Replace non-booting Late 2014 27” iMac Power Supply, Save data from Fusion Drive, Upgrade to SSD Help?

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Level 1

4 points

Replace non-booting Late 2014 27” iMac Power Supply, Save data from Fusion Drive, Upgrade to SSD Help?

I had a wonderful Late 2014 27" 5K iMac that was working with OSX 10.10 Yosemite into Sept. 2022 that at first took very slow to boot up, then it started up with the Prohibitory (Circle with Line Symbol), and eventually stopped turning on. I intended to look into this when I had the time which is now.

It has been opened to see what the issue is. The 4 LED lights on the original Power

Supply Board don’t turn on, a replacement was bought. The internal drive is a 1TB Western Digital Drive (Western Digital Drives have a very bad track record and fail consistently, I avoid or replace them whenever

possible).

Since the iMac is open, I already bought an OWC 2TB SSD Upgrade with Thermal

Sensor Kit and plan to recover the data from the stock 1TB Western Digital internal drive. I was

told that for Fusion Drives, the Blade Drive is ‘linked’ to the 3.5” Platter

Drive so I’d like to recover that data from the drive, toss it out and replace with

an SSD since the computer is already open.

The drives were never encrypted, it was last running OSX

10.10/Yosemite around Sept. 2022 when it was last on and working, so hopefully

this helps. With regards to the SSD upgrades, is the OWC Mercury 2TB better

than a Samsung 840 Evo 2TB? I ask while there’s time to make a choice for the

replacement INTERNAL drive, the other can be used as an external backup Time

Machine Drive.

I’m told the best advice to use a USB cable to a bootable

external drive which can be done later. The iMac is already open and the

parts were bought so I’m going to put the components inside. Can I upgrade the blade

drive, if so, which ones are compatible with this model, and what advice is

recommended for what I’m planning on doing? I have already seen advice on using a bootable external, but I already have the parts necessary to put inside the machine.

The power supply also has large capacitors which is quite

dangerous, so I’d like to do everything in one shot (or as few steps as

feasible) to avoid injury or any risk to myself or the computer.

In Summary for this Opened Up Late 2014 5K 27" iMac To Repair/Replace/Upgrade:

Replace the Power Supply Board so it can turn on again to aid in recovery of the internal drive data

Recover the data from the non-bootable Fusion 3.5” Drive via a System Recovery via the internet (I think the blade drive needs to work in tandem with the platter 3.5” HDD since it is branded as a ‘Fusion Drive’ or I have to do something in Terminal to 'break apart' the pairing of them)

Once data recovery is complete, I plan to remove the 3.5” HDD and replace with a 2.5” SSD for good

If possible, I’d like to upgrade the Blade Drive (it is 128GB I believe) to a larger capacity one. Also I don’t know if it was the component which prevented the iMac from booting

What other advice should be applied (e.g. clean the speakers? Internal upgrades like fans, cables, or thermal paste, best way to seal it up to avoid the display glass breaking?) since I plan to upgrade the internal components and likely seal it up for the last time

The 1TB Western Digital (3.5") original internal drive that came with the computer has been removed, but I don't know if the data can be recovered or a reinstall of OSX 10.10 Yosemite can be done externally with another Apple device like a Macbook Pro or if it HAS to be with that Blade Drive still inside the iMac?

The computer will be used for teaching, music recording/production, as well as

general use for the home office.

Please let me know and thanks in advance! These iMacs are wonderful for their display and loud speakers so I'd like to give it some new life with an upgrade and recover the files from before.

Earlier Mac models

Posted on Aug 17, 2025 05:22 PM

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Answer 1

NGC1487 Author

Level 1

4 points

Aug 29, 2025 07:18 PM in response to HWTech

HWTech,

What should the next course of action be? I waited doing anything to ask for advice, sorry for the delay. How sure are you that the blade SSD has failed? I know it is 128GB but shows up as around 1.33GB, see my post on August 21st at 3:56AM with some of the stats. It says there are some files there too which is strange, my understanding is that when a drive fails it will show up as the original capacity with all free space, 0 files, etc. This leads me to believe there is something there and it could possibly be saved.

Would a Check Disk work? I read that people with a Prohibtory Symbol iMac do the following:

1.Restart computer

2 Hold Command and S key

3. Log in and in Terminal,

4. Type fsck -fy hit enter

5. type reboot

Would the above work?

Also, I've done that file recovery before with Macs (I think I used Stellar Phoenix) and got the files back with no file names, e.g. just numbered files in the past. If you have particular software that you know works best with Fusion Drives, let me know and I can look into them. That would be better than nothing, to be completely honest, but I'd like to see if a Check Disk or Internet Recovery could work?

Also, from what I can tell, when I log into Recovery Mode on that iMac with 10.10 Yosemite, it looks like there 'is' an option for Internet Recovery; if I were to try it and to reinstall the operating system, e.g. just with Command R so that it ONLY reinstalls Yosemite, which came stock when that machine was new (and never upgraded to El Capitan, Catalina, etc.), is it safe to do? With Command Option R I believe it will reinstall the operating system to the latest stable OS, which is what I'd prefer not to do, but if it can work, I'd be willing to try it.

