FOREWORD – I had posted this morning the message below and have redone it for two reasons:
-The color code was NOT suited to Duncan pickups. Corrected.
-The wiring that I explain uses the green wire as a ground for the bridge pickup BUT as the HOT wire for the neck one. It will only work if one of the magnets of the set has been reversed, or the sound will be OOP. This mod should also buck the hum when both North coils are in series…
I've added a mini ON/ON switch to the schematic and will try to explain what is going on. grey color on the schematic = white wires of pickups. I've renamed the two sides of the switch "X" and "Y" to make things clearer. Not sure it worked.
IF I've done another error somewhere, THX by advance to correct it. My head is spinning too, more than ever... ;-)
Mini switch on the LEFT : original diagram with the positions explained above as in the original pic… I've patiently checked the idea, it seems to work.
Mini switch on the RIGHT (new options):
Black of the bridge PU is now permanently connected to volume. Its Green wire is permanently connected to ground.
Position 5: nothing changes.
B pickup enabled, coils in series.
Position 4: red and white wires of the bridge PU go altogether to the neck pickup, whose all wires are themselves going to ground and therefore, shorted .
Black of the B pickup still goes to the volume so only its North coil is enabled. Nothing new, IOW.
Position 3: black of the N to ground. Its green, white and red wires are altogether connected to the common side of Y, closing the South coil of N on itself. This common goes to the red and white wires of the B pickup. It opens to a new configuration:
North coil of the neck PU is in parallel with South coil of bridge PU, from the ground. They join to be in series with the North coil of the bridge pickup, itself connected to the volume. It’s a 3 coils configuration, half parallel, half series.
Position 2: North coil of the N pickup enabled... its black goes to ground, its W/G/R go altogether to common lug of side Y, going itself to common of side X, going itself to R and W of the bridge pickup, going themselves to the volume with the black of the B pickup. North coil of B pickup shorted, consequently. But the green wire of the bridge still goes to ground and its red to volume. Result:
North coil of N and South coil of B in PARALLEL.
Position 1: neck pickup enabled, both coils in series. Same thing for the bridge pickup. IOW:
both HUMBUCKERS should be now in PARALLEL.
Where have I done a (new) mistake? LOL...
FWIW. It was a mind boggling but funny intellectual challenge. Maybe it will be useful too, unless I've lost my mind in the process. Time will tell... ;-)