Okay, not a real war--my iMac has not accompanied me on any of my sojourns to Iraq. However, I am an instructor at a military school and my iMac is key to my ability to Photoshop maps and news articles in order to put my students in fictitious wars around the world. I came in off the Christmas holiday break and found that my 2008 iMac 24" (EMC 2211) would not power up. I was heartbroken to say the least. I have a government computer (Windows) but can't install any of my own software and so wouldn't have key tools for doing my job. I tried swapping power cords, trying a different outlet, removing and reinstalling the RAM--you name it, I tried it. Unsure of whether it might be the power supply or the logic board (after Googling to see what the common causes of this problem were), I went to see the folks at the Genius Bar, only to be told that they couldn't do any repair work on it and therefore couldn't really tell me what the problem was. So I decided to try the power supply repair, since it seemed most likely and was cheaper than the logic board (a logic board repair would probably have caused me to replace it instead).
The repair was slow--but only because I had to wait several days for the replacement power supply to come in (the lingering effects of the holiday shipping surge). iFixit hadn't had the part on hand, so I went through Galaxy Hardware (galaxyhp.com) for the replacement part. Since I had my new Pro Tech Toolkit (which did arrive very quickly thanks to iFixit's speedy shipping), I decided to do the disassembly work anyway. This gave me the opportunity to clean the inside of the machine and to see if I could diagnose the problem even before the part arrived. Disassembly, using the Hard Drive replacement guide for the general steps and iFixit's supplement for removing the power supply, made the process easy. Since I had the iMac open, I was able to reconnect the power, right after getting the glass and bezel off, to check the diagnostic LEDs. No lights at all, which I guess could still have been either because of a bad power supply or a REALLY bad logic board, but that gave me confidence that I was on the right track. The toughest part was removing the LCD panel power ribbon cable from the bottom of the power supply, but an extra set of hands (provided by my lovely wife) helped steady the panel while I wrestled the cable. Once everything, including the old power supply, was removed, I gently vacuumed out all of the dust, and then replaced the bezel (with only a couple of screws) and the glass. When my part came in a few days later, I was able to install the new power supply and reassemble the iMac in only 30 min or so. I noticed immediately that the new power supply was a bit different than the old. While the old power supply had two heat sinks along its left-side edge, the new one did not. The package did, however, contain a rubber block that screwed into place and channeled the air that would have flowed over these two heat sinks back under the rest of the power supply. Before replacing the bezel and glass, I hooked up the power and, lo and behold, I had that magic diagnostic LED showing that the power supply was working. Let there be light! Let there be Joy!!
You definitely need a second set of hands to handle the LCD panel while you disconnect the LCD power ribbon cable. If you lift the panel and set it on its left edge just above the iMac (assuming you have the iMac laying on its back) you should have enough slack in the ribbon to be able to remove the four screws holding the power supply in place so that you can lift it and THEN remove the power cable to the LCD. I didn't try this during disassembly, but I did leave the power supply loose while I reconnected the LCD power cable and then screwed it into place. I can't imagine reconnected that ribbon cable after the power supply had been screwed down.