
Originally Posted by
Funkfingers
Need to see photographs of your actual wiring before hazarding any comment.
With traditional VVT Jazz Bass controls, it is normal for there to be a "notch" sound whenever one pickup is set for full output and the other is partially rolled off. This is a direct consequence if how the two pickups are adjusted relative to the strings. It is usually judged by ear.
With a balance control in circuit, there is no guarantee that the centre detented position on the pot provides exactly fifty fifty volume mixing. Your pickup adjustments could mean that the balance control centre position sits in one of the two "notch" positions where the sound would be expected to be honky.
Of course, it is possible that one of your pickups is faulty. More likely is untidy soldering of the pickups to the balance pot.