Guitar pickup hum

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Russell.Whaley
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2008/02/04 00:32:09 (permalink)

Guitar pickup hum

Just looking for some ideas...

My faithful Epiphone LP-100 (cheap, but it's been a real trooper for a decade) has developed a 60Hz hum that will go away if I keep my hand on the strings. My first thought is that this is related to the pickups.

I've verified that it's not: the instrument cord, the Audio Dock on my EMU 1820m, the compact flourescent lights in my office, or the space aliens living next door to me (well, maybe not that last bit). It is definitely something to do with the guitar.

My sense is that this is a grounding issue.

So... should I be thinking of replacing the pickups, the selector switch, both? Or something else? The pots for volume and tone seem to be fine.

Thanks for the advice...

Russ




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    ew
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    RE: Guitar pickup hum 2008/02/04 02:03:14 (permalink)
    Check your internal grounding. Better yet, shield both the pickup cavities and the control cavities properly. Connect your ground to that, and disconnect the string ground.

    The reason why it quiets down when you touch the strings is that there's a wire running from the bridge or tailpiece to ground, thus using your body as a shield. It's called a string ground. It's a cheap way of shielding, and it also can be fatal under the right(or should I say wrong) conditions.

    So, do a proper job of shielding and grounding and disconnect the string ground. It might literally save your life.

    ew
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    mwd
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    RE: Guitar pickup hum 2008/02/04 11:27:57 (permalink)
    Before being convinced it is the guitar... are you plugging your gear into the same AC outlet that gave you quiet operations before?

    I would make sure your outlet is grounded with correct polarity.

    I live in an old house and had wiring work done on my studio room. I am refinishing the wood floors in the studio so my gear is temporarily on my kitchen table. The same gear that is stone silent in my studio has a buzz like you mention when plugged into my kitchen outlets.

    I can also promise in my case it has nothing to do with the guitar which has noiseless pickups and is shielded out the yeng-yang.

    #3
    krizrox
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    RE: Guitar pickup hum 2008/02/04 13:49:26 (permalink)
    I would check for simple stuff first. Look inside the control cavity and make sure that all the wires are still soldered properly (including the output jack). I've seen plenty of guitars where wires just seem to break loose for no reason whatsoever (perhaps bad soldering in the first place). Replace the filter caps - those are usually easy and cheap to replace. After that, I don't know. You can start by disconnecting the pickups and running them straight to the output jack and see if the problem goes away (you're trying to isolate to a specific component).

    Good luck!

    PS - do you get the same results when plugging into a guitar amp? In another location?

    Larry Kriz
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    Russell.Whaley
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    RE: Guitar pickup hum 2008/02/04 20:48:05 (permalink)
    Thanks, guys -- you've offered a few things I'd never considered... particularly that grounding cheap-out. I'll definitely be looking into that.

    The hum is something that's shown up all of a sudden, so time to pull a few covers and look inside (house wiring and guitar).

    Thanks again! Much appreciated. I'll report back when I get a moment, so that others can benefit from my discoveries, if there are any.





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    LixiSoft
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    RE: Guitar pickup hum 2008/02/04 21:37:29 (permalink)


    Check ground wire to bridge inside the internal cavity.

    LixiSoft
    #6
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