McIntosh tube amplifier diagram

McIntosh site only shows owners manual download for your model (no schematics). I would write the factory requesting a service manual, see what they say.

@emergingsoul 

Call the guys in Vestal.  I have talked to them a few times, but never with anything as technical as what you are looking at.  They are close to the McIntosh factory and I consider them the ones that know McIntosh as well as McIntosh or as close as anyone can be.  Good luck. 

@hoosierinohio 

Very helpful and service manuals include schematics which is cool.

Probably should try to get a service manual for the MC 901.  But the MC275 schematic is helpful.  i can follow some of the flow but I need to find someone to walk me through it.

Otherwise, you might try the guys at Audio Classics in Vestal, NY.