I am understanding from your post that you are experiencing two kinds of noise from your Sansui AU-919, transformer noise and audible noise from the speakers. Is this correct?
Transformer Noise: Have you put your ear near the transformer and you can physically hear it humming? If it is physical transformer hum caused by vibration of the transformer it can be because the glue inside the transformer windings is coming loose with age or it could be because the idle voltage is set incorrectly, causing the transformer to hum (or some combination of these things). Sometimes tightening the mounting screws on the transformer can lessen the vibration but may not fix the underlying problem of why it is vibrating.
Audible Noise from Speakers: What does the noise coming out of the speakers sound like?