Aporte original por: info251 ,
Logic board schematics and testing procedures needed
I've inherited a "fried" imac from a friend. The machine was reportedly hit by a power surge from lightning although a surge protector was used. The machine will not power on, no boot chime, etc. I have reset SMC and the fans kick on in high speed but machine will not boot. I took apart the machine and inspected the logic board for burns, etc. and could find nothing. Replaced the RAM; nothing. Power supply tests out fine and I even replaced with a new unit; no change. On the logic board, I get LED#1 when the machine is plugged in, but when switched on, no other lights ever light up. I can get the fans to come on at high speed, the hdd and cd drives sound like they're getting power. My question is; I see all of these logic board repair services out there, what are they normally fixing and where are they getting their schematics etc from? This is not my everyday computer so it's kind of a hobby project at this point. Ultimately, if I cant fix it, I will probably have a pro get it going, but I would like to give it a shot.
iMac Intel 20" EMC 2266