Noisy jazz bass ...pickups to blame for?- created 05-07-2011

Escalante, Andrés - 05/07/2011.13:04:39

Hello everyone, a few months ago, I wired up a nice 70s jazz bass with newly rewound pickups. I carefully shielded the control cavity and wired the star grounding and shield grounding separately. The result was quite neat, with very low noise ...for a while. My client told me he left the bass unused for about two weeks, and when he plugged it back, it started making a loud hum, unless you touch the strings. I checked every conection and everything looks fine. What I observed, is whenever you touch the pole pieces, it makes a very loud buzz; the noise increases even if you get your fingers near the magnets. Are the pickups the main responsible for this issue? Should they be shielded somehow? Thanks in advance for your help

It sounds like the windings have become shorted to the magnets, which is not a good thing. The only cure is to re-wind them, and put a layer of tape around the magnets first

I'd agree with Mark's prognosis, but just a couple of questions... is it happening with both pickups or just one? And when you say "everything looks fine" did you also check it with a multimeter or some some of continuity tester?

Before breaking into the pickups I'd be tempted to wire each of them directly to the output jack to isolate whether it is the pickups and which one of them is causing the problem because it would unlikely (but not impossible) for both of them to suffer the same problem.

You can check to see if the coil is shorted to the magnets with an Ohm meter. Just check each magnet to each lead. You could read infinite ohms

If you didn't put tape over the magnets or spray them with something really tough then you probably have a short as noted by everyone above.

You should always try to ground your magnets and shield all your coils regardless.

Thanks a lot for the input. Dave, actually, the neck pickup mmakes more noise than the bridge one. Since both of them were rewound by the same person (I don't remember who was), it's not surprising both of them have the same problem.

A good pickup man should stand behind his work and fix it for free

Andrés,

Lastly, double check that you didn't reverse the hot and the ground wires at the jack. I doubt it but it's one way to get lots of noise and something to check before you blame the pickup winder.

Jazz basses are noisy, it's part of their charm I guess.

Bah!, I was wrong about the poles in the last post, Ignore that.

The other confusion is that our dear planet's North pole is actually a South up. (It took me a long time and a lot of cajoling from others to finally believe this.)

<i>The other confusion is that our dear planet's North pole is actually a South up. </i>

Please explain.

Barry, the North pole is actually a South pole i.e. the North poles of magnets seek it

Thenks for the info Dave. I've checked the magnet polarity and the reverse winding, and it was fine. I've noticed similar cases even on guitars with humbuckers (those really cheap ones). It seems the customer will have to send the pickups back and have them fixed. The work should be guaranteed, especially on those vintage Js

Even if the windings are not shorted to the magnets, it is common for the magnets to not be grounded, and thus touching them induces noise into the pickups. They should be grounded.

All you need to do is scrape any lacquer or wax off the bottom of the magnets, and stick some copper foil tape, the kind that has conductive adhesive to the bottom of the magnets, and run a ground wire to the tape.

That should fix the problem. I did this recently to a Fender P/J bass that I was installing one of my humbucking jazz pickups into, and then P was noisy. This made it very quiet.