McIntosh tube amplifier diagram

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

@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.

@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. 

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.