Peavey JSX issues...

[nassosxlvbros]

Hi to all from Athens.
Some strange issues coming out during a repair on a JSX signature amp...
Issues like this:

1st Issue:
If you put a signal on Clean channel everything is OK...You open the Clean volume,open master volume,and plays OK Shut the input volume,no sound...OK so far...BUT...
Volumes on Crunch and Ultra does not shut the sound copletely,only GAIN does this....I believe this is not normal...
2nd Issue: Some annoying "pops" when you select channels...not normal again due to a mute sub circuit...
3rd issue: That effect footswitch board is the main suspect to all this mailfunctions..any ideas?

Thanks in advance...