In my experience, with the single coil J in a PJ, you don’t get phase cancellation, you just don’t get any humbucking. Yes, that was the most typical case back in those days, but aftermarket companies like DiMarzio were making humbucking J’s, so it was a typical upgrade.
If you’re getting phase cancellation with any pickup combination, it simply means something is wired wrong.
If you’re getting phase cancellation with any pickup combination, it simply means something is wired wrong.