a standard analog transistor audio amp. What would a normal
cause be for this kind of drift?

Thanks for any help, I'll gladly get more specific definite readings
if they will help.

Thanks,
Steve