Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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Won't power up after switching out HDD

I have a late 2015 iMac 27" 1TB Fusion Drive.

I switched out the Seagate 1TB HD with a Samsung 1TB SSD and also switched the apple 32GB PCIe blade SSD with a Samsung 128GB SSD.

Before replacing the LCD screen I turned the computer on at the mains (started up without pressing the power button). I proceeded to reinstall OSX Sierra from a USB Flash Drive, while this was going on I reattached the LCD screen. Once OS-X was reinstalled I then migrated my info from my backup disk. All was working fine.

I powered down my iMac but now it won't power back up. I've checked the power wire from the power button which is fine and connected correctly, there is 1 LED lit on the logic board when plugged into the mains and all connections appear intact and fitted correctly.

Any suggestions?

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1 Answer

Chosen Solution

To start with you'll need to pull the M.2 drive as Apple's driver won't support it. You'll need to install the custom Apple PCIe NVMe SSD drive.

Did you first break the Fusion Drive set? As you can't reuse the drives until you do. This also can effect things as the settings are also saved in NVRAM.

You can't create a Fusion Drive with with two SSD's as the OS is unable to deal with this config. You'll need to leave the system setup with two discreet drives.

You also need to install the in-line thermal sensor to replace the one that was in the HD you pulled. This is what you'll need: OWC - In-line Digital Thermal Sensor for Hard Drive Upgrade for 27" iMacs 2012 & Later

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The M.2 drive?

I didn't break the Fusion Set.

I can put the HDD back in if OS is unable to deal with x2 SSD config.

I have the thermal sensor you have referenced.



I hadn't quite finished things here (was interrupted) so do re-read it.

Here is what you'll need to break the Fusion Drive once you put both drives back: How to split up a Fusion Drive

What PCIe Drive did you put in? The proper Apple unit replacing the one your currently have or an M.2 unit (what Samsung sells directly)?


I've put the apple M.2 drive back in and replaced the 2.5" Samsung SSD with a seagate 2TB HDD, almost the original config, same problem, wont power up, 1 LED light on the logic board, could I have damaged either the logic board or the power unit?


You stated you re-connected the screen while the system was running is that correct? That could have damaged things.


The PCIe drive I put in was Samsung 128gb MZ-JPV1280/0A4 taken from a Macbook Pro 2015


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