I am trying to fix this used violin bass and it currently makes no noise at all. It has some very ugly solder connections and unfortunately the wiring does not completely match any Hofner diagram I could find. One of the yellow wires on the second volume knob (right) were connected to the bridge pickup and the other wasn't connected to anything. Then the ground on the bottom of the first volume pot (left) was connected to the ground and the neck pickup. All the parts read correctly with a multimeter but still does not make any sound, could anybody give me a hint as to what might be wrong or direct me to a diagram?