First timer but iFixit made it easy
30 Minuten - 1 Stunde
My 20" iMac simply stopped working one evening recently while I was streaming music to my Apple TV. I did a little research and found there were diagnostic lights on the bottom. I saw light #1 (which indicates if the unit is getting power) was blinking and "guessed" the power supply had gone bad. I ordered a replacement from iFixit and it arrived 2 days later. I also ordered the suction cups after watching a repair tutorial on the website and finding I needed them to remove the screen.
I followed the iFixit instructions to the letter and they were completely accurate. Impressive! The problem was diagnosed correctly and my iMac works great! Anyone can do this if you have just a little confidence and you follow the instructions.
My only problem with the process was removing a very tiny wire plugged into the power supply at the top (temperature sensor wire). This was so small and so tight (as the instructions indicated) that I could not remove it with my fingers. I tried using small needle nose pliers but the wire pulled out and the plug broke. I found a way to reattach the wire to the new power supply but it was not perfect.
It's nice to have someone help hold the monitor while you unplug some of the wires. It's also helpful if you find a way to keep track of which screws go where so you can put them back easily.
I found the instructions stopped after the new power supply was in place and they did not guide me through the reassembly process. However, it was easy to simply go backwards through the photos and instructions to make sure I put everything back where it belonged. Also, as I indicated above, be careful trying to remove the temperature sensor wire. Other than that, nothing to it. Thanks iFixit for all the great advice and instructions.