Hello:
The SA series amps are pretty straight forward Push pull amps.There are no proprietary parts used so repairing them is a snap. With changing the transformer and filter caps they can produce 300watts per channel into 2ohms. Rock solid and reliable. I have schematics and bias adjust instructions for the 20-0166 power boards. If yours has 20-0135 boards then just go to the service manual area of this site and down load pages from the BETA series amp which used the same power board.
Don T.