Fender Deluxe Series Nashville Power Tele humming... HELP

[bongoben]

Okay, so a few months back I picked up a 2000 Nashville Deluxe Series Power Telecaster... and I love it. It has 3 pickups plus the Fishman piezo's. The 5-way switch for the 3 magnetic pups can select (1) bridge, (2) bridge+middle, (3) middle, (4) middle+neck, (5) neck. I plan on eventually modding it so the 3rd position (middle) would actually be bridge+neck but I haven't gotten there yet. My question is that I noticed some serious hum just recently when the selector switch is on the 1st, 3rd, or 5th position... so basically any of the positions where it is only using one pickup. I pulled out the input jack and the knob/switch plate to check for a broken connection. I did find that the ground line at the input jack was holding on by only a couple strands of wire so I re-wired/soldered all 4 connections there but that didn't fix the hum. Nothing in the house has changed that would have caused this to just start. I've tested it on a couple different amps, a couple different outlets (different circuits), with multiple different cables, and with/without it running through my pedalboard. So what am I missing? I haven't pulled up the pickguard yet but can do that soon as I need to change the strings soon anyways. The worst hum comes when it is just on the bridge pickup but the fact that it hums pretty noticeably on each of the "only 1 pickup" switch positions makes me feel like something else is up. Any ideas? Anywhere I should look first? Thanks!

[funsize]

mixed single coils (positions 2 and 4) are naturally hum-cancelling positions so you almost always have more noise on the "only 1 pickup" settings. Check the universal ground (from the volume pot, which I think on Teles is under the bridge plate).