Buzzing Pickup

UnclePsychosis

Hey folks

My Yamaha BB414 Bass 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 gets quieter with the volume knob and 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? 

ICBM

It's something in the room/house/outside world. Those are the exact symptoms of it picking up radiated electromagnetic noise from somewhere - the P pickup is humbucking so it won't.

New phone/computer etc nearby?

UnclePsychosis

There's nothing new in my house but my gear is setup next to an adjoining wall. Might be the neighbours. I'll try moving my kit around and see what happens.

Cheers

ICBM

I'd take a bet they've got a new thing with a switch-mode power supply just the other side of the wall - the type of noise they produce is exactly as you describe. Usually, if you turn around with the instrument until you find the point where the buzz stops, the pickup is now pointing directly at the source of the trouble.

The location of the rest of your kit won't make any difference, the noise is being picked up directly by the pickup itself.