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85/15 TCI Dissection, troubleshooting, wiring help


New Member
Apr 8, 2022
Long post alert! Please bear with me

Hi everyone,

First post here, but I’ve perused this forum endlessly before joining. Excellent insight to be had. Good company.

I am a PRS pickup hoarder, and scored a set of 85/15 TCIs last month. I was working on installing them in one of my Les Paul’s. They are the multi-tap variant with the green wire, and I understand these are NOT your typically wired humbuckers. I did my research though and I am fairly confident it was wired correctly.

Context: for low strength alnico magnet-pickups that I buy and don’t know the history of, or if I think they were exposed to stronger magnets at some point, I hit them with a set of neodymium’s to charge them before install. I did so with these, as I believe the 85/15’s use AL2 (I believe all of the 5X/XX pickups do, actually). Could be wrong but I don’t think I am.

Well I installed them with a wiring similar to the older 408 style wiring setup: two DPDT switches (push pull mounted, irrelevant Except that they are On/On) with red white on the top pins (orientation swapped between neck and bridge for phase), ground and hot on the middle pins, and green black on the bottom pins.

Sorry I can’t post any links or images yet.

But this should wire it so that when in the down position, a full humbucker with balanced coils is selected, starting at the screw “start” and ending at the slug tap, omitting the extra slug coils.

When up, this *should* have the slug coil only, coil tap to slug finish, using the extra coils.

The wiring diagram for the guitar these came out of (a 2020 CU24, not Anniversary or -08) shows the bridge leads configured this way but going to a DPDT push/pull, while the neck wires go straight to the 5 way switch.

Of course, with this being a Les Paul, I’m using a 3 way switch with independent volume and tone: so the hot lead off the DPDT goes to the first prong on the volume pot, standard LP wiring from there. Correct me if I’m wrong, but this should still work.

I’ve tried wiring it twice to make sure I wasn’t having any issues with cold joints or anything, but the signal and tone is really weak and anemic. The split activates, I can tell, and the neck pickup sounds “better,” but still not full. The bridge sounds awful. Quite consistent with a magnetization issue, maybe a phase issue, but I don’t think so.

SO I finally digress…given that I’m fairly certain I’ve ascertained the wiring points for the MTs, and that they’re wired in an appropriate manner, I’m suspecting the neodymium “recharge” as having demagnetized, or magnetized differently, even though I ensured Correct polarity orientation before doing so. Keep reading though, cuz the magnets get weirder (yes that’s an S on the end).

Also wondered if I had somehow damaged the wires, even though both pickups measure out good and at the same values as before I installed them.

(Although FWIW, I get an open reading when I read red/white and black/green UNLESS I connect the other two leads, as you’d expect from a standard humbuckers with two starts and two finishes.)

I dissected the pickup. I know, blaspheming, but Paul destroyed a PAF he claimed was the best he’d ever heard to have it’s components analyzed, so SCIENCE.

I’d share pics but I’m unable to yet. I’ll edit this post to add them once I’m deemed worthy by the forum-algorithm-gods.

Interesting points:

1. No maple spacer on the 85/15 which makes sense. There is one in the 58/15 set I have that I can see between the cover and baseplate. The #7 set and #10 set I have also appears to have them. Guessing all “vintage style” PRS hums have them.

2. Magnet is smooth, no rough cast. Red marks seem to indicate north on the main magnet.

3. The main bar magnet has a “slice” down one side, asymmetrically. Almost seems like one side, screws or slugs, is intended to have a stronger field applied.

Next, The most pertinent point: this isn’t unheard of in pickup-making, but I’ve never seen or found it discussed with PRS pickups, though I know Paul keeps it secretive as much as possible.

4. The 85/15 uses 3 magnets. I don’t know if this is part of the TCI process, but there is one main magnet as you’d normally find centered in a hum. There are 2 skinnies, one on each side of the magnet, but they aren’t polarized side-to-side, bobbin-to-bobbin. Rather, THE SKINNIES ARE POLARIZED TOP TO BOTTOM, north to south along the bobbin length.

Now finally the question: is this…a thing? I took a couple college level physics courses including some electromagnetism, and I know a field circles back into itself, so to speak, from each pole. Are the skinnies supposed to be polarized differently from the main bar magnet? Does this counteract or supplement the main field it generates? Does this “tune” the inductance of the coil to create the TCI process?

Looking for help to salvage this pickup set. They’re good pickups and I want to use them; and at worst I could buy another, not touch it with the magnet, and check the internals out, but that’s more $$$ I don’t have.

Any winders or physicists have any experience with pickups/magnets with perpendicular fields? Do I need to individually magnetize each to a different polarization pattern?

Thanks, and sorry for the lengthy post!