Hum in NAD 7020


2010-02-20 11:57 am
Someone gave me a 25-year-old NAD 7020 receiver that has a loud hum and no signal in one channel's output. When I bypass the output amplifier and take signal off the preamp to a separate amplifier I get both channels, so I know the problem is somewhere in the output amplification stage.

I have the service manual and schematics, and I intend to completely recap the unit. I know that hum of the kind I am hearing is a classic symptom of a bad capacitor, but how likely is it that it could be one of the output transistors that has gone bad?

Replies from anyone who has experience with this model will be greatly appreciated, and if anyone else can give me an educated guess, I would appreciate that also. Thanks to all who respond.