I have a seventeen year old Sting Precision (in my avatar) which I play a lot--almost always with the chrome pickup and bridge covers (period correct) installed. Strictly for the look, and as a thumb rest. Sound guys have always loved it. A month ago, I removed the neck pickup cover and--right away--sound guy says he's getting a 60 cycle hum. Not my problem, right? Dodgy house wiring, blah-blah, blame the bass player right? Anyway, I put the pickup cover back on for no particular reason, and the hum disappears (same venue)...is it possible there was a reason for these things in the first place? Keep in mind, I am not an expert on any of this, but it seemed oddly coincidental.