"Dave D" wrote in message
news


Do you still have a short? If so that makes things very easy- a short is
probably the easiest fault there is to diagnose. Simply trace the two PCB
tracks which are shorted and find all other components across these
tracks.
One of them must be shorted out. Is the capacitor in question on the
supply
rail? Check that the new IC you fitted doesn't have any solder bridges,
and
if it has a mica heatsink insulator, make sure it's not damaged. I doubt
it's a shorted cap, but it is possible nonetheless.

I checked for solder bridges on the new IC VERY carefully when I put it in,
as I did also inspect the mica insulator.

It's possible the 470uF capacitor is part of the decoupled supply to the
preamp section, if so it may have a zener diode in parallel to give a
regulated supply. Therefore, check for shorted zeners.

The balance/tone/volume IC (which is basically my entiere 'pre-amp section')
has a zener internally, BUT I see that it also uses an external decoupling
cap on the internally regulated voltage supply... must check which cap
performs this function.

The output ICs no doubt are coupled to the speakers via large electrolytic
capacitors, what is the voltage level on the IC side of this cap with
respect to ground? It should be close to half supply potential. Compare it
with the good side, but take care not to short anything out.

No, no output caps at all. Output pin of amp IC goes directly to RCA plug
via large trace.

Are both output ICs getting a supply? Are they both getting a ground? Have
you measured voltage levels on each pin and compared them with the good
side? Have you downloaded a datasheet for the ICs, found the input pin and
injected a signal there to listen for output? Even touching a finger to
the
input pin may give a buzz from the speaker, or a screwdriver may give a
click. There's ways and means, even without test equipment!

Dave