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Model A1418 / Early 2013 / 3.3 GHz Core i3 Processor / Education only model

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iMac startup but nothing on the display...


I’ve got an iMac 21,5” from Early 2013.

When I press the power button, I can hear the fan spinning and I hear the startup chime, but it doesn’t show anything on the screen.

I’ve tested it and the display panel is good, this isn’t something that’s wrong with the software and it can’t be the GPU because I’ve replaced the CPU (it only has integrated graphics) and it still doesn’t display anything… It’s not the RAM, the disk drive, the display nor the power supply.

The fan doesn’t speed up to the max and the only LED’s on the Logic Board that are on are the lower two LED’s.

I’m kind of getting lost with this iMac… I hope someone is able to help or has some advise…

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What was the condition of the system when you started? What this working before you opened it up and all you've done is replace the CPU?

If that is correct what is the CPU you put in?

Remember not all of the Intel CPU's have the intergraded graphics engine and you are limited on which CPU's you can put in.


@danj The iMac is second hand and this is what it does since the point I've got it. The CPU I've tried was a i7 3770.


Btw, the iMac doesn't even display anything on a external monitor over Mini DisplayPort, but as I said, it's not the CPU/ GPU (also because it does post), so maybe it's something from GPU to display connector? I really don't know...


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This system is only able to support an Intel Core i7-4770S Haswell

The Intel Core i7-3770 Ivy Bridge is not workable as the systems BIOS (EFI firmware) does not offer the needed microcode for it.

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So you're suggesting that it could still be the GPU in the CPU but I didn't troubleshoot it because the test CPU isn't supported? How did you find that out?


Knowing which CPU a given system supports just requires looking it up on EveryMac - Lookup clicking on the given system type and finding the series.

As far as knowing whats wrong, all I can do is make sure we have the system configured correctly and then troubleshoot if from there.

If you still have the original i3 CPU it come with I would put that back in and then check things again.


@danj Oh I thought I had researched it and that it would support the CPU that I’ve tried. I have the original i3 CPU and the problems started with that one. It’s not that I tried to upgrade it and that I broke it, it was broken and I tried to fix it with the i7. The i3 is currently installed and it posts (chimes) but doesn’t show anything on the internal or external monitor...


OK, thats useful to know! That sounds like you have a PCH issue!

It's time for a new logic board ;-{


@danj You think? Because the facts now are: I have an iMac that seems to startup, but doesn’t show any graphics. It has no graphics with 2 CPU’s of which one isn’t even supported by the machine. So we don’t know it’s not the integrated graphics and so the CPU right? It still could be that the i3 is broken because the used i7 couldn’t troubleshoot it. Do you understand what I’m trying to say?


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Max sera éternellement reconnaissant.
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