Conrad Johnson MF-200

I have been using my sons Conrad Johnson MF-200, he had it stored for about 10 years, when I first started it I used a rheostat and slowly ramped it up. It had been working fine for about a year. Last week I heard something like a buzzing sound or chatter from the amplifier. I shut it down waited for a few minutes and turned it on, again I heard the same noise, also static or popping sound coming from my speakers. I took the cover off and was  shocked to see the dust and even a couple of spiderwebs. I thoroughly cleaned it, hooked up a couple of old 4 ohm speakers and this time played fine. Although both heat sinks ran as hot as they normally do I did notice one was a little cooler. Does anyone have a schematic of this amplifier you can let me have? There are a couple of potentiometers and I’m curious if the bias can be adjusted.