yeah, sounds like you have an "A" (audio) on the P pickup and a "B" (linear) on the Jazz; a "B" pot for the P pickup will be more even sweeping from off to full.
also, if this is the classic V/V/T jazz bass wiring, the tone pot can't be set "anywhere", it matters very much here; anywhere but full-up it makes the volumes drop off even faster between say "8" and "10".
as for the volume drop when the J is full-up, if it sounds "good" with both pickups (kinda mid-scooped, with a little more treble on top), then things are normal, you naturally get a little loss from two pickups in parallel vs one by itself.
if it sounds thinner and twangier with the J full-up then that pickup is out of polarity with the P pickup and needs to be reversed.
Guitar Repair Gnome
Alpha Music, VA Beach
Last edited by walterw : 02-22-2013 at 08:37 PM.