locating cuase of buzz/hum.

[Robert Smallwood]

Hi.
I have a hum that is leaving me non-plussed.

I have measured the resistance of all possible pairings - jack, tone, volume, switch, pickup 1, pickup 2 (covers) and always get a zero reading. I have used a common ground for all components ie each ground wire is individually soldered to the 'common ground'.

The hum is probably 'liveable with' ie not intrusive compared to the volume of the guitar, but it is alleviated by touching any of the above mentioned components , so i'm a little perturbed.

Touching the bridge or touching the strings has no effect at all.

Also it seems to dissipate almost disappearing over time when I'm playing the guitar.

If you have some ideas I can test in order to identify the source, please let me know.

Thanks,
Rob.

[Bob Gramann]

Are the wires from the pickups either twisted around each other in their way to the pots or shielded? Are all of the signal wires twisted with ground wires in their paths? Are your control cavities shielded?

[Peter Wilcox]

I have found this article helpful in the past:
https://www.prosoundweb.com/eliminating ... c-guitars/

and especially love this pic.

[Joshua Levin-Epstein]

What kind of pickups are you using? In my experience, whatever that means, a single coil pickup will always hum. Shielded cover, shielded cable, shielded cavity: it will always hum.

If these are humbucking pickups and they are humming, test the pickup itself before or disconnected from the controls etc. Make sure the two coils are "good" (no breaks), are connected properly; series out of phase or parallel out of phase. Try sending the pickup directly to the amplifier, alligator clips to shielded cable to 1/4" plug. The alligator clip that is going to the negative side of the pickup must be connected to the shield, same as the sleeve of the 1/4" plug. If the pickup going to the amp is noisy, the pickup is the source of the hum and nothing short of replacing the pickup will help, unless you are in a noisy room (Transformers, fluorescent lights, etc). Note I am describing testing a single two coil pickup, not the two individual (neck and bridge) pickups.

Now, into the weeds:

If the coils in a properly assembled humbucking pickup are very mismatched, the pickup will hum. Consider a dead coil an extreme mismatch.

If the cable you're using is of poor quality, there will be hum. I tap the cable to see if it is microphonic. If its microphonic, it is discarded.

Do you have a guitar you are certain doesn't hum? If it hums where you're testing, it is the room that is haunting you.

Too much fun.

[Charlie Schultz]

Also see our buzz FAQ, put together by our members: https://www.mimf.com/phpbb/viewtopic.php?f=19&t=6

[Robert Smallwood]

Thanks for the info.
It looks like the earth wire from the bridge to the ground point isn't continuous. I touch a wire from the bridge to the pickup switch and the noise abates.
I am still nonplussed ) as to how this might've happened , bur more so with the prospect of withdrawing a bridge-post and replacing the wire....