I have a Warwick corvette with an EMG J-set and a Bartolini NTBT onboard preamp. I last used the bass on Tuesday, and when I plugged in today I was getting no output. I had the pickup select knob set to both on, but when I moved the knob forward (clockwise), which up until now I was sure was the neck pickup, I got no response. When I roll it even a little past the midpoint (going counterclockwise), where you feel it bump, the bass comes back on with the neck pickup only. There is a very weak signal (I'm talking barely perceptible) when the knob is set to the midpoint or more forward. Any suggestions? I already sprayed the pickups and control cavity with canned air.