Static hum in certain positions Tele

[frets]

Hi Guys😸😸😸

I have a customer who installed one of my harnesses, a Tele with phase reverse, pretty straight forward. He’s a getting a shrill hum in positions 1 and 4 when he touches the pickup. Only when he touches a pickup does this hum happen. It almost sounds like a loud static. He does not have this effect in positions 2 and 4. The 4-way is wired Neck, Neck + Bridge, Neck x Bridge, Bridge. So this static noise is happening when the pickups are selected on their own. No other hum is reported; e.g., touching the knobs.

Any thoughts on what the problem may be?

[gckelloch]

Off hand, it sounds like the leads are switched at the output jack, and the hum gets cancelled when the pickups are OoP. Is the ground wire for the OoP pickup chassis separated from the neg lead?

[sumgai]

I'm going to assume that you meant positions 2 and 3 are problem-free, and 1 and 4 (the single pups by themselves) are where the problem occurs, yes?

Is this customer playing with any additional effects pedals, such as perhaps a gain or a boost of some kind? Or is he getting this while playing straight to the amp?

When you say "my harness", are you including the pickups with that, or is the wiring harness made up of controls only, meant to be installed with pickups he obtained from elsewhere? Reason I ask is it sounds like the pups are slightly microphonic, where touching them sets them off, so to speak. (Provided he's not using some kind of effects pedal between the guitar and amp.)

HTH



sumgai

[frets]

Sumgai,
I’m sorry, Yes, positions 1 and 4 are the problematic positions. He is not running any effects. The harness is a phase reversal harness I built (Volume/Phase to Neck, tone,4-way). Before posting here, I did tell him to check his wiring for a miswired jack and the phase wiring on the push pull. He has checked those and they are fine. So the problem remains. Beyond checking for reversed wires, I am at a loss for any other recommendations. I know I wired it correctly because I test everything I make. I did not provide the pickups. It is a strange static sound, I’ve never quite heard anything like it. I would not call it microphonic.

[newey]

Does the noise change at the neck pickup if the phase switch is pulled?

[mikecg]

Maybe the customer is sitting on top of a switching power supply, a malfunctioning fluorescent light, or a powerful wifi  router?

High frequency (EM) interference can come from a number of domestic and industrial sources.

[mikecg]

And I am wondering where your customer has connected his pickup shield wires?

[sumgai]

OK, they're his pickups, and the pickups themselves are most likely the problem. Let's go down a standard troubleshooting path, shall we?

As noted by mikecg, start with the environment. The easiest thing to do is move to another location. Best is another house, or at least somewhere that the same circuit is not in use. Another room might be OK, if it's on a different circuit... but that's still not as good as going elsewhere. A friend's home, a local pub or coffee house, even just outdoors, all are better than another room in the same house.

An alternative would to bring another guitar into the equation. Either the customer has another axe to test with, or else a buddy should bring his guitar over and test with the same cable and same amp, in the exact same setting (position in the room, knobs dialed in the same way, etc.). This is also cheap, but guitar-playing friends might be unavailable for this purpose in a reasonable time frame - we all know how this goes.

Next step: Test the pickups all by themselves. This means removing your control harness and just plugging the pickups straight into the amp. Much more difficult, and not a one-minute task, but at least it's still cheap. At this point, either the problem persists, and it's the pickups, or else the pups make no noise when "out of the guitar", and that means that he has a bad wiring job. And here, I'm presuming that you test everything before it leaves your factory, am I not correct?  Conversely, have him hook your control harness to another set of pickups and see what happens.

This just about covers all the bases. What we've done here was to implement the old Rule Number One of troubleshooting  - Substitute With A Known Good Part.  Not always the easiest or cheapest way, but when done in a logical manner, it gets the job done.

It still could be other stuff, once we've eliminated the easy things. The body itself may have a resonance, but that's highly unlikely to affect both pickups. The body may have a shielded cavity, and somehow a short is occurring after his final assembly. Again, very unlikely, but we all know how Mr. Murphy works, don't we.

If he hasn't sorted it out in a day or two, we'll need to see pictures. 

HTH





sumgai

[frets]

Thanks Sumgai et. al.,

He has his ground wires for the pickups, including the neck cover, running to ground on the back of the volume. He does get the hum when the push pull is activated (pulled up).

I have asked him to send pics.

[unreg]

ground for pickups == signal
ground for neck cover == shield?

back of vol pot != jack’s ground?

[sumgai]

frets,


unreg's correct, you've got to (gently) pin this guy down for a more specific meaning of "ground goes to....". But perhaps with pictures we'll see what's what.







sumgai

[frets]

Sumgai,😸
Yeah, I know. I really think he has some wires backwards but I’ve not heard from him so maybe he’s fixed it. You only hear from them when there is a problem.