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Model A1419 / Late 2013 / 3.2 & 3.4 GHz Core i5 or 3.5 GHz Core i7 Processor, ID iMac14,2

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iMac 27 inch late-2013 not starting up after upgrades

Hi all,

for the first time today I opened my iMac 27" late-2013 to upgrade to an NVME M.2 drive, and also to switch to a i7-4771 CPU, I followed all the procedures correctly, but now my iMac won't startup. I get 3 beeps followed by a 5-second interval, and it repeats. I understand this is due to the RAM not passing checkup or not being recognized. I reseated the 32Mo, but still the same thing...

PS: If the CPU was bad, it wouldn't even try to check the RAM, right??

Any ideas would be very helpful and appreciated.

Thank You

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I would reduce your RAM down to the original RAM to see if the system finishes POST. Then swap it out to 16GB, then swap out this set putting in the other 16GB into the same slots, now after that’s working plug in the first set into the empty slots. Let us know how it goes.

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I removed 2x8Go, and even down to one 8Go, same thing….

I haven’t tried yet, but I doubt clearing the NVRAM will help if it’s not even finishing posting…


@neve1 - Did you go back to the RAM the system had before you upgraded? Also did you properly install the RAM into the correct slots? The slots the RAM was in is the same slots you need to populate first.

Lastly, make sure you’ve pressed the SO-DIMMs fully in.


Hi Dan,

Yes I did. The RAM is well seated and installed correctly. I did it several times.

I turned on the iMac without the screen on to check the LED's.

When the power cable is connected, the bottom LED (#1) in on as expected. When I press the power button, LED #2 turns on, and I get immediately the 3 beeps, followed by a 5 sec interval, et it repeats.

According to Apple: "The memory in your Mac didn't pass an integrity check. If you added or replaced memory, make sure that it's properly installed."

My question is: Could this be an issue with the CPU or the socket?

Since it apparently starts posting, it seems to me that the CPU and/or socket are ok, or am I mistaken?

I understand that if the socket is damaged, the board is essentially toast. I hope this is not the case.



@neve1 - mmm… I guess it’s possible the CPU socket pins got damaged in the process of your Chip swap-out. I mostly find the system won’t even POST (EFI boot) if the chip is not seated correctly. I would take the chip out at this point as that is the only place I can see in the memories data lines that could be messed up.


That's what I'm afraid of. I hope that's not the case or that it's not too bad.

I was trying to avoid taking the board out again. But it seems I don't have another choice at this point. I'll do that tomorrow. It's kinda late on my side of the pond. I'll post results as soon as I can.



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