Always read the f***ing manual. I did not. I had the amp in operation and switched the output power selector from 100w to 25w, then the switch arced, amp went silent and i blew some fuses and power tubes. I replaced said fuses and tubes but those tubes immediately blew as well. No warranty. From the schematics it looks likely to be an issue with the automatic bias control, the high voltage power supply, or maybe the output transformer. Anybody ever do this same stupid thing before? Any advice? Any ideas on how difficult or expensive it would be to fix this before I start unscrewing things and looking for burnt parts? Aaaaaand que the chorus of "Take it to a tech." Thanks talkbass.