Help troubleshooting P/J bass pickups and controls wiring issue

Fenachrone

New member
Messages
4
This short-scale P/J bass build, which otherwise turned out epic, has got some troubles making the right sounds. I could use
some pickup/wiring help from the experts out there.

The "P" pickup is a Tonerider Precision Plus: DCR 10.6 Alnico 5
The "J" is a Fralin Jazz Bass: DCR 9k Alnico 5

I used this wiring harness from these folks: https://1469music.com/products/xn-fender-pj-bass-precision-bass-wiring-harness-70b

The cavity is painted with black shielding paint and all metal is grounded to it.

Here's what's happening:

So... All pots at full, there's sound. Turning down P volume pot, in only a short distance of its travel, the sound shifts suddenly in tone in sort of a phase-y way. It's not a linear process at all.

Again, all pots turned up, and then turning down just the J pot a small amount, results in a sudden increase in volume.

With the P volume off, though, the J volume has a linear feel and seems to produce normal tones.

Inversely, when the J volume is off, the P volume seems to work normally. But then, once you turn the J volume up, it has no effect until the nearly the end of its travel, where the overall volume drops off sharply.

Moving the tone control doesn't seem to do much but there is some subtle tone alteration.

I'm not a pro at wiring but know enough about soldering to be reasonably good at it. I followed the wiring diagram closely.

Thoughts?

Pickup incompatibility? Flaw in the harness? Some solder wind up somewhere it shouldn't have?

All responses appreciated...
 

Spud

Senior member
Messages
915
Could it be a result of the pickups being out of phase with each other? Guessing. Or is there an inadvertent bit of solder or wire touching something adjacent to where it is soldered? again guessing.
 

Fenachrone

New member
Messages
4
Could it be a result of the pickups being out of phase with each other? Guessing. Or is there an inadvertent bit of solder or wire touching something adjacent to where it is soldered? again guessing.
Well, those are good guesses. I thought about the phase issue, but wouldn't have believed that could happen with pickups. Isn't their design inherently straightforward? Maybe someone can comment on that. Without any other possible cause of the problem, I'm going to take the harness out and inspect for any bad solder issues.
 

TBurst Std

Senior member
Messages
2,589
Pickups are not inherently in phase with each other. So toss out that presumption.

Have you reached out to the mfgs to see what phase the other pup is expecting? Also why grab a diagram from someone who didn’t even build your pickups?
 

DuckBaloo

Senior member
Messages
276
Isn't their design inherently straightforward?

No. Especially for single coils like the Jazz bass PU.

A coil can be wound clockwise or counter-clockwise; their magnets could be north pole up or south pole up. Every maker has their own preference, missing PU brands requires a lot of homework.

If one of these (wind direct or magnet polarity) is flipped between two single coil pickups, it’s out of phase, if both are flipped, it’s RWRP, in-phase but hum-cancelling.

Even Fender is unpredictable, around ‘57 or ‘58, Leo changed “stock” polarity, so Fender PUs are all over the place on phase depending on whether they are modern, RWRP, early-era RI or late-era RI.

All this said, it sounds amlit more like your pots are miswired, since the change happens when you turn down. Or, it could be both?
 

Fenachrone

New member
Messages
4
A phase issue turned out to be the problem. A rep from Fralin pickups, the maker of the "J" I used, confirmed my suspicions and those who commented here. Once corrected that, all was normal.

Thanks to all who offered causes and solutions.
 

Spud

Senior member
Messages
915
A phase issue turned out to be the problem. A rep from Fralin pickups, the maker of the "J" I used, confirmed my suspicions and those who commented here. Once corrected that, all was normal.

Thanks to all who offered causes and solutions.
Glad you got it fixed up!
 
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