The input section has severe AC hum when recording via the Microphone
& direct line but playback through the output & headphone jacks is
fine. If anybody is familiar with working on these any help with
listing the usual high failure suspects & what parts should be
upgraded would be greatly appreciated. I just moved & misplaced my ESR
tester so I'll definitely need to find it to test all the old caps in
this one some of which obviously need to be replaced. I tried printing
out the schematic off the net but for some reason my computer
(Powerbook G4) wouldn't print it. I repaired TVs/VCRs/stereos for 35
years but not many vintage tube audio units.

Thanks, Mark