Yamaha A-760 of the Natural Sound range

[Layberinthius]

First question, anyone got a schematic they could punch off?

Second, I whole heartedly suspect the power supply capacitors
and a few other decoupling ones merely upon age that is causing
a huge amount of ground loop hum and buzz.

If you disconnect the line cable from any connector, Aux or Tuner,
and hold it in your hand you get a huge amount of hum even though you are not even making conductive contact.

Third, while wired up to a cd player or PC via analog, there is still
a buzz in the background and all sorts of stuff manage to make
it through the power line like spikes from my fridge, tv etc...

I was wondering if there is a schemat and also if anyone has
some modifications available aswell as more information as to
what class it is, A B or a mix? It draws 520watts so I'm suspecting
Class-A Mosfet