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Static when moving down strings

Discussion in 'Pickups & Electronics [BG]' started by SBassman, Jan 10, 2006.


  1. SBassman

    SBassman

    Jun 8, 2003
    Northeast, US
    Some of you helped someone try to debug an electrical problem recently, so I thought maybe you could help me.

    I have an Landing bass - that I don't use - because - there's some electrical problem.

    It's a passive bass with EMG humbuckers. When I slide my fingers up and down the fretboard, I get a static sound.
    I also get it when I touch the knobs, which are gold.

    Can anyone walk me through debugging it? Thanks.
     
  2. SBassman

    SBassman

    Jun 8, 2003
    Northeast, US
    Actually, it's not from moving fingers up and down the board.
    It's when I occasionally slide my Right hand - thumb specifically - anchored against the front pickup.

    Bottom line is I can now reproduce it super easily by sliding a finger along the edge of the pickup. That's what is producing the static.

    Any help debugging it would be appreciated.
     
  3. that's a sign that your bass is about to EXPLODE!

    RUN!!!!



    seriously, now...
    take some photos of your control cavity ....let's have a look inside...

    have you investigated your shielding and grounding yet?
     
  4. SBassman

    SBassman

    Jun 8, 2003
    Northeast, US
    I wish I could. Our digital camera recently died.

    I have a gig this Saturday. Maybe I can open up the cavity right at our gig and have someone else shoot it.

    I have not investigated grounding yet. How do I?

    Also, more info:

    The bass is giving off a perpetual hum which stops when I touch the - gold - volume or tone knobs.

    ?

    Thanks.
     
  5. SBassman

    SBassman

    Jun 8, 2003
    Northeast, US
    More info:

    I opened the cavity. It looks Extremely clean and well done.
    I don't think anything is loose in there.

    Precise model of pickups: EMG 40HZ passives.

    Isn't there supposed to be grounding to the bridge?
    I don't see any means for this. I don't think this is something that broke - I don't think it ever had it. Shouldn't I see a hole in the cavity specifically for the grounding wire to the bridge?

    While holding the bass, touching the gold volume or tone knob makes the bass dead quiet and sounding sweet.
    No more hum, no more static if I brush across the pickup.

    I also tried touching a wire from the bridge to various places inside the cavity. At times, it lowered the hum but
    did not eliminate it like when I touch the knobs.

    This certainly smells fixable. I hope somebody can help. Thank you.
     
  6. ehque

    ehque

    Jan 8, 2006
    Singapore
    connect the bridge to the star ground point, or a control knob casing if you dont have a star ground. then, *touch* the strings. this should ground yourself (thru the strings, bridge, casing, jack ground) and should kill the hum. when you play, you are most likely touching the strings anyway (like how guitarists kill hum)

    try that? human bodies are pretty good at picking up electromagnetic interference. grounding yourself will put your body at ground, reducing the EM coming off you.

    shielding the cavity properly also helps.

    see if this helps you. and double check the wiring, some people have gotten shocked doing this wrongly.
     
  7. ehque

    ehque

    Jan 8, 2006
    Singapore
    sorry for the consecutive posts, but i dont see an edit button.

    just wanted to add that if this works for you, you gotta remove the bridge, then drill a hole from under the bridge away from the screw holes into the control cavity. be extra careful there.
     
  8. Gianni

    Gianni

    Jul 4, 2001
    Palermo - Italia
    Hello, I have submitted this question elsewhere, I try also here hoping to find an answer.

    I have a similar problem on a G&L1500, in which the original preamp was exchanged with a Seymour Duncan STC3p, and on a G&L2000 with its original preamp.

    In particular I hear a tiny scratch when the string touches a fret, particularly if I simultaneously touch the fret with a finger.
    The same noise is produced when I touch and/or move one of the tone pots in the 1500 and anyone of the pots in the 2000.

    In the 2000 the noise remains also if I shut down the preamp, bypassing it and disconnecting the battery.

    My impression is that this problem arised abruptly some months ago for the 1500 and some days ago for the 2000.
    I can say that I have noticed it in the 2000 after having rewired one of the 2 serial-parallel-single coil switches I installed years ago, but I am not sure that the problem is due to this operation, taking also into account that the switch works properly...

    What I have noticed today, after some tweaking, is that the noise disappears if I touch the bridge with one hand.
    Precisely: if I make the string to touch the fret using a finger of the left hand, while I touch the fret with another finger, the tiny scratch happens; if I am touching the bridge with right hand, the scratch does not happen.
    The scratches are higher if I am insulated from the ground.


    I have not tried to use the basses outside my home, or with some device using batteries, in order to be sure that it is not something regarding electrical power in my home...

    Ciao!!
    Gianni
     
  9. SBassman

    SBassman

    Jun 8, 2003
    Northeast, US
    Wow. If that's the fix, it's going to be scary. This is a beautiful, one of a kind bass that I can not mess up. :eek:

    Thanks for the help. I'll be trying the test in a little while.