I have read all I can find to no avail and am a newbee at this. My 771 was going along great, no issue that I am aware of and it stopped dead in it's tracks with no warning. No power at all. No smells, no buzz, no sound issues , no nothing. Am driving a pair of Pioneer CS99A's. I suspected a fuse and finally found a blown 5A fuse wired in between the normal 5 amp fuse in the back and the power transformer. It was encased in a clear plastic tube. ( not on schematic that I can see?). All other 8 power board fuses and the main power fuse look ok. I replaced this "wired up" unit with a normal fuse holder, replaced the std. 5A fuse and turned it on. It blew immediately. So much for simply an aging fuse. I now suspect a bad power transformer or a direct short somewhere but in that there were no issues up front to begin with this doesn't sound right. Switch seems to be ok as the switched main output works fine. No "obvious" issues on the power board or driver board or elsewhere. Main transformer? Output transistor? I need some ideas & guidance asap please.