hifi engine

Service Manual and Schematics for Rotel RX-803

Looking for Service Manual and Schematics for Rotel RX-803,
Lost channel and suspect switches due to exposure to high humidity.
Anyone had similar problems?
I have tried cycling the switches countless times and attempted dis-assembly,
but chickened out....Lol !
I bought it as a demo unit in 77.
Many Thanks!
Mike
mikewatson48@yahoo.com