Buzzing Gets Louder When Touching Pickup Height Screws

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by x8915, Mar 29, 2015.

  1. x8915

    x8915 Member

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    Hey guys. I have a Warmoth strat build. It's rear routed and the pickups are mounted using black metal mounting rings. I believe I have shielded the cavities correctly. The humming is bearable when I'm not playing but when I touch the pickup height screws the hum/buzz gets way louder. Any ideas what the issue could be? Are there some kind of non conductive screws I could use or something? Thanks in advance!
     
  2. walterw

    walterw Gold Supporting Member

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    what kind of pickups?

    ideally, those screws should be grounded like all the other metal on the guitar, so that touching them doesn't make noise.
     
  3. Tone_Terrific

    Tone_Terrific Member

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    Meter it.
    or...Run a jumper wire from a known ground as a test.
     
  4. x8915

    x8915 Member

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    They are Lollar S Specials. I've tried the jumper wire from a known ground and there was no change.
     
  5. Tone_Terrific

    Tone_Terrific Member

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    That means the guitar should be loudly buzzing any time you touch a grounded spot and that would include the strings.
    Something else is going on.
     
  6. bluesjunior

    bluesjunior Member

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    Have you checked the jack?. A few years back I bought a new switchcraft jack socket for a guitar. At the time I was quite new to soldering etc and just soldered the wires onto the new socket as they were on the old. Couldn't understand why the guitar played ok but was buzzy and noisy as heck when I touched the pickups etc. When I got right down to it, I found that on the old cheapo jack although they looked the same the inner and outer rings were opposite. A quick swap over and a resolder solved it but I never take anything for granted now.
     
  7. John Coloccia

    John Coloccia Cold Supporting Member

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    I'd personally be interested in knowing the resistance between the screws and ground (the output jack, for example, or some other convenient piece of metal). What you're describing is ground loop kind of activity. Is the pick guard shielded? How does that shield connect to ground?
     
  8. walterw

    walterw Gold Supporting Member

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    so construction-wise, regular strat pickups. fiber bobbins, no connection to the screw either way.

    respectfully, i'm skeptical that you actually connected those screws to actual ground; if you did, the noise wouldn't be there, or it would also be everywhere else you touched metal, like the strings.

    now that i think about it though, regular strat pickup screws don't make it to ground anyway! the pickup doesn't provide a path unless there's a metal bottom plate, and any shielding under the pickguard is usually gonna miss the screw.
     
  9. John Coloccia

    John Coloccia Cold Supporting Member

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    I'm thinking if the pick guard is shielded, and the shield is very poorly connected (like if it wasn't intentionally connected and is just making incidental contact with a stray piece of shielding from the body), the screw can touch the spring, and the spring can touch the shielding. Long shot, but I don't know how else the screw would matter.
     
  10. AdmiralB

    AdmiralB Silver Supporting Member

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    Um, he said rear routed and metal rings...I'm thinking no pickguard.

    I'm guessing there's a mixup between hot and ground on at least one pickup, maybe the wire wraps on the 'flange' are in contact with shielding paint in the pickup cavities, something like that.
     
  11. walterw

    walterw Gold Supporting Member

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    ...aaand the rest of us fail reading comprehension :jo

    i bet the shielding inside the cavities and the metal pickup rings :jo :jo aren't actually grounded.
     
  12. John Coloccia

    John Coloccia Cold Supporting Member

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    Ha ha...good call. :)
     
  13. Mark Robinson

    Mark Robinson Member

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    I would check the soldering first. Look at the volume knob. Do you have a clean grounding connection between the counterclockwise most terminal and the pot case? Is the pot case then grounded thru to the guitar jack somewhere?

    With the Lollars, the black wires are all generally grounded to the volume pot in a stock wiring scenario. As Walter said, the screws must be picking up continuity or inductive noise making ability, somehow other than going thru the fiberboard pick up bases. Throw up a picture if you can?

    Lots of wiring diagrams on the net don't show grounding thoroughly, and just use the ground symbol. I think the metal pickup surrounds would benefit from grounding as others have stated.
     
  14. x8915

    x8915 Member

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    Thanks a lot everyone. I'm a newb when it comes to soldering and making sure everything is grounded correctly. But to be clear, I should connect all the shielding in each pickup cavity to a ground?
     
  15. aussie_owner

    aussie_owner Member

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    I had a similar problem on a used PRS I bought. It turned out that the hot and ground on the pickups was swapped. Similar setup, no pickguard, plastic mounting rings.
     
  16. x8915

    x8915 Member

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    I grounded the shielding in each pickup cavity. Ugly soldering job but problem solved.
     
  17. walterw

    walterw Gold Supporting Member

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    Any shielding that's not grounded becomes an antenna and actually adds noise.
     

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