The Switch should be an easy fix?
unplug mains, find the offending switch (i'd do em all while i got it open and check the belts too) underneath most rotary switchs theres a small access hole. Spray switch cleaner into the hole with the dip tube that comes with the can. Rotate the volume switch endlessly. and leave to dry.
reassemble the case and you should be good to go. do not use isopropol alcohol or wd40 on switches.