I had installed a "tab check" similar to the one in the Troy detector, so smarty pants me wanted to really sport my stuff and reset the g/b via power ground balancing as per Monte and Tabdog. Well, I reset the buggar and all of a sudden I got nothin' coming out of the speaker! After looking, I'd broken a wire going to the on/off pot and went back home to solder it. When I turned it on-NOTHING. I could feel a tightening you know where. Finally noticed that I had accidentally put in a battery off the shelf that I had thrown away-but not put in the trash yet. When it powered up, I told my wife that I wouldn't open that thing up again.