hifi engine

Sansui QRX-7001 Service manual

I am looking to make repairs to a very nice vintage Sansui QRX-7001 that I found in my mother in-law’s attic. I am very pleased with how good this thing sounds. Only problem is the right channels front and back, A and B, have low volume are scratchy and has almost no base. I have just enough experience with electronics that I think with a service manual I can fix it. If anybody has a service manual they can share I would appreciate it very much. Any advice is also welcome. Thanks in advance.