1. #1

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    Hi fellas. I just installed a new wiring harness in my Greco Barney Kessell-style guitar. Being a 2 3/4 inch deep archtop with limited f-holes and PU holes, getting the pots in was a difficult and time-consuming install. I know others have done this so you know what I mean.

    Anyway, at this point, the pickups sound great as long as I have them dialed fully up. But if I start dialing them down, I get a grounding noise. This happens with either pickups. I know it's a grounding problem because if I keep my hand on the strings while dialing down the pots, the noise is significantly minimized. Without my hand on the strings, the grounding noise gets louder the lower I dial the pots.

    I'm wondering if any of you have any thoughts about where my grounding problem might be. I'm hoping (probably against hope), that I can resolve this without taking out the whole harness. Thanks!

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  3. #2

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    Sounds like a bad or no ground connection somewhere.

    OR the harness is wired wrong.

    It may be that you need to remove the harness and check all the connections and pots against the diagram.

    If you could post the schematic it would be helpful.

  4. #3

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    Thanks BBGuitar. I'm afraid that is probably what I'll have to do. I think I'll start by checking the easy to reach parts without taking out the harness: the input jack, selector switches -- but I think ultimately ultimately I'll have to disassemble the whole thing -- AAARGHH!!

  5. #4

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    Are the strings grounded via the tailpiece to the jack?

  6. #5

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    Quote Originally Posted by TedBPhx View Post
    Are the strings grounded via the tailpiece to the jack?
    Thanks for asking. I think so, but that's going to be the first thing I'll check...

  7. #6

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    Ungrounded strings seems a likely culprit. Try running a temporary ground wire between the shield side of your instrument cable and the strings to see if the problem goes away. Or test continuity with an ohmmeter.

    If not, more clues might help:
    What happens to both volume and hum as you roll the volume knobs to 1/2 and nearing zero?
    Do both volume pots act the same?
    To the tone knobs operate correctly across their full range?
    Last edited by KirkP; 05-05-2019 at 06:26 PM.

  8. #7

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    Quote Originally Posted by KirkP View Post
    Ungrounded strings seems a likely culprit. Try running a temporary ground wire between the shield side of your instrument cable and the strings to see if the problem goes away. Or test continuity with an ohmmeter.

    If not, more clues might help:
    What happens to both volume and hum as you roll the volume knobs to 1/2 and nearing zero?
    Do both volume pots act the same?
    To the tone knobs operate correctly across their full range?
    I tried running a temporary ground wire between the input "plug" and the tailpiece. It didn't help. Next, I"ll do it right and pull out the input jack and see if there's a problem there. The volume pots both act the same way with the humming problem; if I have a vol pot set to full (10 on the knob) there's very little humming noise. If I turn it down to around 8 or less, the hum comes loud and clear and stays the same all the way to 1. If I keep either hand on the strings, the humming stops. Meanwhile, the tone knobs operate correctly across their full range.

    Also, I've accessed that I have a faulty PU selector switch. It works fine in neck or bridge positions, but in the middle (where both PUs should be working), only the neck PU works. I've ordered another selector switch and I'll be changing that out as well. I don't know if it has anything to do with the volume pots hum, but either way, I'll be changing it and maybe I'll get lucky!

    One good news is that the PUs sound great. I found an old original black-sticker 50's PAF in my drawer full of goodies! I used it for the neck PU and a Seth Lover for the bridge PU. Both sound great, but the original PAF just kills!

    Funny huh? Some people would give their right arm for one of those PAFs, and I'm using it on a 60's Greco copy of a Gibson Barney Kessel...

  9. #8

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    So when the volume pots are set all the way to minimum you still hear the hum? Do you still hear the pickup signal with the pot set to minimum? If so, it’s probably a bad connection on the grounded side of the pot. But if the pickup signal is totally gone yet you still hear hum, I’m stumped.

  10. #9

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    Quote Originally Posted by KirkP View Post
    So when the volume pots are set all the way to minimum you still hear the hum? Do you still hear the pickup signal with the pot set to minimum? If so, it’s probably a bad connection on the grounded side of the pot. But if the pickup signal is totally gone yet you still hear hum, I’m stumped.
    Thanks KirkP (and TexB and BBGuitar) for helping me sleuth out this hum issue. I'm pretty sure it's a bad ground connection somewhere, but I will wait until I get the replacement toggle switch (separate but possibly related issue). At that time, I'll go in and try to find the culprit. Until then, the guitar works fine with the vol pots all the way up. Since I play the guitar 90 percent of time that way, I can live with the issue until I can get to fixin' it.