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MIM Jazz Bass V Wiring Issue

Discussion in 'Pickups & Electronics [BG]' started by eleven59, Sep 23, 2008.


  1. eleven59

    eleven59

    Mar 6, 2008
    So, I posted a thread a while ago about some issues I'm having with my bass rig, mainly grounding issues, radio interference, etc.

    The radio interference is still an issue, but I'm not sure there's anything I can do about it. We're on the 3rd floor of a building full of storage spaces with really crappy wiring. The interference is there as soon as I plug in the cable from my bass to my amp, even if I unplug my bass from that cable. If there's nothing in the input of the amp, there's no radio. It's really only an issue at the jamspace, anywhere else it's nowhere near as loud, if it's there at all.

    The grounding issues are more worrying. If I'm not touching something metal on my bass, I get a loud buzzing, and when I tap on the metal plate around the knobs I get the occasional loud pop. Also, when using my (crappy, broken) mic for backing vocals, if I touch my bass strings and the mic at the same time, I get a mild shock.

    So I finally got around to opening up the wiring cavity of my bass, and this is what I saw:

    IMG_3570.

    Which looks basically like this wiring diagram, except for one thing: The ground wire on the output jack.

    http://www.lacemusic.com/wiring/pdf/8.pdf

    See, my bass doesn't have that. Should I wire one on there? Would that solve any of these problems?

    Also, I should mention, even with both volume knobs turned all the way down, I can still hear myself playing quietly through my amp (but loud enough that when I point it out to my bandmates, they can hear it too without getting close to my amp).
     
  2. Couple of things:
    1. Yes, there should be a ground wire on the output jack. Otherwise, it is trying to make a ground through the plate - which is probably why you get noise when you tap on it.
    2. I don't see in the picture any ground wire from the bridge - is that missing also? Or is it the black wire on the back of the tone pot? Make sure it is physically connected to the bridge.
     
  3. eleven59

    eleven59

    Mar 6, 2008
    Yeah, the ground wire is attached to the bridge, I can tell because I can ground out the buzz when I touch the strings, which is also why I get electrocuted when I touch my strings and my mic at the same time.
     
  4. Getting shocked is no good. Google around - there are a couple things you can try. Shocks generally come from different grounds between your amp and the PA.
     
  5. ReidK

    ReidK Jst sy n t lsy cmprsn. Supporting Member

    +1 on the ground wire to the jack. That will probably fix most of your issues, possibly inlcuding the RFI.

    If you still get shocked from the mic/bass combo, you either have an amp problem or an outlet wiring problem. (Use a voltmeter to test this rather than your body!)

    I wonder who the genius is at Lace (they should know better) who can't tell an input from an output? :rollno:

    Reid
     
  6. eleven59

    eleven59

    Mar 6, 2008
    Yeah, the shock only happens when using my own mic, which is technically broken off inside the pop screen, and so the wires are probably making contact with the wire mesh of the pop screen :lol: My own fault really, and I don't use it anymore. I'm just concerned about it happening with other mics, since clubs don't always have the best gear.
     
  7. thesteve

    thesteve

    May 28, 2007
    San Diego, CA
    Anyone have any ideas why the jack isn't grounded to a pot? I just opened up my MIA Jazz V and found the same control layout.

    Then I checked Fender's schematic and discovered that this was intentional to the design.
     
  8. Makaio

    Makaio

    Jul 28, 2008
    Looks to me like all the pots are also relying on the connection to the face plate - not just the output jack. This should be fine as long as all the connections are really good which usually requires serrated washers and everything being tightened down real well. This sort of connection scheme is good from a star ground perspective i.e. everything goes directly to one common ground node (in this case the plate) thus eliminating ground loops.. If you do add a ground wire to the output jack, then you might as well have the wire also connect to the backs of all the pots - they can also cause you grief if they are loose. Also, in that noisy environment you might get particularly good results by shielding the inside of the control and pickup cavities with some copper tape - also wired to ground.
     
  9. LaceMusic

    LaceMusic

    Apr 29, 2008
    Artist Relations Lace Music
    I'm sorry Reid, I'm not sure what the issue is with our schematic? Please let me know, and I'll fix it immediately.

    Thanks,
    MikeG
    Lace Music
     
  10. thesteve

    thesteve

    May 28, 2007
    San Diego, CA
    He's saying that in the schematic the jack is labeled as an "input jack", when it should be labeled as an "output jack".
     
  11. I don't think the problem is with the schematic Mike - it looks ok to me. I think it was with the label "input" jack. This should be an "output" jack.

    Edit: Stupid slow fingers :)
     
  12. deepdown

    deepdown Guest

    Aug 9, 2008
    Two basic items:

    Wall A/C testing device & Polarity switches onboard sound reinforcement stuff.
     
  13. LaceMusic

    LaceMusic

    Apr 29, 2008
    Artist Relations Lace Music
    OK, I get it.

    We call it an "input jack" around here. I've have heard it called both myself. I guess because you plug "in" a cable, you can see the confusion.

    Next time we make a diagram, we'll just call it a jack. Or Bill. Or Dave.:)
     

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