I was having issues with my iMac screen going black on me. It was not going to sleep just black. I did a lot of research and finally came to the conclusion that is was a bad power supply. We had done the resets that they recommend doing SMC and others no help so they determined that is was the power supply.
The repair went awesome because of the info I was able to get from ifixit. The tutorials were great made it so easy. It took maybe 30 minutes is all. Very easy. After installing the new power supply I hooked up the second monitor to the mac. About a half hour into using the computer it did the same thing it did before the fix. But this time I found that the computer was still on cause I could still work on the other screen, so to me it seems that I might be having a screen issue. Well back to the drawing board I guess.
Thanks to ifixit for the help and support.
If you have to do this repair ifixit makes it so easy. Just watch their tutorials and get the parts from them as well. They ship stuff fast.
The one thing I do have to say is make sure you hook up all the connectors back up I almost missed one.
Heavy-Duty Suction Cups (Pair)
iMac Intel 27" EMC 2309, 2374, 2390 or 2429 Power Supply