Most companies will not send schematics of the equipment to people that are not authorized repair service centers for the very real reason that in lots of places, other will copy the design, place their own label on it and sell it under another name.
Until this issue goes away, I can really understand the serious reluctance to provide schematics.
A good service technician can diagnose and repair problems with amps. Protection circuitry on the other hand is a problem.
You may have to pay the costs of shipping the unit to the factory for repair. it is definitely worth it.
enjoy