I have (I think) an old JB in my Charvel, and two single coils that i'm not sure which model (they have hex pole pieces). My problem is that when i switch to the JB only, the sound is very empty, light, and trebley. It used to just wail. Switching to either of the single coils brings the oomph back, and the tone knob works just fine with them. I plan on pulling it apart on the weekend, so should I consider this a potential wiring issue (since i'm pretty sure the pots are fine), or has my trusty old JB crapped out on me after all these years? Any help would be great.