I recently picked up a cool beaten up old school guitar cab for a price that I couldn't turn down. I hooked up my D-180 and noticed right away after it powered up that the speakers were just bouncing around in there with some kind of slow random big excursions. Not really producing any volume. I also noticed that the tube power section of my amp was "flickering." I unplugged right away. It's not the amp or speaker cable- I had to rush off to a rehearsal and it worked fine. I've taken the cab apart. All the wires are connected. I noticed an old screw stuck to one of the magnets. Aside from that, visual inspection yields nothing else out of the ordinary. I'd fool around with it more but all of my amps are awesome and I don't want to risk 'em at all. Anyone have any thoughts on this?!