Power supply fried but iFixed it!
A power cut during a rain storm occurred, and immediately the power tried to come back on five times over 10 seconds. Those brown outs and surges fried my 27" iMac late 2009 EMC 2374, even though it was connected to a cheap Belkin surge protector. All my other sensitive electronics connected to Panamax surge protectors made it through the disaster okay. Upon looking at the four diagnostic LEDs on the surface of my motherboard, I could see none lit up, telling me the power supply was shot according to the Apple Service Manual for that model.
The repair went very smoothly, thanks! That was mainly due to the excellent tutorials here, but also because I've been inside this computer five times over the years upgrading to an SSD, replacing an old DVD drive, and cleaning up dust.
Although I was concerned that the tutorial for replacing the power supply linked to a replacement that wasn't available, with more searching of the iFixit site I was able to locate the correct power supply on another page. I think it's linked below. Because of the hard work at labeling your parts for sale, I quickly saw it was for my EMC 2374. You guys shipped the part the same day, and what I got was an exact replacement for the power supply I removed. Nice! I only wish you would ship via FedEx instead of UPS because FedEx delivers on a Saturday at no extra cost.
Some iMacs from 2009 and 2010 have a V-Sync cable with a very poor quality connector on the end, which is a flat, reinforced end that exposes the wire contacts the way an iPhone Lightning cord has exposed contacts. The V-Sync cable's end is still flexible, unfortunately. The repair is difficult because inserting the end is hard due to the lack of angles you can get to it, the lack of room for your hand in there, that bad angle that tweezers are forced to use, the delicate nature of how the ribbon cable bends where the reinforcement stops, and the way the contacts on the ribbon cable tear away after repeated insertions. After working on my iMac five times, I only have two of the four contacts left on my V-Sync cable. Luckily I have no flicker, and it's okay for now.
The main LCD cable, which has about 24 pins in a metal connector and needs to be removed from the motherboard, has delicate plastic tabs that have to be squeezed to release the cable. It's not easy to effect a release without squeezing too hard, because you have no idea if you've squeezed it enough, and you are forced to squeeze-pull the cable. If you do squeeze too hard or at an angle, you will bend a plastic tab and dislodge it from is metal actuator. None of this happens in an area you can see while you work on it because the LCD display cable is too short to lift the display enough. With a bit of luck and working very slowly, you will get it off.
The power supply circuit board itself was simple to replace, just four screws and two connectors that are solid plastic and easy to work with. I let the computer sit for an hour unplugged before I worked on the power supply to be assured I wouldn't get shocked by residual power stored in the capacitors. The Apple Service Manual recommends waiting 2 to 3 minutes only.
I use two items to prop the display up and allow me to work with both hands removing cables. When I'm removing the first cable, the V-Sync cable, and have very little room, I use two rolls of electrical tape on their sides to prop it open an inch or so. When I go to work on the LCD display main cable, I prop the display open with chopsticks with the narrow end inserted in a screw hole.
My advice on the cables: go very slowly removing and inserting them. If it's not a perfect attempt, pull out, relax a bit, and try again. Don't expect to get it right on the first try. That's not your fail. It's the nature of the design. What we really need is a specialty tool for the V-Sync cable, a pair of dual beveled forceps, but you can only find single beveled, which most people call angled. Luckily Apple realized the cable was poor and redesigned it within a year.
Be sure to ground yourself and let the computer sit unplugged before working on it. A can of compressed air, a headlight, and a stool are your best friends.