PBG Humbucker 4-wire mod and magnet upgrade

4-wire pickup mod

I wanted to add a coil split option to the SG-1F I'm building for my nephew, and rather than buy new pickups just for the coil split I decided to modify the pickups that came with the kit. The aim being to convert the stock 2-conductor, mystery magnet, PBG humbuckers into 4-conductor (plus shield), Alnico magnet powered, tone monsters. A 4 wire pickup with separate shield allows you to access each coil individually, which permits series/parallel switching, selectable single coils, phase changes etc. It doesn't mean you have to do any of that, but the option is there if you want it.

DB has previously posted a great tutorial on coil-splitting a PBG humbucker, so if all you want is to coil split your pickups then his method is the easier option. It is less involved and has a lower risk of destroying your pickup. If you want to learn how to determine a coil's polarity and magnetic pole orientation etc, then this video is a useful place to start.

This walk-through is simply the method I used to convert the pickups to 4-conductor and upgrade their magnets. There may better alternatives/techniques, so consider this just one possible way of doing it.

Warning: Do not try this unless you are willing to potentially ruin a perfectly good set of pickups!

A quick check of the stock pickups with a multimeter showed the bridge as 11.12K and the neck 10.68K. Using a magnetic compass showed that the screw coil of the bridge pickup is a south magnet, with the slug coil being north (north on the compass points to a south magnetic pole). Same process for the neck pickup showed its slug coil as the south pole and the screw coil as the north. This is important for replacing the magnets, and if you want to run split coils across pickups as hum-cancelling pairs.

First step, remove the pickup rings.
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Next is a slightly tricky part, removing the chrome covers. These are soldered at two points to the base plate, and you have three choices: break the solder and risk kinking the cover, saw/cut the join which can get metal filings in the pickup, or de-solder/melt the solder enough to lever the cover away. The latter option is difficult as you need a very powerful, ideally temperature controlled, soldering iron, as you need to quickly heat up the solder point, separate the join and then remove the heat before it starts heating up the whole pickup. If your iron isn't powerful enough you'll have to sit it on the join for ages, which will heat soak the entire pickup and start melting the wax and possibly other bits… this would be bad. I used a combined method of quickly heating the solder while gently prying the cover's side away from the baseplate. Leave the mound of solder on each side as you'll need it re-attach the cover.
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Once the covers are off the bobbins are exposed and you have access to the stock wiring connections… I'm going to cheat and use these to attach the new 4 conductor wires, as trying to connect directly to the ultra-fine copper coil windings is just inviting disaster. The coil windings are unbelievably fine and often quite brittle so, inevitably, you will break some of the wires while trying to connect to them, and if you break a coil start wire… it's game-over (you can't unwind more to reconnect it). As an example, here's the bobbin of another pickup showing the copper coil winding wire start (left) and end (right)… incredibly fine and too easy to break.
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So, I'm taking the easier and safer route and using the connections that are already there, as explained below:
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Bridge: 2-conductor wire (yellow) still in-place.
1. Shield/bare wire connection to Bridge South Start (the shield wire is connected to both south start and the baseplate at point 5).
2. Black link wire connection to Bridge South End (the black wire links the end points of each coil).
3. White (hot) connection to Bridge North Start.
4. Black link wire connection to Bridge North End (the black wire links the end points of each coil).
5. Shield wire connection to Bridge baseplate (provides the shielding link to the baseplate and chrome covers for hum reduction).

Neck: 2-conductor wire (red) has been cut at the end of the outer covering, and the black link wire cut at its mid-point. The wires must be carefully cut so that you have enough wire available to solder connections to later.
6. Shield/bare wire connection to Neck South Start (the shield wire is connected to both south start and the baseplate at point 8).
7. Black link wire connection to Neck South End (the black wire links the end points of each coil).
8. Shield wire connection to Neck baseplate (provides the electrical shielding link to the baseplate and chrome covers for hum reduction).
9. White (hot) connection to Neck North Start.
10. Black link wire connection to Neck North End (the black wire links the end points of each coil).

Clear as mud? Basically, the south start becomes your ground, the north start becomes your hot, and the south and north coil ends are linked to produce the hum-cancelling effect.

