All it takes is one dirty or corroded (or tarnished) contact to attenuate the signal. Worse the smaller the signal is, so tone controls, tape monitor switches, and volume pots or separate/integrated switches are the worse.
Burned relay contacts will cause all sorts of issues, and replacement is the best solution. Unless you happen to have the ability to re-plate the contacts with platinum/rhodium or whatever the noble metal alloy is. Telephone companies back in the day had service kits for that since their equipment used hundreds of thousands of contactors (old pulse dial stepper switches for instance).
Be very careful with cleaning carbon track potentiometers with D5, and do NOT use D100 -- it seems to soften up the traces somehow and they simply vanish, leaving you with no contact between wiper and base and essentially nothing but full volume.
Burned relay contacts will cause all sorts of issues, and replacement is the best solution. Unless you happen to have the ability to re-plate the contacts with platinum/rhodium or whatever the noble metal alloy is. Telephone companies back in the day had service kits for that since their equipment used hundreds of thousands of contactors (old pulse dial stepper switches for instance).
Be very careful with cleaning carbon track potentiometers with D5, and do NOT use D100 -- it seems to soften up the traces somehow and they simply vanish, leaving you with no contact between wiper and base and essentially nothing but full volume.
