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

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Three LEDs, no chime, odd static noise.

A friend of mine asked me to take a look at her old iMac (EMC2133). She said during a recent storm her neighborhood experienced a blackout. When this happened she wasn't home, her computer was turned off, and it was plugged into a (good quality) surge protector. When she returned home, her computer would no longer turn on.

I took off the front cover and had a peek. When plugged in, the first diagnostic LED lights up (as it should). Pushing the power button immediately lights up the second and third diagnostic LEDs. The fans kick in, the hard drive spins up, and the optical drive does its POST, but that's it. No startup chime, just a black screen.

The voltage on the power supply is in spec (measured w/multimeter), and connecting the iMac to a bench power supply doesn't yield any improvement so I'm pretty sure it's not the power supply.

One thing I did notice is, when the machine starts up there's a "staticy-clicky" noise coming from somewhere behind the motherboard, below the hard drive (almost in the exact center of the iMac). I made a video so you can hear it; it becomes really audible at 0:16. It is most definitely NOT the hard drive, optical drive, or fans making this noise. Video here:

Apple says the lack of a fourth LED means that the display panel isn't responding. I tried disconnecting it to see if it would come up "headless" but it doesn't. I also tried hooking up an external monitor (both with the original panel in place, and with the original panel disconnected) but that didn't help. Is there any way to test this theory without swapping out the panel?

Otherwise, what might this be? Others have suggested a bad GPU but LED 3 "indicates that the computer and the video card are communicating" according to Apple so that would imply that the GPU is operating correctly. Or, am I misunderstanding that? Apple says "(LED 3) will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement." But I have all three LEDs; only LED4 remains off.

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Does not sound good here ;-{

While the power connection was protected, its likely one of the USB, FireWire or Ethernet connections was the pathway for the surge to sneak in.

At this point I think you'll need to pull the logic board to see if anything is visibly burnt (if we are so lucky). I'm suspecting something on the backside got hit.

Here's a good set of images for reference:

Block Image


Block Image


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Kinda weird how the mobo looks like a pistol. Never noticed that before.

She did have a USB printer and scanner plugged in. They are both fine, no problems there; she's using them with another computer now.

-sigh- I really didn't want to do a full teardown, but I guess there's nothing for it now.


It's not too bad here's the IFIXIT guide you'll: iMac Intel 20" EMC 2133 and 2210 Logic Board Replacement


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