Following a brief power fluctuation my mother's iMac was dead...black screen, no sound...dead. The cost of replacing it with a remanufactured Mac or new PC was more than she could easily afford, and her documents etc. on her dead Mac would entail disassembly of the iMac so as to retrieve the hard drive, so we determined to try to merely replace the power supply.
I've replaced many a power supply in PC's, which is a 10-15 minute fix. Not so with the iMac. Luckily ifixit had detailed (and invaluable) photos and text to describe the process. Halfway thru I was momentarily stymied by the fact that I did not have a magnetic, long & thin shaft 10mm Torx, so I had to go all barbarian and tear deep V's thru the case plastic so as to remove the 4 screws holding the monitor screen in. It didn't look pretty, but it worked. After reassembly it worked perfectly, and there was no visible trace of the gouges into the case I'd made...and Mom was ecstatic to get her iMac back in working condition with all of her documents and pictures intact.
Peeling the sticky EMI shield from around the monitor was a chore. Having a magnetic 10mm Torx with a long thin shaft was pretty much a neccessity to remove the 4 screws holding the monitor in (Step 12 in the instructions) unless you're willing to spend the 30 mins or so it takes to tear deep grooves thru the plastic. Unless you're experienced at iMac repair, the detailed instructions on ifixit were absolutely necessary.