Got a problem that happened tonight With my MTD Kingston z 6 want to see if any of you can diagnosis it. When i plug it into my amp its not making any noise (i know its not the amp because my other bass works fine) When i turn the MIDDLE KNOB ON THE BOTTOM ROW it makes a popping noise. This knob is a push pull and it makes the popping noise when turned.. pushed in or pulled out. I checked the battery with the good old tongue method and it seemed to be fine but i replaced it with a brand new copper top anyways. Any ideas???