BB414 Pickup/Wiring Problem

[uncle psychosis]

Hey folks

My BB414 has developed a problem with the J pickup.

For those of you not familiar with the BB414, its a passive PJ with master volume, master tone, 3 way switch.

It has recently developed (overnight, in fact) a massive hum/buzz from the J pickup. Here are the symptoms;

1. Buzzes very, very loudly when the J pickup is soloed. The buzz goes away when I turn the volume all the way down. Turning the tone knob just changes the tone of the buzz.

2. Buzzes less loudly in the middle position

3. Doesn't buzz at all when the P is soloed.

4. Buzzing is unaffected by me touching the strings, bridge, etc.

5. Buzzing goes away if I rotate the bass 90 degrees.

6. I haven't changed anything else in my setup, same cable, same gear, same seat, same equipment nearby. This is a new issue.

7. No wires or connections are visibly broken inside the control cavity.

Any ideas on debugging the source of the problem? I've got a voltmeter and a physics degree so I should be able to fix it myself... The fact the buzzing goes away when I move the bass makes me worry my neighbours have a new router or something through the wall. Wouldn't this affect the P pickup though?

Also, does anyone have a wiring diagram for a BB414?

[SubsonicSimpleton]

Normally split P type pickups are humcancelling as the two halves of the pickup function like a humbucker with respect to interference, and J type are a plain single coil and susceptible to hum. Changing the orientation of the bass to the source of interference can change how severe the interference is, so I would expect the issue to be in the environment, and not the instrument.

[SlapbassSteve]

As above, although for my money you should perhaps try a new cable. My brother had grounding issues with a bass for ages and was trying everything to fix it on the bass, but a new cable solved the problem instantly.