This wiring diagram is taken from a 1986 Spectrum GT bass.
It is probably also suitable for the Pantera X750 bass since they have the same pickups (Neck – Magnabass III, bridge – Magnabass IV) and controls (3 way switch, single volume and two tone controls).
- The volume pot is 500K log/audio with a DPDT switch
- The tone pots are 500k log
- The tone capacitors C1 and C2 are 0.047 microfarad Mylar
- Bridge pickup – Magnabass IV, impedance 6.6K per coil
- Center/neck pickup – Magnabass III, impedance 7.4K per coil
Both pickups have 4-core wiring internally, reduced to 1 core for the neck pickup and 2 core for the bridge pickup before being connected to the volume and tone controls, so they can both be rewired simply for series/parallel switching or coil tap. Coil tap is probably only really possible on the bridge pickup without modifying the neck pickup.
The Magnaflux III (Centre/neck) pickup looks like a split-coil pickup in a humbucker case but actually has full length coils each of which only has slugs/pole pieces under a pair of strings, so one coil pickups up the signal from the E and A strings and the other from the D and G strings. It would be a simple matter to take the back plate off the pickup and add 4 more 6mm pole pices per side, then each coil would pick up the signal from all 4 strings.