After many hours of work, I finally got my Yamaha P-2200 into a state worthy of being tested. The left channel is 100 % original, save for new electrolytic capacitors. It should be fairly representative of a completely original unit. The right channel has received major repairs. The high vol = FS noise floor on the right channel is not due to the repairs done to the amplifier, but rather the factory wiring of the amplifier; it’s mostly made up of 50 Hz hum. There’s probably a signal wire going too close to the transformer, somewhere.
All in all, the Yamaha P-2200 is a very well-performing amplifier, especially for its age and the fact that it’s Yamaha’s first ever dive into the world of PA amps. With plenty of passively-cooled power, tank-like build quality, an impressive noise floor and a good damping factor to boot, Yamaha made sure to make their PA power amp début one for the ages!