Most guitar players don't get the most sounds out of what most humbuckers have to offer. Jimmy Page got around to it in the 80's. Story is he had some engineer design a switching system for his Les Paul using four push pull pots that incorporated coil splitting, phase reversal, and one pickup running in series into the other.
I recently had a customer come in with his Les Paul for a pickup swap because his current tone wasn't squeezing anyone's lemon. He also asked for phase switching and coil tapping without naming he who has two necks. Since I only rely on the internet in matters of love I didn't scramble for existing wiring diagrams, instead opting for a pen, notepad, and an amount of free time only an underemployed guitar tech has in the middle of the day.
I pride myself on my switch skilz. Jimmy can afford to pay an engineer to draw out this complicated scheme. I imagine a degree in such things will get you the result much quicker than I did. Point is I did it without a single class in electrons. And here I offer you a class in electrons. Or guitar switches. Yea, forget electrons, you don't need to know about those to understand basic guitar electronics.
This is the mess we're dealing with. Each push pull pot is a DPDT switch. Double pole double throw means that there are two independent sections that can be in two states. There are four switches total, each with two columns of three tabs. The teal lines represent the switch wiring tabs. The center row is known as the common. The common tabs will be connected to either the top or bottom rows depending on the switch position. The green lines are the potentiometer tabs. These control the volume or tone or whatever else you wire them to do. I don't know about those other symbols, I just think they look cool.
So how do you wire all this to two humbuckers with four leads each (five including ground wires) to coil tap and reverse phase keeping in mind the goal that each switch state should give a unique sound? First draw the above as your starting point, connect the wires where you think they should go, then draw a subsequent diagram for each switch state and follow the electrical path all the way through to ensure proper functionality. Basically it's just trial and error. LOTS of error. So best do it on paper.
Took several iterations but it's better than burning up the switches trying to get it right. To explain the end result I'll first explain our goal. It was not to copy the Jimmy Page wiring. While each humbucker does coil tap and the bridge reverses phase in relation to the neck, the neck reverses phase of one of its own coils while running them in parallel. Page opted to run one humbucker in series to the other. My tweak with the neck coil phase reverse gives you a very pinched, low output sound but with a bit of a boost can yield a great funk tone. Sonically as far as you can get from the wooly, slightly muffled tone the humbuckers in series with each other will give you. Here is the final drawing.
The green and black leads had to be reversed on the neck circuit to get everything in phase with all the switches in the down position but the drawing gets us where we want to be. Let's start with the bridge. Reversing phase is easy, this is done on the bottom left switch. The left common tab gets the black lead. This allows us to change its path to ground or hot. Hot goes to the pots input, ground is ground. You see the "X" pattern connecting the hot of the 1st tab going to the 4th tab and the grounded 3rd tab going to the 2nd tab. Connecting them in this way allows the poles of the switch to be on opposite sides of the circuit no matter the switch state. That is, when the commons are connected to the bottom row, with tab 2 being ground and tab 4 being hot, the left common is going to ground and the right common is going to hot. When the switch is in the second position with tab 1 being hot and tab 3 being ground this sends the left common to hot and right common to ground. It's important to make clear again that the common tabs in the middle are connected to either the upper or lower tabs depending on the switch state.
This alone does not achieve phase reversal as the other pickup leads are connected to the second switch. By connecting the 2nd common of switch 1 to the 1st common of switch 2 we allow for the 2nd common of switch 2 to change states in sync with switch one. This means that regardless of the state of switch 2, the phase will still be determined by switch one. When in the down position (state 1) switch 2 common 2 is connecting the green lead on tab 2 to hot. The "R/W" is the red and white wires together connected to tab 1 of switch 2. When in the down position they are not connected to anything but themselves allowing current to flow from the green/red coil to the white/black coil.
Ignore the bad ms paint job. Use this approach to figure out how each switch state will allow current to flow. I'd make a diagram for each path but that would take as long as wiring the thing in the first place and I've spent enough time on this article already. Switch one reverses the whole pickups phase relation to the neck, which means you won't hear a difference unless the 3 way pickup switch is in the middle position. Switch two is the coil tap for the bridge. Neck switch one reverses phase of one coil only. The second neck switch taps that coil.
I suppose I should throw some subtle errors in there so when you try this yourself using just my diagram you'll screw it up and have to bring it to me but I'm too busy to fix your mistakes. (Nothing worse that trying to salvage burned up switches). Here's the final product. Lots of tiny connections in a tight space. Basically I've just taken a thousand plus words to explain you don't need an engineer to plot out complicated guitar circuits, just a tech with a functional understanding of basic switch operation.
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