P Bass Humming after new pickups and controls

Discussion in 'Pickups & Electronics [BG]' started by takdriver, Apr 19, 2012.

  1. takdriver

    takdriver Guest

    Apr 15, 2012
    Newbie here. My Mexican P Bass didn't have any issues with humming to start with. I replaced my stock pickups with SD SPB-2's and Both pots, switch and jack with a CTS, Orange Drop and Switchcraft kit. I noticed that there was a humming when I tried playing it. Whenever I touched the bridge the hum went away. I have it wired exactly like the Setmour Duncan diagram. Originally there was a terminal screwed to the wood touching some graphite looking paint which is wired to the volume pot housing. I never put that wire in since Seymour Duncan's diagram didn't show it. Is this why it's humming? I don't have any other shielding in the cavities. no foil on bottom of pick guard or inside pockets of pickups or control cavity. Please advise guys.
  2. guroove


    Oct 13, 2009
    Buffalo, NY
    I'd put that wire back and see if that fixes it. What you are describing sounds exactly like a grounding issue.
  3. Sounds like you have a grounding issue somewhere. Double check your wiring and make sure all of your grounds are there. As long as you have everything grounded and a ground wire going to the bridge you shouldn't need the screw in the body, but if it helps then put it back.
  4. kraigo


    Jun 21, 2007
    Minneapolis, MN
    It's a lot easier if you have a multimeter. Verify the bridge is grounded.

    FWIW, there are a lot of good tutorials on shielding on the web. Guitarnuts.com is one of them. I have a stained glass shop a mile from my house so I just buy a 12"x12" sheet of coper foil from them. If you do that, make sure that it's NOT the black back stuff. The adhesive on that doesn't conduct. The non black back foil sheets have an adhesive that conducts. It makes life a lot easier.

    I don't know how much shielding a P-Bass really helps. The pickup is humbucking, which takes care of a lot of the hum. Grounding the bridge takes care of a lot more. I still shield all my basses.

  5. takdriver

    takdriver Guest

    Apr 15, 2012
    I just ran a multi-meter on it and the bridge ground is solid.
  6. Flabass


    Aug 11, 2008
    St. Petersburg
    I had the same problem when I installed a SD Qtr Pounder in my P. Turned out to be a bad solder point. Fixed that and no more hummmmmmm. I also shielded the entire cavity.
  7. Flabass


    Aug 11, 2008
    St. Petersburg
    +1 on the foil tape. Got mine from Stew Mac.

  8. M.Mannix3


    Jun 12, 2010
    I think it's probably a grounding issue.

    I would check all of your ground connections for a cold solder joint and also I would put that screw back in.

    Maybe is your P pickup wired out-of-phase so it's not humbucking? This shouldn't have happened if you followed the diagram but, just check to see that the connection between the two coils of the pickup connect from the south/negative end of the E and A string coil to the north/positive end of the D and G string coil.

    EDIT: Also, copper foil tape is never a bad idea
  9. CapnSev


    Aug 19, 2006
    Coeur d'Alene
    The screw that you didn't re-connect the wire to was the ground to the body shielding. Fender sprays a shielding paint on the inside of the body cavity, so you shouldn't need foil on top of that. Try re-connecting the screw.
  10. takdriver

    takdriver Guest

    Apr 15, 2012
    So if I don't have that shielding connected to ground it will hum?
  11. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician - Retired

    If you don't have the shielding connected to ground, you don't have any shielding. Shielding works by shunting noise to ground. No ground = no shield.
  12. takdriver

    takdriver Guest

    Apr 15, 2012
    Hey guys. I connected the wire from the volume pot ground to the terminal on the wood and the humming went away. What a difference the conductive shielding paint makes! The bass is pefrectly quiet. It's so quiet I thought my tuner pedal was in bypass at first. Thanks for all the help!