So tonight at rehearsal when i turned on my 800RB it made a weak little growl and then stopped working altogether. I tried/troubleshooted everything, it's definitely the head. After changing out most of the cables i tried to plug in again and i got a low hum from my speakers. The cables/cabs worked absolutely fine through the studio owner's own Sunn head. The power light is coming on, however there is zero sound. Is this a blown fuse? I've already made plans to take it to a tech tomorrow, but if it was something simple like a fuse, i wanted to at least try. The last time i had an issue it went completely, no power light, nothing. Any ideas?