need help diagnosing pickups/wiring + question about soldering on actual pickups

[chunger]

Hello,

Not being a very electronics-literate person, I have a couple of questions regarding one of the SX basses I modded. The problem is this bass is experiencing low output and the tone is thin. . . otherwise, all aspects of the controls are functioning correctly. The bass is actually functional, but I know from building another bass with identical electronics and pickups that the output should be much hotter and tone thicker than this bass exhibits. Here is a picture of properly functioning harness (identical to the one I'm diagnosing)

Here is the configuration:

Nordstrand NJ4SE split coils humbuckers neck and bridge set up with 4 wires to tap the coils individually. These pickups IME are wound fairly hot and are pretty ballsy.

Wiring configuration (Note: wire colors in the diagram were drawn for DiMarzio Model J's, and the corresponding Nordstrand wire colors are different).

This is wired with 3 push/pull pots for series/parallel switching on each individual pickup and the a global series/parallel switch. As mentioned before, the controls are functioning as expected. All pickups work singled. . . output on each pickup is higher in series mode than in parallel. . . global series mode increases output as well. Tone knob functions as normal. . . just low output in general. Side note: This wiring harness was functioning with normal output when DiMarzio Model J's installed.

I've been over this thing many times tracing each wire to make sure I have adhered to my wiring diagram, and I have not made any obvious, silly mistakes in soldering or wiring.

per communications with Nordstrand, I've checked DC resistance of the pickups and I am not finding any problems there: in series 11-12k ohms dc resistance neck (5-6k per coil at the eyelets) and 13-14k ohms at the bridge. (6.5 to 7k ohms per coil).

I've also checked that there is no shorting of any coil wires with the separate grounding wire for the pole pieces. the only fishy thing I found when prodding around with the multimeter is there is not good grounding between the pole pieces and the bare grounding wire on this pickup (some poles read no continuity to ground wire, some read resistance). . . but that ground should only have an effect on general buzz or noise, not pickup output, right? Unless one of the coil output wires is shorted to the bare ground wire which they are not. While running DiMarzios, the harness had 500K pots on both Vol controls in an attempt to bring a little more treble. I have switched those out to 250K pots again because the previous bass was running great with those and Nordstrand recommended them.

Here is the harness as it sits right now:

I wanted to make sure I had exhausted all diagnostics that are practical to verify that the wiring harness on the bass is functioning properly prior to blaming the pickup and sending back to Nordstrand for repair (don't want them wasting their time on account of a squeaky un-informed client). I also want to perform all practical diagnostics on the pickup itself prior to sending it in.

This may show how little I know about these things, but:

Could the pole directions be switched around effecting output?
How do I test pole directionality North/South?
Could the pickup be wired out of phase somehow that would entail an easy fix? How do I test that?

The only pot in the system that has not been changed out is the tone pot, but it was functioning fine previously with the DiMarzio pickup, and it does indeed seem to be functioning fine now along with the other controls.


I do have another set of new Nordstrand NJ4SE's on hand except it is not set up with the 5 wire harness (4 coils wires + bare pole piece ground). I was wondering if there are any special dangers or methods required to solder and desolder the pickup leads on the pickup itself. The temptation for me is to simply swap pickups, but the new unit would have to be modified with 2 additional wires. What temp should I set my iron to for this? Is there possibility of damaging the coil wires? Or compromising the wax potting?

If it's a pretty straight forward operation (same as soldering anything else) I'm tempted to try. Otherwise, I'd hate to de-value the pickups for someone else in the future.

Any suggestions or recommendations for repair or for further diagnosing would be much appreciated. This configuration is such a PITA to wire up .. . hopefully once this is sorted out, nobody will have to touch it again for a couple of decades.

Side Note: I am aware that many folks on forum who actually know something about electronics assert that star grounding has no effect on buzz or hum, but I continue to do so out of habit despite the advise. I assume it can't hurt anything either when done correctly.

 

[chunger]

went a little stir crazy tonight and decided to try and resolve my issue. So, I looked at the wiring on the NJ4SE pickups stock and custom with 4 wires. . . and decided to swap pickups and see if the problem goes away.

Stock NJ4SE

Custom 4 wire NJ4SE

I figured I could add 2 wires to the stock one without much issue. The only wire I had on hand is 22 gauge silver plated teflon wire, so that's what I used. . . apparently the Nordstrand wire is 24 gauge. Hopefully this won't be too much of an issue, and hopefully it'll fit in the little hole between the pickup cavity and control cavity. The 2 options were to chop the little jumper wire inside the pickup and splice in my wires (not much space inside). . . or, de-solder the jumper wire from the pickup and solder in my own. I decided to de-solder for a cleaner install.

First thing was to pull the pickup leads back up and enlarge this hole to fit 2 more wires:

Then, I put a paper spacer in to guard he coils from solder splatter and heated up the solder lug and removed the jumper wire (pickup is voiced to run in series and is wired as such from Nordstrand stock). Then, I heated the lug again and inserted my new wire. . . after the new wire was placed, I heated again and added solder to mechanically secure the joint into the pickup body. . . nerve-wracking for me because I know these pups are expensive and I'd never done this before.

The 2nd one went smoother, and after soldering, DC resistance measured normal on all coils. . . what a relief.

I made note of my new color changes. . . the inside black markings are the colors as supplied by Nordstrand (4 wire), and the outer blue markings are my current colors.

And. . . luckily everything fit, and I installed the pickup. . . this exact pickup was used on this bass previously prior to doing the 4 wire series/parallel switches to test the NJ4SE's in studio, so I know the pups work (if I didn't destroy them just now with my hacking).

What a mess.

All buttoned up, the bass seems to be outputting a hair lower than my other prototype pickups, but in the same league and certainly not thin sounding anymore. I'll have to verify if this was indeed a success on Thursday because i have a recording studio session planned to gather more audio data on the new set of builds, but it is looking promising right now, and I guess I've figured out a way to turn a standard NJ4SE into a 4 wire version.

 

[Stompin Tom]

Were the original pickups thin sounding when played individually, or just when played together?

 

[joeyl]

here is my take on it:

I used NJ4SV not the SE, and I had problems with the tone being thin, especially on the A string. I changed strings but it was not the string itself. I played with the height of the pickups and that did not fix it, I could still hear the drop in output when the pickups were in parallel or series to each other. I then swapped the pickups with SGD J pickups which use twin parallel blades for humbucking instead of the split coils, and the problem went away. I talked to David, SGDs maker, and he said that it is possible that some pickups with the split coil design would experience weird cancellation like that.