Hi there, absolute newbie to everything discussed here so bear with me. Just picked up an old dirty M-06 for to improve my repair skills - after a few good cleanings everything seems to work great, except that the headphone pot is still pretty crackly. It also gets a solid hum when it's set too low, not sure what that's about as the grounding seemed to be in good condition otherwise. Figure the best thing would be to just replace the pot, but the M-06 manual I've found doesn't have a parts list. Any pointers?