Once you have access to the (short) cut wires connected to each coil's start and end, you need to very carefully strip the ends of the covered wires. It's probably best to use a sharp knife for this as you can't afford to pull on these wires at all, as you may detach them from the coil winding or worse break one of the fine coil wires. Also, de-solder and remove the clipped shield wire from the baseplate (it may be easier to do this once the baseplate is removed in the next step)…
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Replacing the magnets on these pickups is complicated somewhat by the fact the manufacturer seems to use glue as well as wax potting, so there's a messy mix of wax and gummy glue holding the magnets in place. So, to get them out it's easiest to remove the baseplate from the coils via the four phillips-head screws on the underside.
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Then, it's a matter of carefully prying, levering, and separating the glue to get the magnet out (you can see the stringy, gummy glue residue below).
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If all you want to do is replace the magnets, you may be able to just loosen the four screws and then carefully tap out the old magnet with a screwdriver (glue permitting) without removing the baseplate.
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Once you have the old magnets out it's time for the shiny new ones to go in. In this case I'm using an Alnico 2 for the bridge pickup and Alnico 5 for the neck. Again, you need to use a magnetic compass to work out which pole is which (compass north points to a south magnetic pole) and ensure the new magnet goes in matching the orientation of the old one. As I determined at the start, the bridge screw coil is a south pole and the neck screw coil is a north pole.
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Poles checked and re-checked, and shiny new Alnico magnet set in position.
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Out of interest, I weighed the old magnets and the new Alnico's. The old ones were 11g, and the new Alnico's 19g… quite a difference. And, in case you didn't know, Alnico is quite literally the alloy used in the magnets: Aluminium, Nickel, Cobalt (AlNiCo).

Time for the big moment...

Work out how long you want you pickup leads to be, neck is usually longer, and then strip the covering and tips of the individual wires. Feed the new lead through the baseplate and then solder the bare shield wire to the baseplate at the same point as the old one. Helping hands/clips and small vice etc really helps at this point, as you need to keep the lead steady on the baseplate and positioned very close to the coils (I found it best not to re-attach the coils to the baseplate just yet). However, if the glue holding the two coils/bobbins together has become separated then it would be best to re-attach the coils to the baseplate once you've soldered on the shield wire before proceeding further (see paragraph below on how to re-attach the baseplate). Once you have a stable set-up… very, very, very carefully solder your 4 conductors to the coil wire stubs. And, I do mean carefully, as any pulling on the coil connections could detach/break the wires.

I decided to use the standard Seymour Duncan colour-coding: Green = South Start (ground), Red = South End, White = North End, Black = North Start (hot).
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Note: I put heatshrink on the base of the bare wire (south start) before soldering the connection to it (green wire), just to help ensure it couldn't short out with anything once the pickup is sealed up again.

At this point it's a good idea to use a multimeter to test your connections, make sure your lead's coil pairs (green and red, white and black) work, and that nothing is shorted. Once you're satisfied, cap the connections with some heatshrink tubing so there is no possibility of shorts.
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I carefully re-attached the coils to the baseplate using the four screws, making sure the magnets were evenly positioned and that the pickup lead was sitting in the right spot. Be careful tightening the four screws as over-tightening them will tend to flare the coils apart and outwards. I then tucked the new connections between and around each side of the coils and used a couple of tight winds of fabric pickup tape to secure everything. Ready for the cover to go back on!
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Re-attaching the covers is similar to removing them, but harder. You have to get the solder points hot enough for the solder to flow and make a solid join (more difficult than breaking to joints) and again remove the heat before everything else melts. I ended up using two soldering irons, one on the cover's side edge and the other on the baseplate, to get the joint attached as quickly and solidly as I could.

Covers re-attached, rings on, 4-conductor Humbuckers with Alnico magnets.
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Once they were finished I did some quick tests… with interesting results. The change of magnet has produced a slight change in resistance, making them marginally hotter, which means the original magnets were a touch weaker than I expected. I guess the extra set of joins to connect the 4 conductors could also maybe nudge the values a little.

Bridge:
Original value (old magnet) = 11.12K
New value (Alnico 2 magnet) = 11.57K

Neck:
Original value (old magnet) = 10.68K
New value (Alnico 5 magnet) = 11.24K

I also did a quick back to back test using my one string test board, comparing the 'new' humbuckers with another stock set of pups. From what I can tell, the 'new' sounded thicker but with more clarity and better defined highs. But, I'm just guessing until they're actually plugged into an axe. I also tested the pickups split, which gave a nice single coil sound, and then tried linking the Bridge south (green and red) with Neck north (white and black), and got the expected hum-cancelling which is a good sign.

I haven't re-potted the pickups, as pretty much all of the original wax is still in place, but I won't really know if it's enough until they're played at volume. Also, I've noticed on a couple of sets of these stock humbuckers that the screws on the screw coils don't always actually screw for adjustment… it seems more like just wax and the magnets are holding them in position. I may need to take some remedial action on this eventually, just see how it goes.

For now, I'm really pleased with the result: a set of PBG 4 conductor Alnico powered humbuckers ready for my nephew's SG.