ToneShapers Tech Tips: Avoid Phase Issues When Combining Guitar Pickups From Different Manufacturers 

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Thnaks!

There's no reason you cannot wire Jazz Bass pickups in series, unless you have shorts between the outer polepieces and the inner coil wraps (check for continuity between the outer polepieces and the pickup's black wire with a meter - if no continuity, then no shorts exist). Otherwise, the pickups can be wired in series like any other pickups, but not using the stock Jazz Bass wiring (obviously, since the jazz bass usually doesn't have its pickups wired in series). But there's nothing inherently different between Jazz Bass pickups and Strat or Tele pickups.

Yes, this trick will work regardless of the pickup brand. This method will always tell you if two pickups are in phase or out of phase with each other.

If using the Duncan wires as black to ground and green to hot, wouldn't you get a 'hum' from it if your hand touches the pole pieces ??

Well, that's going to depend on the wiring scheme. The wiring diagram you're working with will specify where the connections go. In the example guitar, the pickup was replacing another pickup, so the hot/ground locations were already known.