iMac Intel 27". EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz), EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz)

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27" iMac suddenly won't turn on… completely dead? (late 2009 2309)

Model: Late 2009 iMac 27" A1312 2309 (Core 2 Duo)

Need some help please! I woke up one morning recently to find my iMac was dead to any input. It was working fine the night before, I didn't shut down and just let it go to sleep on it's own. There is zero response when the power button is pressed, no boot chime, no screen response, no fans/hard drives spin… nothing.

What I've tried so far:

  • Different power sockets, different power lead
  • Reset SMC
  • Replaced PRAM battery
  • Replaced iMac power supply
  • Removed graphics card

There is only one diagnostic led lit on the logic board (labelled LED601) when the iMac is plugged in:

Block Image

There are 4 LEDs in total and it's the led furthest from the board edge that lights up. Strangely the service manual for this model seems to list the LEDS in an opposite order to my board:

Block Image

I assume the LED that is lit up must be LED 1? ( indicating that trickle voltage from the power supply has been detected by the logic board).

Does this mean that it's most likely a logic board fail? why would the logic board suddenly fail overnight when iMac was sleeping?

Answer this question I have this problem too

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I have exactly the same problem; changed the power supply, but nothing.

Where can I find the diagnostic LEDs? So that I could have a check?

J. Willemsen

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The lights are to the right of the RAM slots on the logic board.

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How long did you hold the power button? Try keeping it depressed for about 1-2 minutes......

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Replace the power supply.

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I did that already, and it had no effect.

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Check the source of where that power supply came from. Sounds bad to me.

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Hello everyone. Just wanted to post what worked for me. I went through all the official mac steps, nothing worked. Dug deeper and found a "fix it yourself" step by step. It suggested pulling the RAM and then try starting the computer. This worked- The fans came on and the mac steadily beeped (indicating 'no RAM'). Now, one by one I replaced the 4 chips and started it up expecting to find a bad one that was causing my original problem. All 4 are back in and the mac is running just fine!?!? I hope this solution finds you. :0)

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@rudenator: YOU SAVED MY DAY (see below)

Thank you

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The "suddenly won't turn on" thing happened 2 times before throughout the years (I have it since late 2009...), so every time service would't find anything better than replacing the motherboard - which is f***ing expensive.

So I tried this time what @rudenator suggested, and YES !

In detail, all 4 memory slots were taken. Since some time, I had a doubt about it, as system diagnosis showed up only two ram in place. But so far the iMac worked fine, and I omitted to check physically if I was crazy or if the 2 ram had disappeared somehow.

In reality, the two "missing" memory bars seemed to be broken, and yes, they were still in place, they simply didn't show up. These two were in the BOTTOM emplacement. I took them out, as I guessed they were defective since a while.

Next I tried the two remaining individually in the TOP emplacement (relative to the screen which is top). This, because after Apple a single ram can work in the TOP place, but not in the bottom, at least for this model.

THE iMAC REBOOTED with one of them !

Next, I checked them all individually, and in fact even one of the former bottom ram still worked. YES.

I explain myself what happened, by the fact that if you pair a working with a non- working ram diagnosis thinks they are broken both, so if they are in bottom the machine don't shows them, and in top the machine won't boot.

I dont know, but maybe this trying saved me from a new motherboard...(which I wouldn't have paid, as the iMac is 8 years old now), but at least it saved me from buying new ram.

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Shane Murphy will be eternally grateful.
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