Pickup rewinding specialist J.M. Rolph has noted, "How many times have you wired a pickup and found it's magnetically out of phase, with the same thin, low-powered sound as a pickup that's wired out of phase, even though the lead wires looked right?" By indicating the north or south magnetic orientation of a pickup's polepieces, this polarity tester can help you avoid the problem.
Refined by Les Schatten especially for guitar shops, the tester is economical and easy to use. Coupled with a basic knowledge of vintage pickup magnet polarities (instructions are included), it can also be a quick way to determine a pickup's authenticity.