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Sudden Death of 2008 24" iMac

A

aubreyf

macrumors newbie
Original poster
Oct 31, 2012
5
0
Greetings!

Was operating my iMac a couple days ago, everything was perfectly normal, then it froze. (As I recall, I had a web browser and a couple Finder windows open. After waiting several minutes, I did a hard restart.

When powered on - iMac now chimes, shows the gray screen with the apple logo, and then shuts down. No failed HD icons or anything else.

FW Target Disk Mode doesn't help, shutdown occurs before boot options interface can appear, safe boot results in the following screen (which remains responsive): https://twitter.com/AubreyFalconer/status/263690927778971649/photo/1/large

Swapping both installed RAM sticks with a different set had no effect.

Model #: A1225

Would appreciate any ideas for what I should try next.
 
A failing video card doesn't cause the machine to not fully startup. A bad or failing hard drive could. Start your iMac up in verbose mode (Command-V after chime). What line does it repeat or freeze at?
 
Unfortunately, verbose mode doesn't display anything as the machine always powers down right before it has a chance to start describing things.

This machine has been behind a nice UPS all it's life, so I don't think a power surge could have burned out something on the mobo...
 
I'm hesitant to pull the screen because I'm afraid I'll never get all the dust particles perfectly cleaned off it again, but if I have run out of external diagnostic options, I suppose that would be the next step. Is there anything I could do inside other than swapping out the HD and then buying a new logic board (ouch!)?
 
Put in the reinstallation disc to see if it will boot from that. If it does you can install Mac OS X to an external drive.
 
If you can't get in to Verbose, I'm guessing you can't get in to Boot Manager (Option at chime). Have you tried SMC and NVRAM reset? If that fails, try the HDD first... (No need to remove the drive initially, just disconnect the SATA cables and try booting and see if you can get Boot Manager, or boot from alternate boot media.)
 
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"This machine has been behind a nice UPS all it's life, so I don't think a power surge could have burned out something on the mobo..."

Try DISCONNECTING the UPS, and plugging the iMac directly into the wall.

What happens now?
 
I had the same, but it started with crazy lines over the screen after 10 mins, then degenerated to apple logo and constant restart loop.
I sold it on to a friend for spares, he opened it up, blew an air duster over everything and it works perfectly now! It's worth a try!
 
Thanks all for your suggestions.

Already tried zapping the pram and running the iMac off several different power sources - exact same behavior.
I tried booting with a system dvd as well as a bootable flash drive - as suspected, shutdown before anything could happen.

I had never heard of a SMC reset, I'll try that right now.

I have experienced bizarre overheating behavior on tower PCs, so I already took a vacuum to the air intake and outlet ports of the iMac, but you might be on exactly the right track with the massive internal dust buildup theory.

I'll be sure to let everyone know how this turns out once I get inside.
 
Amazingly enough, this machine is now performing perfectly after the installation of a new hard drive.

Hope this is useful to anyone out there who experiences similar symptoms in the future.
 
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