I have an STR-6800SD Owner's Instruction Manual-is that what you're looking for? It does not have any circuit diagrams, just single line schematics of the tuner and amp sections. Right now I'm looking for a power transformer-mine just died (according to the local repair shop). They say that parts are no longer available-I don't know why not, I just bought this unit back in March of 1977. Any idea who might have parts? Thanx