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track down a ground problem

Discussion in 'Pickups & Electronics [BG]' started by Gintaras, Dec 17, 2006.


  1. Gintaras

    Gintaras

    Dec 11, 2004
    Kent Island, Md.
    Just picked up a Kelly Club fretless 4 and it hums and when I touch the amp head it stops. Tried it with different amps and the same thing. Contacted Kelly and they said it was a ground problem but they never had this problem before.

    Everything seems to be intact. I did remove the preamp from the body and there is a copper shield over one side of the preamp. If I press on it then the hum stops.
    How do track down a grounding problem? I do have a digital multimeter but have no idea what I should be testing and the values I should get :crying: :meh:
     
  2. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Sounds like the older pcb pre's - pretty prone to failure in my limited experience with them - 2 for 2 as a matter of fact.

    So does stopping the hum also stop the sound - ie. short the pre out?

    Hard to imagine any manufacturer never having a ground issue in one of their basses.

    Could be lots of things. The meter is only good for testing continuity - little value for the pre. I'm told an oscilloscope can be used on the pre.

    This thread may be useful


    http://www.talkbass.com/forum/showthread.php?t=276127


    Not much but best I can do cause it could be anything - and bought you some time with a bump.
     
  3. Gintaras

    Gintaras

    Dec 11, 2004
    Kent Island, Md.
    the hum stops and bass still plays :meh:
     
  4. ldervish

    ldervish

    May 22, 2005
    Johnson City, TN
    Can you temp rig a wire from a known ground (e.g. the output jack gnd) to the pre's copper shield to see if that stops the hum?
     

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