Using stereo output jack with passive pickup = earth hum?

[Nolly]

Hey guys,

I've just wired some passive pickups into one of my pupil's guitars, which previously had a set of EMGs in. At the moment I'm getting earth hum when the guitar is plugged in, which stops when I touch any of the pots. I've checked and rechecked every connection and I really can't see anywhere that the wiring is awry.
The only thing I can think of is that the output jack must be stereo for the EMGs, and now that the guitar has passives instead, one of the jack connections (where the battery wire was attached) is no longer connected to anything - could this be the source of the hum?
Any help would be much appreciated!

Nolly

[WezV]

did you attach a ground wire to the bridge?  you dont need it with EMG's but do with passives

sounds like your jack should be alright, you just ignore the extra connection and make sure the hot goes to tip and ground goes to sleeve

[Philly Q]

I don't think there should be any problem with the stereo jack, so long as nothing's connected to the third tag.

Is there a wire connecting the bridge/tailpiece to ground?  The probably wouldn't have been on an EMG guitar.


(Edit:  Redundant post, Wez beat me to it!  :lol: )

[Nolly]

Thanks guys, yeah the bridge is earthed - the guitar originally had passives, then the owner had EMGs professionally installed (very neat job I must say), and now back to passives. I really can't think what it is, hence why the long shot about the stereo jack, very puzzling.

[gingataff]

A lot of Ibanez guitars use stereo TRS jacks as standard so that shouldn't be a problem if you ignore the ring.

[Nolly]

A lot of Ibanez guitars use stereo TRS jacks as standard so that shouldn't be a problem if you ignore the ring.

Thanks, that pretty much lays that idea to rest then. Trial and error may have to be the order of the day.

[WezV]

sounds like you have ground loops going on then

Is the cavity shielded? How? (paint or foil)

Did you do all the grounds to one place?  (star grounding)

[Nolly]

The cavity is paint-shielded, and all the grounds are on one pot (the guitar only has a volume), but not joined together.

[WezV]

it does sound like you have things done right.   

time to get the multimeter out and check continuity between all the ground points...  :?

[Nolly]

Yeah I think so too, thanks for the help though guys!