iMac Blackscreen

in Current Mac Hardware

Hello everyone,

I am a french Canadian from Quebec, so sorry if my english isn't that good.

I own a 2017 iMac 21.5 inch, A1418  MNDY2LL/A model. 

I've recently got an blackscreen problem. The issue occurs on a strange way. 

When I say blackscreen, I mean that nothing is responding on the iMac and the screen is black. Even the 10 second reset with the power button doesn't work. I have to unplug it. 

When the iMac is freshly running after a day off, it can take about 3 to 4 hours before getting a first blackscreen.  After getting it, and a complete reboot, the next one will occur about an hour after.  After it, it become really unstable and the blackscreen can occur almost any time.

I tought it could be the HDD that had a problem, so I changed it for a brand new SSD HDD. But the blackscreen still comes during the download page of the iOS at the installation setup page. So I guess the HDD wasn't the problem. 

So now, I am turning over forum to see if any of you could have an idea, before putting the iMac for sales for parts. 

Any advice would be welcome.

Thank you.


  • Reply 1 of 1
    I would lean toward an issue with the power management controller... which is built into the main board... would require a complete new "motherboard" (to use an old term :) ).
    Of course, I'd recommend having Apple diagnose it properly... even though that will likely require leaving it at a store for a few days.

    I also considered a video output issue.. but... the lack of power-button-reset functionality leads me to think the PMC is more likely.

    Good luck!
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