Okay, this one is a little more complex than the regular wiring dilemma. I am no stranger to wiring, I've modded all my guitars and never had a problem I couldn't solve. This is a bit different... it's also the first time I've mixed pickups from different manufacturers.
Guitar is a PRS Baritone with a PRS HFS in the neck (yes, treble pickup in the neck) and a BKP Ceramic Warpig in the bridge. According to this
http://www.docstoc.com/docs/26737432/PAUL-REED-SMITH-PICKUPS-WIRING-DIAGRAM and a few other sources, the HFS has the magnet polarity reversed. The screw coils are north, and the slugs are south.
Now I wanted to do a coil split on these pickups, and I wanted hum-cancellation in the coil split position when both pickups are active. So I deliberately arranged the pickups NS NS (both "screw" coils on the outside). I put screw in quotes as my Warpig has bolts so there is no visible difference on the two sides. Now, using a push-pull, I move the hot coil on the HFS from black to red so I can get the slug side tapped, and move the ground on the warpig from black to white+green. Because of the reversed magnets now when tapped I have the south coil of the HFS and the north coil of the warpig in parallel, both getting ground from the right and taking hot from the left for a hum-cancelling coil tap. This is in theory how the PRS pickups themselves work to get the 5-way inner-outer coils.
So I wired this up (as attached) and test, coil tap works, both pickups work alone. However, in parallel, I get a huge volume drop, scratchy sounds.. uh oh. Out of phase. Double check all the wiring. Done correctly. Test pickup polarity using another magnet. It is indeed NS NS starting from the neck on the left and going to the bridge on the right. Check which coil is tapped by tapping the slugs and screws with a screwdriver. Indeed, got the slug side tapped on both pickups.
So I reverse the red and black wires from the Warpig, to put it in theory "out of phase". Now it is in fact, in phase, and everything works. Hook up a voltmeter to ground and hot and test pickups independently. Both cause negative voltage in the 2VDC range when a metal object is brought close to the pickup. So they are both indeed now in phase, despite being wired out of phase. Check the coil tap, and now the screw side closest to the bridge is tapped. This kind of sucks, the coil tap on the Warpig is actually lower volume than the HFS due to being too close to the bridge now.
So I can fix this, by fixing the ground to the red wire on the Warpig, and instead moving the hot from white+green (coil tap) to black (full humbucker).
But what is going on here? I've verified the magnets on the pickups are indeed the polarity they should be. I've verified the output of each pickup independently, and together with a multimeter, and most importantly my ears. Definitely reversing the polarity of the Warpig fixes the phase problem, but it shouldn't... Have I done something bone-headed in the wiring? I don't think so, certainly can't spot it. I've verified all grounds, everything works, I've triple checked all connections are done properly, even clipped in and independently verified the wiring to all four coils.
Is it possible that one of these pickups is actually reverse wind? I didn't order them that way, and I've never heard of PRS pickups being reverse wound, but since it is an option with BKP I wonder what are the chances I might have accidentally gotten an RW pickup?
If so, can I just flip the magnet in the Warpig and then install the pickup backwards (so I still get a north coil on the inside to help hum-cancel in parallel coil tap mode), or will this not fix the winding problem?
