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A2115 / 2019 / Processors from 3.0 GHz 6-core i5, up to 3.6 GHz 8-core i9. Released March 19, 2019.

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System not starting up black screen

I replaced my iMac's CPU and PCIe/NVMe SSD (i5-i9 and M.2 with adapter).

The unit turns on and hard drive spins together with the fan and there are two LED lights that turned on but when I install the Monitor, the monitor doesn't show anything (the monitor is also brand new because I need to replace the entire iMac screen due to broken glass panel). See image attached.

By the way, my unit is 2019 5k iMac.

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Update (10/12/23)

Hi. The situation worsened, after I put everything back (the original CPU and Blade SSD) only the second led is on and the rest of the four LEDs are off.

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I think you need to back off the Blade SSD for now and the onboard diagnostic LEDs are correct when you don’t have the display attached. Sadly this is a bit tricky! As you don’t have the extension cables to allow you to have the screen connected to the side. Without pulling on the cable and it’s connections see if the other LED comes on when the cables are connected.

You may need to remount the CPU as often that is the issue.

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Thanks, I will try this tomorrow and will provide an update.

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Hi, I took my unit to the repair center and it was found out that the CPU pins were bent. Upgrading the CPU is such a pain in the ass.

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Hi. Have same problem. I upgrade CPU and Blade SSD to SSD M.2. and now after turn on iMac i hear fan and on mothetboard to LEDs On: the 2nd and 3rd LED lights up and I see a black screen.

Does anyone have any idea what this could be?

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You might want to check that the CPU is seated correctly. Based on your problem, it seems like a CPU and/or GPU issue. Check to make sure that all power connectors and everything is in place, and then try it again. I had a problem similar to this a while back on a 21.5" iMac, and it turned out the CPU was faulty.

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M.2 SSDs often encounter issues with these adapters. I really don’t like using them in iMacs as it’s so much work to get to. I strongly recommend sticking with an Apple SSD or use ne of the direct pin compatible SSDs like OWC Aura SSD.

I’m suspecting the SSD is not making contact to the logic board if the CPU is correctly seated.

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