Model A1174 with 2 GHz Core Duo or Model A1207 with 2.16 or 2.33 GHz Core 2 Duo

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iMac Not Powering On; all 3 LEDs are unlit


I have a late 2006 iMac "Core 2 Duo" 2.16 20-Inch (A1207; last of white plastic models). It's been fine until today, but is suddenly powered off and won't turn on--no noise, lights, fans…nada.


- reset the SMC

- tried different power cords and outlets

- removed and reseated RAM

- opened it: none of 3 diagnostic LED lights are lit

At this point I'm assuming it's the power supply, but wanted to make sure before I buy another. Thanks!

- Mark -

Answer this question I have this problem too

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Here's how to do it: iMac Intel 20" EMC 2105 and 2118 Power Supply Replacement

Apple Part #: 661-3780

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Thanks, Mayer: I've seen your many posts on this topic. I just wanted to ensure it was the power supply before I replace it; I've actually done it before on another iMac.


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I have the same problem for exactly the same model. However, when I opened up and plugged the power cord, the first LED did light up. I unplugged the power cord and plugged it again, but this time the first LED did light up. Not sure if I assume the problem to be with the PSU or some other problem because of the fact that it turned on the first time. Please help.

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Correction - I meant to say the first LED did NOT light up subsequently


If you have exactly the same problem, the solution would be the same. Which you don't but the solution is still the same.


Please note that there is a variation to my problem in the sense the first LED turned on the first time but not after that. Can I assume this to be a PSU failure?


#1 LED will come on most of the even in a failed power supply. It means it is getting trickle power to it, not that it works. #2 will light if it works.


Thanks mayer. I'm pursuing the option of replacing the PSU. I opened up my iMac and got to the extent of removing the LCD screen. I took the shortcut (replacing PSU) route in your repair guides. However, I have hit some roadblocks. I'm unable to take out the bottom screw of the HDD bracket. It just keeps rotating but wouldn't come out. At the same time, I noticed that the HDD won't come out even if I manage to remove the screw as I notice that the HDD seems to be fixed on the other parallel side as well, perhaps screwed to the rear case frame or something. But I may be wrong. At this point, I'm thinking of removing the logic board (which I don't want to do as I'm not an expert and there seem to be lot of careful steps involved). Please advice. If my iMac works with replacing the PSU, I was hoping to upgrade my HDD as well. Please advice how to go about this. Thanks a lot for your help.


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bigmark will be eternally grateful.
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