While I'm certainly no electronic tech, I did see this SEVERAL times back in my music store days . . . basically, the amp fails, goes straight into DC, the speakers become heat sinks, and the paper cones light up. You get extra style points if the grill cloth follows suit while you're playing the encore, crowd goes crazy.
This happened to us in the store several times as a famous manufacturer was using a particular acid bath formula on their PC boards that evidently smelled just like the female of the species to a roach once the unit was warm. Roach would crawl in, scurry about the circuit board looking for love, inevitably put one leg on a hot lead and another on a ground and POOF, the output transistors would blow and the juice would go straight to the speakers and the aforementioned phenomenon would ensue. It actually became a factory update and a warranty claim they honored on the pre-change units.
J o e y
