Is this the same AU-D77X that you mentioned in a previous post- the one in the thrift store for $100?
If so, who took it apart?- the thrift store or the owner who sold (gave, or whatever the situation is) it to the thrift store?
While I do sympathize with your dilemna, I dont understand why you bought it, only to give yourself problems now in trying to fix it.
Unless I've overlooked something, I dont recall you mentioning these problems until now. Had you mentioned it before, I wouldve told you to pass on it, as you can instead spend $100 on another Sansui amp that works properly on Ebay and avoid the headache you have now in trying to get parts/fix the AU-D77X.
Perhaps some other members here can provide some suggestions, but I think you should go after the person who was messing around with the amp, or whatever it is that he did to it so that it got that way, and have him come up with a solution to his problem that you you inherited.