J Bass installation and resistance assistance.

Discussion in 'Pickups & Electronics [BG]' started by Camarillo, Feb 20, 2021.


  1. The bridge pickup on my '91 MIM Fender after several come and goes seems to be gone forever.
    Not an expert in electronics here, but last time I bring it to a tech for a professional setup he changed the pot. Worked for a while then I lost it again.
    Now, I wasn't so happy with the sound, found it a little weak, then I decided to buy new pickups, and change both. By myself. First time, so be gentle...:help::)
    After some reaserch and demos on youtube I've got a couple of E1 from Epic Custom Shop. Same size, because it's an old MIM, 92mm both. It came packaged with no "label". So I thought "which is which"? Talkbass, google, answer: resistance must be higher on the bridge pickup. Ok, got a multimeter. measured them: same resistance 8,28 K Ohm (I guess..). So I can put any of them anywhere I like. Is that ok?

    Coming to installation, after some reaserch and tutorials, the wiring should be clear. But not completely maybe...
    What is not clear to me is the purpose of the two "pyramids" of soldering tins on the back of the pickups.
    Thank you!

    IMG_1659.JPG
     
  2. dwizum

    dwizum

    Dec 21, 2018
    You can ignore those pyramids of solder. They're the backsides of the eyelets used to solder the magnet wire on the coils to the hookup wires (the black and white wires coming out of the pickup).

    It strikes me as a little unusual that you have two apparently identical pickups. You might want to verify with the manufacturer that they didn't accidentally ship you two of the same pickup. It's common for the bridge to be hotter (and have a higher resistance) but the pair needs to be reverse polarity and reverse wind direction from each other in order to reject noise and still be in phase when played together. If they accidentally shipped you two necks, that won't happen.
     
  3. Thanks! I wrote to the manufacturer.
    In case the polarity should be wrong I would get a strong hum right?
    And what if the polarity should be correct but the resistance equal?
     
  4. dwizum

    dwizum

    Dec 21, 2018
    If they're not reverse wound/polarity from each other, you'll just get normal single coil hum when both pickups are on at full volume, instead of getting hum cancelling. It might not be that bad but it's definitely not ideal.

    And, if they sent you two necks instead of a neck and a bridge, you may find that the bridge pickup sounds weak. Bridges are normally wound hotter since there's less string movement near the bridge end of the string, so the signal is weaker. If the bridge pickup isn't wound hotter, then it will be quiet in comparison to the neck pickup, when switching between the two on full volume.
     
  5. Clear :thumbsup:
     
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  6. Ok then. The manufacturer answered that is normal they have almost the same resistance, but polarity and winding is all right. In fact the magnets attract as they should, I didn't consider that.
    So I did the swap, adjusted the pickup height to compensate volume: nice growl, very little single coil noise, everything is ok except one thing. If I lower both volumes I still have signal output from the tone knob at 100%.
    I don't get silence until the tone pot reaches 0%. What's wrong?

    image.jpg
     
  7. dwizum

    dwizum

    Dec 21, 2018
    At first glance the layout of your controls looks correct. It's really hard to diagnose these problems from a photo. Get a multimeter and start tracing everything to find where the short/miswire is.
     
  8. I have the multimeter. Measured from hot and ground of the connected TS jack I get the almost the same levels I had from bare wires with pickups disconnected, just a little weaker. From the tone knob open (in sounding position) I don’t get any measure.
    I was thinking about this. The old pickup ‘s ground (black cables right?) were soldered to a “plate” under the sponge and then a second black cable started from there reaching the pot.
    I unsoldered the cable but left the plate since is glued under the sponge and I don’t have any other. Could that be the reason? I have copper tape in the pickup s cavity as well...
     
  9. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
    The third leg of the middle potentiometer needs to be grounded, as in this illustration.
    WDUSS2101__39393.1481759758.jpg
     
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  10. Ok I’ll do that.
    It’s funny because that pots, newer than the other ones as you see, it’s been installed by a luthier...
     
  11. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
    I’m sure he’s human.
     
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  12. And that is was the issue! Now everything is working properly. Punchy and silent. Thank you very much for your support!
     
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  13. dwizum

    dwizum

    Dec 21, 2018
    I like my basses just how I like my henchmen...

     
    Camarillo likes this.
  14. :roflmao:
     
  15. Primary

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