Acoustic Controls 470 amp, No Ch A output, Ch B only distortion output

[maxboost]

Any help appreciated. troubleshooting this for a friend. Acoustic 470 Channel A doesn't work. Channel B only works with Distortion. Thanks

[Enzo]

Isolate the problem. I'd wager it was in the preamp rather than power amp, but both could be at fault.

My first suspect, considering the age, will be all those little small value electrolytics. I'd be replacing all the little 1, 2, 4.7, 10uf caps in the preamp.

Next, that 470 schematic is just covered with DC voltages, go through and see if any are way off.

[maxboost]

Thanks Enzo,
I figure it must be preamp problems considering the B ch works (with dist on).
I'll check more of the electrolytics, and the voltages.
Thanks for the help!