First off thanks again to the people that replied to my 1/4" jack wiring problem. I got that fixed last night. As I checked my work I noticed a slight hum when I was in the treble position (Epiphone Les Paul), when I put the switch to the rythem or middle position it is fine. could it be that this switch is just on it's way out? Thanks Terry
A couple of questions: Has the wiring to the pickups been redone? and; apart from the hum, does the affected pickup (bridge?) sound different to normal, is it brighter, or thinner?
If any yes's to the above, it could be either the phasing of one of the coils the wrong way round, or a coil being shorted out, leaving just the other as a single coil. Both of these would hum.
Other hum causes can be things like grounding problems, loose wires etc. I can't see how a switch problem would cause a hum however, if the switch was basically working otherwise. You could test it by shorting out certain connections, or temporarily unsoldering it and testing with a multimeter. (these are really cheap these days, highly advisable if you dont already have one)
also, if it's just a SLIGHT hum then there may be no problem. even the best-shielded guitar w/ humbuckers will hum a BIT and the hum is usually more noticeable on the treble pickup because it transfers higher, more audible frequencies.