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Fender jazz wiring problem: tone knob controls volume

Discussion in 'Pickups & Electronics [BG]' started by bassman_al, Jan 16, 2012.


  1. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    Hi all,
    First, a search did not get what I needed. So here is my problem:

    while working on a friend's bass, I was taking it for a spin and discovered that the tone knob cuts volume on both pickups. not completely, but very close to it. So tone knob wide open = full volume. When tone knob is rolled off the volume goes way down. To almost nothing when tone knob is turned all the way down.

    A cursory exam under the hood revealed nothing to my non-expert eyes.

    This is a late 90's Fender USA 5-string Jazz bass, with no apparent mods to the electronics that I can tell.

    I can take pics if necessary, but wondering if there is a quick explanation that someone might have.

    Volume pots for both pups work fine. jack has a little crackle to it when the cable is moved around.

    Thanks guys!
     
  2. Thumpin_P

    Thumpin_P

    Nov 26, 2006
    Limestone, TN
    Use a volt meter, check continuity on just the capacitor. Desolder the cap, and check. If you have continuity, the cap is bad. At that point, it is only a piece of wire. Get a new cap, and it should be fine. I ran into the same problem with a Squier P-bass.

    Good Luck!
     
  3. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    So it might just be a cap replacement and not a pot and cap replacement?
     
  4. Thumpin_P

    Thumpin_P

    Nov 26, 2006
    Limestone, TN
    Right! Inside the capacitor, the contacts are not supposed to meet. When one goes bad (gets burned out) the contacts meet, changing it from a capacitor, to basically, a piece of wire. At that point, everything gets shorted to ground...acting like a volume control.
     
  5. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    I just read the potentiometer and capacitor articles on Wikipedia so I think I understand what you are saying. And it makes. I'll give it a shot! Any particular size capacitor you suggest? A friend has a .040 that he is going to sell me. He lines that size
     
  6. Thumpin_P

    Thumpin_P

    Nov 26, 2006
    Limestone, TN
    I believe that .040 will work. Depending on the size of cap you use, it bleeds more or less treble off. I have seen them anywhere from .040 all the way up to .100. If your friend feels that there is too much treble, when rolling off the tone control, just look for a higher value. Good luck!
     
  7. Thumpin_P

    Thumpin_P

    Nov 26, 2006
    Limestone, TN
    Oh, and check the solder connections on the jack. They may need to be touched up a little. Either that, or the contact itself (the leaf that actually contacts the plug) may be sprung back too far. If that is the case, simply bend it back in place.
     
  8. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    Thanks! I've actually dine that bend repair before on my MIM. I'll check the solder connections as well. Thanks so much for the help!
     
  9. Thumpin_P

    Thumpin_P

    Nov 26, 2006
    Limestone, TN
    Anytime! Glad I had some knowledge...It's good to help people out!
     
  10. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    Does it matter which lead on the cap connects to ground and which connects to pot?
     
  11. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    No.
     
  12. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    Thanks!
     
  13. jayhoward

    jayhoward

    Jun 26, 2011
    Did this problem ever get solved? I'm having a similar problem on my MIM Jazz.
     
  14. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    Solder problem was the correct diagnosis. A wire was not connected. I soldered to diagram spec and it now works perfectly. One wire on the input jack had come loose and was no longer soldered.
     
  15. Thumpin_P

    Thumpin_P

    Nov 26, 2006
    Limestone, TN
    Glad you got it cleared up.
     
  16. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    I did replace the cap first. Did not fix the problem but good to get the experience making the repair. The solution ultimately was to fix the jack.
     
  17. Thumpin_P

    Thumpin_P

    Nov 26, 2006
    Limestone, TN
    Cool! Good outlook, too!
     
  18. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    Thanks!
     
  19. jayhoward

    jayhoward

    Jun 26, 2011
    Turns out mine was a bad pickup, and it's good now. Glad you got yours fixed, too.
     

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