Model A1224 / Mid 2007 and Early 2008 / 2, 2.4, or 2.66 GHz Core 2 Duo processor

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Why is my iMac powering off or not starting at all?

Hi there,

After replacing RAM and installing the latest version of OS X on my 20" iMac, I used it. After a day, it didn't boot anymore. I unplugged the power adaptor, waited a few seconds and then tried again. Sometimes the iMac does start up, but in general it does not. When it does not start up, I can hear something inside turning (I don't know what it is). After a while, the sound stops. When I unplug the adapter, it works (sometimes).

I thought it might be a software problem, because it worked sometimes, so I tried re-installing OS X. All the time, during the process of installing, the iMac powered off again. It just completely shuts down out of nothing.

Today, I connected a firewire cable and I installed a new version of OS X trough another computer. This worked. The iMac booted, OS X started but after less then five minutes, the iMac shut itself down. I would very much like to know what problem could be causing this and how can I fix it?

Looking forward to hearing from you. If you need more information, please let me know and I will respond as soon as possible.

Thanks in advance,


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Go over all your connectors again...

Recheck the RAM - try one module at a time, switch banks, go back to the old RAM.

Run Apple Hardware Test or Apple Diagnostic test if possible.

If by "the latest version of X" you mean Mavericks or Yosemite go back to the rev that was working before. "Current OS X is pushing that box very hard, and, you're not getting full effect from using it anyway.

*This system can run the most recent version of OS X 10.9 "Mavericks" if upgraded to at least 2 GB of RAM. It is not supported booting into 64-bit mode when running Mac OS X 10.6 "Snow Leopard." It does not support OpenCL nor does it support AirDrop, AirPlay Mirroring (which also requires a 2nd Gen or later Apple TV), or Power Nap.

Please note that OS X "Lion" 10.7 and subsequent versions of OS X, like Mountain Lion and Mavericks, are not capable of running Mac OS X apps originally written for the PowerPC processor as these operating systems do not support the "Rosetta" environment. To run PowerPC applications on this Mac, it will be necessary to use Mac OS X 10.6 "Snow Leopard" or earlier.

If this answer is acceptable please remember to return and mark it.


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Thank you for your quick response. I have gone back to the old RAM (2GB). Now it seems to work fine (let's hope it will continue to work).

Does this mean that the RAM (4GB) I used was simply not compatible with the iMac? Because it should support 4 GB if I understood it correctly. Thank you for your help.

Only if the RAM are (667 MHz DDR2 SDRAM, PC2-5300) SO-DIMM modules.

*Apple officially supports 4 GB of RAM, but third-parties have been able to upgrade the system to 6 GB of RAM using one 2 GB and one 4 GB memory module.



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