My Maxon OD-820 tubescreamer just stopped working for some unknown reason. When hooked up and turned off, the signal goes through the pedal fine, but when I turn it on, the signal is almost completely cut out and I can just barely hear it coming through my amp with no gain or volume. I thought at first that the battery died, but I changed batteries and it's still doing it. Anybody know why it'd be doing this? I don't know what's wrong with it...