Please help me diagnose a possibly bad humbucker

Discussion in 'Just Pickups' started by drmordo, May 30, 2020.

  1. drmordo

    drmordo Tele-Meister

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    I got a used 2-wire Gibson Humbucker off ebay (I think it's a 490R, but the seller wasn't sure), and I'm not sure it's working. It shows 8.5k resistance but it hums when the guitar is plugged in. It also seems like one coil makes sound when I tap it but the other doesn't.

    Are there any other tests I can run?
     
  2. Zepfan

    Zepfan Poster Extraordinaire

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    Sounds like a wiring issue to me. Make sure that the wires to the output jack aren't wired to the wrong lugs(a common mistake) and check all ground joints for loose connection or cold solder joint.

    Could still be a bad pickup, but check all that out first. A pic or 2 could help us see something your not seeing.
     
  3. TimTam

    TimTam Tele-Holic

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    Simplest test of the pickup itself is to connect it direct to the guitar cable using alligator clip test leads.
    [​IMG]
     
  4. radiocaster

    radiocaster Poster Extraordinaire

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    Are you using something metal to tap it?
     
  5. mortron

    mortron TDPRI Member

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    If the pickup has continuity, the 8.5k shows some resistance... Not sure what they're supposed to read.

    My first guess would be grounding. As others said look for physical evidence visually before chasing gremlins you can't see. As a tech, that is always the first step... Sometimes a fix is as simple as a solder or plug connection coming apart.

    After that, multimeter to verify continuity (sometimes things look good but maybe aren't). But do the first and hopefully you come back with some good news.

    Good luck, and don't fret (except while playing), we got you.
     
  6. nathan5782

    nathan5782 Tele-Meister

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    The 8.5K reading sounds be about normal for a 490 pickup, if it's an open cover you could remove the tape and inspect it a little bit more. As somebody else mentioned it sounds like a grounding issue.
     
  7. drmordo

    drmordo Tele-Meister

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    Well, I'm confident that y'all were right about it being a grounding issue, but it has magically disappeared. I suspect the metal cover inside the body cavity was touching something it should not have been. I seem to remember that happening once before on this guitar back in the 90s after I swapped pickups the first time.

    Since you asked for pics...

    Les Paul Custom.jpg

    It's a '78 that I got around '88. The neck pickup went out a few years later, and I replaced it with a Dimarzio Al Dimeola that I never really liked. Maybe 12 years ago I swapped the pickups for Mighty Mite Motherbuckers, which I hated. In the meantime, my SG always seemed to sound better no matter what pickups were in the LP. I recently had the brainstorm to put the same pickups in the LP that are in the SG, which is what I just did (Gibson 490R & 498T). It sounds better than it ever has.

    This was my main guitar for many years. It crossed the country with me a few times and survived numerous onstage hijinks. I remember one solo where I fell backward over a floor monitor mid solo - but kept playing while laying on the monitor. I managed to get back up, but it's a challenge doing a sit-up while playing a 10 pound guitar and no one is holding your feet.

    The pickguard sticker is from a bunch that Chris Cornell threw onstage when Soundgarden played a bar in Pensacola. Why he threw a bunch of stickers onstage I have no idea, but I put it on my guitar to remind me what a great show that was and to inspire my own performances.
     
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