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

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Why does my screen go gray

iMac 20" A1224 (EMC 2133)

At start up my monitor has vertical lines in red, yellow & gray.

When it gets to the point where the sign in screen should show, the screen turns gray.

I had to force it to shut down with the power button.

Any idea what it is? How do I repair the problem?

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Your systems specs: iMac 20" 2.4 GHz Core 2 Duo


I have the part. Just need to replace it.


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Hook it up to an external monitor and tell us your results.

UPDATE 8/7/17

Your problem is most likely the GPU (video card) It can be replaced. 70% of the time a reflow of the video card has fixed it in my experience.

We have to be careful with costs on a 10 year old machine, but with some effort this can still be a very serviceable machine.

Let's get that external monitor result and we can then look at our options.

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Almost all iMacs have the capability to attach an external monitor by plugging the appropriate cable into the back. Most likely the video card (or chip) in your iMac is damaged. You can test this by using a borrowed external monitor.

The port for your iMac is likely a "Mini-DVI". It would require an adapter to take it to VGA (the most common external monitor type...easily available from a Mac dealer). Connect the monitor's VGA cable to the VGA end of your adapter. Turn both devices on. If you see the iMac info on the monitor then you know that your iMac's video card is likely ok. It might if you don't see anything on the external then use two keys to switch between. The most common set of keys is Command key (held down) and the F-1 key (pressed and released). Basically you are turning MIRROR mode on and OFF with these keys. If you get no response from either switch then you probably have a video card or motherboard issue. And your iMac is too old to bother spending money on either.


Lost great comment while moving, we are trying to get it back up @addison


My son has a monitor for his hp. It's an hp monitor for an hp pc. Will that work? Otherwise we only have a MacBook Pro.


Well that's nice. I can't afford to buy a new Mac, so repair it is.


Sure any monitor will work, you will however, have to have the correct adapter.


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