Recently my fiancee‘s iMac 24″ was having some issues. She had come back to the computer to find it frozen up, having to force-reboot. When the machine rebooted, it showed the feared “flashing question mark” icon, indicating the system could not find a usable/bootable OS on the machine. Inevitably, we ended up having to replace the drive.
I tried a lot of troubleshooting (including booting from my MacBook‘s drive using Firewire Target Disk Mode), but we determined it was entirely a physical problem with the hard drive. It would intermittently work for a short time, but eventually fail to work, causing a full system freeze.
After ~10 or so reboots we could get on the machine long enough to back up important data. Once the important stuff was backed up, I started the process of swapping the new drive in.
The previous drive was a nice 500gb SATA drive, so it was pretty rough that the drive has died after only 1 year and a couple months of usage. Unfortunately, that’s also 2 months outside of the standard 1-year warranty period. FTL!
I followed Octomac’s guide on swapping the drive, as well as checking a YouTube video (woot Fischerspooner) on the swap. Check those out if you want a good step by step explanation.
electrostatic discharge in 3.. 2..
Word of advice/caution: wear one of those anti-static wrist straps! When I first pulled off the front glass pane with a suction cup, it generated a TON of static electricity (so much that I could feel all the hair on my arm being pulled towards the glass). There was enough static electricity buildup that when I grabbed the glass with my hand, it shocked my finger so badly it was actually numb for 10 or 15 minutes. Ouch! I’m lucky the static discharge didn’t damage any of the computer electronics (damaged the nerves of my finger instead, I guess 
).
After removing the glass, there are 12 screws to remove, as well as the RAM slot cover underneath, so as to pull off the front aluminum cover. Pretty easy. During that process you also detatch a small cable that connects to what seems to be an ambient light sensor (or perhaps it’s the microphone? I don’t know). Pretty insane how small the iSight is, when you see it outside of the computer case.
LCD removed
After this, was probably the toughest part (although still pretty minimal complexity, nothing too tough). The actual LCD panel is attached to the iMac’s internal hardware via three different cables. I wasn’t sure what one of them does, but the other two are the DVI video connector and the other supplies power. It’s a good thing I had another set of hands to hold the LCD up while I detached these cables, as one is plugged into a circuit board that is mounted upside-down. Fun times.
new HD installed
The process of swapping the drive itself was quite simple. Pull off the thermal sensor from the drive (just sticks on with some glue stuff), unscrew two mounting screws, unplug the power/SATA cables, and pull out the drive. I tossed the other drive in (a nice new 1TB Seagate drive), and put everything back together. Remember to stick the thermal sensor onto your new drive! Pretty quick to put it all back together once you’ve taken it apart even once. :)
Next step was to boot up the machine and do a Leopard install. Everything started up fine, Disk Utility recognized the drive and had no issues formatting. Great! Installed Leopard and everything went perfectly. Success!
Honestly it was a lot easier than I expected – after hearing that you have to pull off the front glass, I was pretty concerned that it had some crazy glue or “sealing” process done. However, I was glad to learn that the glass is simply held on with magnets. Nice engineering! :) Another happy experience taking apart Apple hardware and seeing some really interesting hardware design/engineering techniques.
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Very cool. It’s always amazing to see how tightly and efficiently Apple engineers build these things.
Did you have any problems with getting dust on the other side of the glass?
Hi….your article is very helpful. May I ask what seagate model drive you replaced the old with. Is it fast, quiet, cool? Many thanks!
funny. I have the exact same problem with my imac 24″ and my conclusion is exactly the same, but I wonder if it is problem with sleep mode. Did the hard disk swap resolve your problem?
Thank you for your helpful article.
regards Niels
Yes, now that there’s the new hard drive, the computer is running perfectly. Nothing relating to sleep mode or anything.