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Humbuckers still hum

Discussion in 'Pickups & Electronics [BG]' started by uly_, Aug 1, 2007.


  1. uly_

    uly_

    Jul 4, 2005
    Denmark
    Hiya Talkbass,

    First of all: I have done a search, but didn't really find anything useful (might have missed something, somewhere though)

    Anyway, I have installed a set of DiMarzio Model J humbucker jazz bass pickups and everything is wired just as it should, I have checked and double checked a few times. I have even got it checked by two experts at the local shops, but they couldn't help me out :(

    It's wired like a standard american jazz bass and I've followed DiMarzios instructions when installing the pickups.

    Here's the schematic I used from fender.com:
    http://www.fender.com/support/diagrams/pdf_temp1/basses/0193400_02A/SD0193400_02APg2.pdf

    However, there's a wire connected that's not shown on the schematic. It's this one:
    [​IMG]
    Could that be the sinner?

    The noise is there when I don't touch any metal parts on the bass. I do know that it's a grounding problem, and yes, there's a wire going to the bridge from the back of the tone pot.

    Any ideas what to try out here? :confused: Is there any way that I can locate which ground that's not working?

    Thanks in advance, and sorry for bad english :(
     
  2. TrooperFarva

    TrooperFarva

    Nov 25, 2004
    New City, NY
    That wire would connect the ground side of the instrument cable to the ground on the instrument. I know that on active instruments, the ground wire of the battery is connected through the ground side of the instrument cable, but based on the fender diagram, it seems as though they don't want the grounds connected. I say cut the wire, it could fix the problem, and if it doesn't, it's 2 inches of wire, it'll take a minute to replace it.
     
  3. uly_

    uly_

    Jul 4, 2005
    Denmark
    Thx for your reply :) Sure, I could try to disconnect it, will do that tomorrow!

    I came to think about something: should there be those .. don't know what they're called.. so I will post a pic instead :D

    48967103.

    .. should they be between every pot and the control-plate? Because I can't remember if one of the pots has got such a thing on it. Does that have anything to do with grounding?
     
  4. TrooperFarva

    TrooperFarva

    Nov 25, 2004
    New City, NY
    Not really, that's just a lock washer, so that when you tighten the nut down on the pot shaft, the pot will stay in place. The lock washer just prevents the pot from moving, and the nut loosening as a result.
     
  5. uly_

    uly_

    Jul 4, 2005
    Denmark
    Nevermind, that was a dumb question :D

    Well I will try to cut that wire tomorrow to see if that helps. If it dosn't, I don't know what to do since everything seems to be right :(
     
  6. tadawson

    tadawson

    Aug 24, 2005
    Lewisville, TX
    The jack is grounding via the control plate, and the lockwasher is there to ensure a good contact. That makes the wire redundant, so I doubt it can change anything for the better to remove it - if anything, I suspect things may get worse, since grounding via the plate and pot shafts is, IMHO, much more prone to flakiness . . .

    Since you did not detail your wiring of the DiMarzios, I assume that you wired those as per DiMarzio's directions - red to the pot center terminal, green to the pot can, and the black and white get joined together at the pickup? If not, then you may not have the hum coils wired in correctly, giving your problem . . . . if so, then I am at a loss . . .

    - Tim
     
  7. uly_

    uly_

    Jul 4, 2005
    Denmark
    Tim:
    Yes I've wired it after DiMarzio's direction and everything should be fine, i've checked the wiring many times now to be sure I didn't screw up somewhere.

    I'll have to see if there's missing any of the lockwashers, can't remember if I skipped one/some of them when I installed the pots again.
     
  8. basadam

    basadam

    Nov 29, 2005
    a) This may be a shielding issue. DiMarzios cancel 50/60 cycle hum but not interference. Is your bass shielded?

    b) (highly unlikely) Once I had a similar problem (DiMarzios and perfectly shielded bass), it turned out the ground wire on the mains outlet where I connected my amp was loose.
     
  9. kipsus

    kipsus Physicist

    Sep 18, 2005
    Vilnius, Lithuania
    I had exactly the same problem with exactly the same pickups. You need to shield the thing
     
  10. uly_

    uly_

    Jul 4, 2005
    Denmark
    Hmm, well okay then. How exactly do I shield it? Just by putting some copperfoil inside the control cavity?
     
  11. kipsus

    kipsus Physicist

    Sep 18, 2005
    Vilnius, Lithuania

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