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P bass E/A PU not working but D/G PU works???

B

BassHole1

Oct 29, 2025
385
452
Monterey Bay, CA
#1
I bought a fully loaded working pickguard. Other than soldering the wire coming from under the bridge to the tone pot, I put it in and expected it to play. Aside from the PU being very hot, it sounded like a bad connection and was breaking up (I thought maybe the cable was bad). I went back to clean up a few solders and dropped the height of the PU, and plugged in again (and tested the cable/amp with another bass - both work fine).

The D/G PU bridge side plays and sounds fine. However, I have hardly any volume on the E/A neck side. If I tap on the neck side, I get a tap sound telling me it's connected.

Assume the wiring is correct, any ideas? I have not pulled up the PU's to check the connections underneath. Thanks for any tips/info.
 
#3
WRM said:
Use a multi-meter to measure the resistance on each coil. They should read about the same, but I suspect the EA coil will be either zero (short) or infinity (open). If both are in the same range, there's a wiring problem somewhere.
Click to expand...
I forgot to mention that I did that - the E/A side was zero. The D/G side is 5.6. Pickup is a Seymour Duncan Quarter Pounder P-Bass p/u.....thanks!
 
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#4
You need to drop the assumption that the wiring is correct - there's a pretty good chance it isn't.

P bass pickups are wired in series, so the fact that the D/G half is working means that neither side is electrically open - there is continuity, or you would not hear anything. The D/G half is normal (you're hearing it), but the E/A side (given no output) has to be shorted, either internally, or something else in the circuit, or some other metal is shorting it. Your meter readings confirm that. As pickups don't fail that often (when they do, they typically fail open), the likely candidate is a wiring error, or something else (shielding, perhaps?) is shorting that coil. "Dropping the height of a pickup" could have lowered it onto a shield plate, or moved a wire enough to touch something it wasn't touching before. Or there's foil on the back of the pickup that moved.

This should be easy to troubleshoot - for someone that's used to such things. The fact that you bought a loaded pickguard, though, means you're not at home with such things. That's OK.

P basses are very simple circuits. I'll give it a 90 percent chance that this is fixable by moving something relative to something else. The trick is to fix it so they don't touch again in the future. Look for something obvious, if you don't find it within a reasonable time, this shouldn't cost too much for a pro to fix - it's a 15 minute fix for an experienced guitar/bass tech.
 
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#5
I copper shielded the entire cavity. There is no shield plate just foam between the PU's and cavity. Assuming that it's too low and needs to come up, what could I put between the copper and the PU to allow me to drop it without touching the cavity other than electrical tape? I have done very little work under hoods and do appreciate the simplicity. I have a tech guy but it makes no sense that this is not working as it is. Thanks.
 
#7
If I read that correctly, you've bench tested the pickups away from the shielding and all of the other metal bits that could be shorting out the EA coil, since I cant see how you'd take measurements with it installed. If there's no obvious signs of damage to that coil, bungled rewiring, or something metal that the magnet has drawn into it, its going to be tough to locate the short. Like the poster before me suggested, post some photos if you can.
 
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#8
BassHole1 said:
I copper shielded the entire cavity. There is no shield plate just foam between the PU's and cavity. Assuming that it's too low and needs to come up, what could I put between the copper and the PU to allow me to drop it without touching the cavity other than electrical tape? I have done very little work under hoods and do appreciate the simplicity. I have a tech guy but it makes no sense that this is not working as it is. Thanks.
Click to expand...
Electrical tape is about the only option to shield the pickup from the copper.
 
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#10
So I took the pickups out and measured them. The neck EA is 5.57 and the bridge DG is 5.63 for a total of 11.2 which I think is right even though they are SD Quarter Pounders and supposedly hotter than regular P pups. The wires on the back of each half pickup were fine, too.

However, I did something here that I've never done before. I put a piece of copper tape on the bottom of each pickup. I don't know why since the cavity is shielded. Anyway, I removed it from each 1/2 and reinstalled and they both work just fine with no hum or buzz. I'm guessing the tape was making contact with both sides of the EA pickup and "shorting" it out....what a bloody Dipstick!!!! I've never done that before on a base or guitar but I saw a picture recently wondered if that would make a difference.

Anyways, thanks everyone......and sorry to have wasted anyone's time.....

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#12
BassHole1 said:
So I took the pickups out and measured them. The neck EA is 5.57 and the bridge DG is 5.63 for a total of 11.2 which I think is right even though they are SD Quarter Pounders and supposedly hotter than regular P pups. The wires on the back of each half pickup were fine, too.

However, I did something here that I've never done before. I put a piece of copper tape on the bottom of each pickup. I don't know why since the cavity is shielded. Anyway, I removed it from each 1/2 and reinstalled and they both work just fine with no hum or buzz. I'm guessing the tape was making contact with both sides of the EA pickup and "shorting" it out....what a bloody Dipstick!!!! I've never done that before on a base or guitar but I saw a picture recently wondered if that would make a difference.

Anyways, thanks everyone......and sorry to have wasted anyone's time.....

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Click to expand...


Oh yeah, anything conductive across those two wires is going to short the pickup leads together. I'm guessing what you saw was someone grounding the polepieces on a pickup. For that, you'd just want a narrow strip of copper tape that only touches the bottom of the polepieces where they stick out of the pickup then solder a wire to that and solder the other end of the wire to ground. However, if the pickup is working normally now there's no need for that, grounding the polepieces separately is generally only for a specific circumstance.
 
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#13
Matt Liebenau said:
Oh yeah, anything conductive across those two wires is going to short the pickup leads together.
Click to expand...
You're right. I had never seen someone ground pole pieces before, Matt, and I'm guessing that is what it was, but I must have let the tape hit the PU leads.
I normally just do the whole cavity and it makes the bass significantly less noisy, and having good PU's and pots/harnesses also helps. I always run a ground wire to the bridge, too.

Now that my "problem" is fixed, I can jam it out tonight.....thanks to all!
 
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