I've posted other messages about output transistors, etc for this M4 and appreciate the help. This amp was working in service. I was testing some speakers and managed to short the wires which killed the amp and put the red overload light on. I replaced the bad left channel output transistors (with MJ21193/MJ21194), and two of the fusible resistors. Decided to do a full refresh and replaced all electrolytics, both relays, the main caps (upped to 22000uf, with a slight mod to structural plate to stabilize the larger main caps). Powered up to do adjustments and immediately blew a fuse. The amp has two fuse slots, and there are two manufacturer fuse sticker / labels next to them. If the stickers indicate position - the top should be 10A and the bottom 5A. Strangely the top fuse that blew was a 5A. Can anyone confirm correct position/value of these? It was working before so this shouldn't be related? (It's possible I switched them while cleaning but I don't think so. never say never) -checked to make sure I had all OT in proper locations. Check. -checked for solder bridges, board cracks. Check. -Will go back and check orientation of all caps. Is it possible to have killed the main transformer? Thoughts?