Yamaha C-2a Preamp problem

[Overheated]

Just acquired a Yamaha C-2a preamp with some other gear and it has, I have been told, bad caps/transistors. Here are the symptoms (just in one channel...the other channel has no problem):

Volume knob: noise and woofer pumping in the first 1/10 of its rotation...the rest of the rotation it is fine

Balance knob (concentric to the volume control): causes a bit less noise and woofer pumping

Mute switch: causes a massive woofer pop each time the switch is toggled

Stereo/Mono switch: causes a massive woofer pop each time the switch is toggled

Again, these symptoms are only in one channel...all controls have been cleaned with no improvement (volume control cleaned as best I can w/o opening it as it's sealed).

If I may, a few questions:

- any idea which caps/trannies are the likely offenders?

- is there a source for a high quality schematic?

- is there a source for a service manual?

Thanks for any and all info.

 

[mjf]

hello.
i think jan dupont has a schematic and service manual (at Welcome to Audio Circuit Denmark).
you can compare the working channel with the bad one...........voltage measuring with the multimeter,scope or so................
greetings

 

[Overheated]

Thank you, mjf