Sir,
When I bought my sansui au7500 from the previous owner, he told me exactly about the same problem that you were discribing in your post. All he had to do was change some of the transistors whihc appeared to be leaking. Don't know where he had it serviced, but I suggest you also try to PM sir Dana. He's got the 9500 and knows more about these kind of problems. He might be able to help you with it.
Thanks,
eestrera