This may be a little off topic here, but I'm hoping that someone could steer me in the right direction. I have an old Model 19 Marantz reciever that needs some help. The left channel keeps dropping off. It usually will come back on when you boost the volume up and then reset it, but it is not as it should be. I have all the original paperwork, manual, schematics, etc. and have had it "repaired" (they replaced some diodes), but the problem keeps coming back. Does anyone know of a reputable service provider for such equipment, hopefully as close to Okla. as possible, that might be able to fix this problem for good? Any quidance would be greatly appreciated. Thanks