Any 8-lead humbucker can be wired into a P (or a reverse P, or a J, or an MM...) so long as you know which wire is for which coil and how the polarity is organized. It's a shame I couldn't find any wiring diagrams for Schaller's wiring online; you'll have to investigate some things on your own using a screwdriver, a small magnetic compass a multimeter. I will explain this in detail in case you or anyone else doesn't know how to measure using those three tools, so I apologize if it sounds patronizing. I will also
bold the best-case scenario - if you're in a rush try that first, then if it doesn't work, undo and start debugging.
First of all, since you said there's a set of four green-white-brown-yellow wires, let's assume each set belongs to a row of polepieces (close to the bridge or the neck).
Take a multimeter, set it to 10 or 20 kOhm range, and measure pairs of wires. You should get a result something like this:
- wires one and two (say green and white) have a resistance of several kOhms.
- wires three and four (say brown and yellow) also have a resistance of several kOhms
- wires one and three, one and four, two and three, two and four all measure an open circuit (may be marked as "1 ." or "OPEN" or "INF" or "infinity" or similar)
If this is the case, that means you've identified coil one in the top row as using the green and white wire, and coil two as using the brown and yellow wire. Wire that down. In case another two pairs of wires give you a good reading and the others give you an open circuit, write down the correct pairs. If you tried it and you get other readings, post them here.
Repeat the measurement for the second row of coils and write that down as well.
Now, let's say you got the wires from the example in for both rows: green and white are coil one, brown and yellow are coil two. To get the pickups to act as a P-bass, you need the bass coil from the row that'll face the neck, and the treble coil from the row that'll face the bridge.
So you take the (example) green and white from one row, and the (example) yellow and brown from the other coil, or whichever combination was that gave a solid reading.
To make sure the pickup actually acts as a humbucker, which it should in order to get a full tone and no hum, the two coils you're going to connect need to be electrically and magnetically out of phase.
To check the electric phase, do the following:
- connect the probes to the (example) green and white wires. Connect the hot probe to green, ground probe to white
- set the multimeter to 100 or 200 mV because we'll be measuring very low voltage
- place a heavy screwdriver on top of the coil you hooked up, wait till the multimeter resets to zero, then lift it away from the coil
- mark the polarity (+ or -) of what the voltmeter picked up
- unhook the first coil and connect the second - hot probe to brown, cold probe to yellow
- repeat the screwdriver test and mark the polarity.
If you got two different prefixes (one is +, the other is -), that means you need to connect the ground of one coil (the wire that was connected to the ground probe of the multimeter) to the hot of the other coil, so you can solder those two together. In the above case you'd connect the white to the brown.
If you got two equal prefixes (++ or --), one of the coils needs to be connected reversely. In the above case you'd connect the white to the yellow.
Once you've got down what needs to be soldered where, solder the two wires together, insulate the solder so it's nice and safe, mark your start (green) and end (say, yellow) and tape off all other wires so they don't accidentally touch anything.
Finally, to check the magnetic phase:
- lay the pickup on its long side, then bring a compass to one of its coils from the front (say, the one you picked the green and white coils from).
- The needle should turn and face the polepieces with its N or S side. Note that down
- Bring a compass to the brown and yellow coil
- The needle should turn and face the polepieces with the opposite side
If you get one reading (say N) from one coil and the other (say S) from the other coil, you're good to go. Otherwise, you'll need to check the back of the pickup. If there are flat magnets underneath, you can just flip the one underneath either of the pairs. That'll make sure the two coils are also magnetically out of phase.
After you've done all that, connect your pickup to the switch, volume, tone, output, preamp, what have you. The pickup should sound very close to a P-bass, though it might not have all its fullness as it is a double-J pickup, and the coils are narrower than on a full P-bass - still, it should sound good.
If you need clarification, do one step at a time and post back after you're done and we'll see it from there.
