Yeah I wacked my Koch on the door frame on my way to rehearsals last night. No sound for a bit or very low volume. It did work but with the pre-amp volume and master all the way up but somethings not right. It didn't half take a whack though, I heard all the valves rattle. So could it be the a case of take it apart and check the valves? I hope the transformers are ok, they're hand made! I suppose new valves could be on the cards anyway as it's been five years now.
Anyway blinding rehearsal, we were all grining ear to ear! What a buzz :D