Well, I had the same problem, the amp worked and sounded great for 2hours and once I switched to the without horn input it shorted the fuse, then every fuse after that no matter which input I was connected to. I believe once it shorts it becomes an internal amp problem that cant be fixed. In my situation the amp had to go back to ampeg, but while I was waiting for the new b200r to come in I went with a new Nemesis RC115 combo instead. I still dont think the music shop has the new b200r replacement in yet and its been about a month! Just for kicks I was going to go by there when, if ever they do get it in, to see if it has the same problem. 
