New Bass Pickups

Eoin Madsen

I need some help. I just put in a new set of Seymour Duncan Hot Stack pickups into my Fender (Mexican) Jazz Bass. I also replaced the pots and electronics.

The pickups work, but I get a buzzing/humming sound from it which lessens significantly when I'm touching any part of the ground assembly. I first thought that this must be a grounding problem so I checked all the ground connections and resoldered everything. The bridge is connected to ground, the shielding is connected to ground, the three pots are connected to ground, and the jack sleeve is connected to ground. The ground from each of the pickups is connected also. I've disconnected the pickups, cut the wires, restripped them and resoldered them. The hot signal seems to be fine. I've tried it though two different amps and a mixing desk, I've switched leads, and I've tried an amp on two different ring circuits in my house. The tone pot and volume pots work (though the tone pot makes an odd pop sometimes when I turn it) and the general arrangement is as the wiring diagram advised. I've tried bypassing the tone pot with the live signal, and the problem is the same. I've tried disconnecting the bridge ground and the shielding ground, and the problem gets worse. When I turn down the bridge pickup pot the problem is reduced considerably, so I think it's something in the wiring of that. I resoldered it, but nothing changed. The insulation of the wires from the pickup melts very easily when the wire heats up so it seems possible that two of the wires inside the pickup's multicore came to touch when I gripped it lightly with a pliers at the start of the wiring. Does anyone know if this problem would be consistent with the live signal running to ground in one of the pickup wires? Failing that, I'm all out of ideas, so if any one has any thoughts regarding the cause or anything that would help me further diagnose the cause, I'd appreciate it.

I won't get into town for quite a few days, and I'd prefer to fix this myself, so I'm not interested in hearing that such and such in whatever music shop can fix everything cause he's the man etc.

Cheers,
Eoin

Doctor J

I would say try things step by step. Wire each pickup onto the input jack separately (no pots, just a pure signal to and from the pickups) and see if the buzz is there. Then try them with the old pots and electronics (if you haven't de-soldered them).

Is it the same kind of buzzing/humming if you were to put the live instrument near a television, for example?

Googe

You should try john in musicians inc cause hes the man.

Eoin Madsen

Originally posted by Doctor J
I would say try things step by step. Wire each pickup onto the input jack separately (no pots, just a pure signal to and from the pickups) and see if the buzz is there. Then try them with the old pots and electronics (if you haven't de-soldered them).

Is it the same kind of buzzing/humming if you were to put the live instrument near a television, for example?

Thanks for the reply Dr J. I finally got around to trying that today. I used the old jack to check the new pickups individually. Both pickups make the humming, though the bridge pickup noise seems to be louder. When the ground on the jack is not connected to the copper shielding and bridge the whole thing buzzes very loudly all the time - and when I touch the shield or bridge it gets louder. Once they're touching it's not too bad, but we're back to square one. The neck pickup has shielding around and beneath it, but the bridge pickup (not under the scratch plate) has no copper shielding. When the signal touches ground it just reduces the signal strength or cuts the signal (and ditto for the other wires in the pickup multicore) so I'm thinking that's not the problem after all. Any other ideas based on this info?

Doctor J

If you wire them into a jack, not even in the bass, just wire one of the pickups to a jack (or just hold the wires onto the tip of a lead, are you getting the buzzing then? Do you get the same buzz from the old pickups?

Eoin Madsen

Yeah, I still get the buzzing when the pickups are out. Curiously enough, it's louder in general but reduces when I touch the earth of the jack to the shield in the bass guitar. I've also observed that the buzz (that comes and goes when I touch the earth) reduced very significantly when the volume pots are down just a little. I haven't checked the original pickups, I'll do that later and let you know.

Eoin Madsen

Yeah, the old pickups do it too. I'm left with the conclusion that I'm listening too hard, my house is broken, or everything I touch breaks.

feylya

<stock reply> Try a different cable/amp</stock reply>

I know it's obvious but it's all I can think of at the moment.

Eoin Madsen

It'd be funny if it was just a dodgy lead after all that... But unfortunately I tried all that - as seen in my original rant.

feylya

Have you tried a different bass through the amp?

Eoin Madsen

I haven't noticed the problem with any other basses that have been played into it, or the mixing desk. But that said, I may not have been listening this hard.

Doctor J

Just how loud is the buzz? Every pickup will make noise, single coils more than humbuckers. Are the old pickups making the same amount of noise as the new ones?

Eoin Madsen

It's hard to tell without reproducing the exact circumstances. They buzz more when out of the bass than in it. Buzz I would expect alright - what seems strange is that it lessens when I touch it. To me, it implies that it's a problem that could be fixed.

As I said, it may be that I'm listening too hard at this stage.