I recently (today) acquired a Strat that has a 4 position rotary (with detents) pot in tone 1. It only impacts the bridge pup. There are slight differences in tone. All sound strat like, but position 2 on it is like pure strat with no hum. Research has not pulled up anything. Before I pull off the guard to see what's going on, anyone have any thoughts? The papers with it offered no insight.