I'm a Luthier working on a customer's Mid 60's Marvin that needs a bit of assistance! I need one control knob, and a wiring diagram. For some reason, the bridge PUP Tone control is non functional, so if its the Capacitor, I can not make out the original value marking??? Have tried in vain to locate one of these (Chicken Lips) knobs, you know, something one seeks, but never finds, LOL! Hope you can help, or direct me in this "Quest"?