http://www.peavey.com/media/pdf/manuals/80370017.pdf

I especially like the part that explains how the "tone circuit" works. remember in "single coil" mode, you will get a 60hz hum.

if the answer doesn't come as simple as that, then I would start looking at a ground, tone cap, volume/tone pot issue. Further more, I would try to make sure it is "shielded" to prevent induction from other nearby electronics.

Possibly the tone knobs. If you run them wide open you will be in single coil mode. Back them off to roughly "7" and you'll be in humbucking mode.

Me, I disconnected my two red wires leading to the tone pots and now I run in humbucking mode all the time. Never sounded better.