If I do the above, which 'drive' do I select to reinstall the Operating System? Is it the Blade Drive, the 1000GB 3.5" Drive, or what? I ask since this is a 'Fusion Drive' and am unfamiliar with how the OS gets installed (or reinstalled) for these particular conventions.

How would I go about installing "macOS 10.13 and macOS 11.x" as you mentioned above?

My next question after all of this would be if I were to buy a brand new Blade Drive, which are compatible (I think they are Apple PCIe) and which are best for these machines? I'll have to open it back up again to take out the original Blade Drive (if it indeed has failed) and swap it with another one then put in the 2.5" HDD upgrade so I can seal it back up for good.

Thanks again for all the help thus far, I'm committed to get it back up and running, given that it is exciting that just swapping out the Power Supply Board got it to turn back on for the first time in a few years!

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Answer 2

HWTech

Level 9

66,674 points

Aug 30, 2025 12:21 PM in response to NGC1487

NGC1487 wrote:

HWTech,

What should the next course of action be? I waited doing anything to ask for advice, sorry for the delay.

I've already given you everything you need depending on the goal here. Which goal are you going for here?

How sure are you that the blade SSD has failed? I know it is 128GB but shows up as around 1.33GB,

Well, if the SSD is not always seen by the system, that is an indicator an SSD is failing.

Combined with the SSD reporting as 1.33GB......that shows the SSD has a problem, depending on how you got this information.

Would a Check Disk work? I read that people with a Prohibtory Symbol iMac do the following:

1.Restart computer

2 Hold Command and S key

3. Log in and in Terminal,

4. Type fsck -fy hit enter

5. type reboot

Would the above work?

That will only scan the boot drive. If it is the internal HD, then it depends if the HD is healthy or not. You are missing a step in there...Step #3.5 is to change the volume from mounted as read-only to read+write (I'm writing this from memory.....when booted into Single User Mode you will see all the commands needed to run fsck on the volume including the mount command):

mount  -uw  /

Also, I've done that file recovery before with Macs (I think I used Stellar Phoenix) and got the files back with no file names, e.g. just numbered files in the past. If you have particular software that you know works best with Fusion Drives, let me know and I can look into them. That would be better than nothing, to be completely honest, but I'd like to see if a Check Disk or Internet Recovery could work?

All data recovery apps behave the same way if a Deep Scan or Thorough Scan is used when recovering files from an Apple filesystem.

Also, from what I can tell, when I log into Recovery Mode on that iMac with 10.10 Yosemite, it looks like there 'is' an option for Internet Recovery; if I were to try it and to reinstall the operating system, e.g. just with Command R so that it ONLY reinstalls Yosemite, which came stock when that machine was new (and never upgraded to El Capitan, Catalina, etc.), is it safe to do? With Command Option R I believe it will reinstall the operating system to the latest stable OS, which is what I'd prefer not to do, but if it can work, I'd be willing to try it.

If macOS 10.13+ has never been installed, then you don't have Internet Recovery Mode. The firmware update included with installing macOS 10.13+ adds the Internet Recovery Mode feature to the Late-2009+ Macs.

If I do the above, which 'drive' do I select to reinstall the Operating System? Is it the Blade Drive, the 1000GB 3.5" Drive, or what? I ask since this is a 'Fusion Drive' and am unfamiliar with how the OS gets installed (or reinstalled) for these particular conventions.

How would I go about installing "macOS 10.13 and macOS 11.x" as you mentioned above?

To install macOS High Sierra for the first time requires an internal drive with a GUID partition and MacOS Extended (Journaled) file system. The drive can be completely empty. The macOS 10.13+ installers require a properly partitioned & formatted internal drive to stage the firmware update.

macOS 10.13+ can be installed to any drive, including an external drive as long as the above conditions are met.

My next question after all of this would be if I were to buy a brand new Blade Drive, which are compatible (I think they are Apple PCIe) and which are best for these machines? I'll have to open it back up again to take out the original Blade Drive (if it indeed has failed) and swap it with another one then put in the 2.5" HDD upgrade so I can seal it back up for good.

OWC provides a drop in replacement SSD which uses the Apple proprietary SSD connector. I do have to question why you want to go to such extremes on a 2014 iMac since it is very tricky removing & reinstalling the Logic Board.....there is a lot of risk to accidental damage.

Thanks again for all the help thus far, I'm committed to get it back up and running, given that it is exciting that just swapping out the Power Supply Board got it to turn back on for the first time in a few years!

Good to know the power supply resolved that problem.

If you need data from the Fusion DriveRun DriveDx on both internal drives and posting the complete text report here using the "Additional Text" icon which looks like a piece of paper. FYI, SSDs tend to fail by disappearing and not from actual errors, so a health report won't show anything wrong if that is the case. To run DriveDx does require you to be able to boot into a full macOS installation whether internal or external.

If data is not needed, then just replace the internal HD with your new SSD.

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Answer 3

NGC1487 Author

Level 1

4 points

Sep 1, 2025 04:19 AM in response to HWTech

HWTech wrote:

I've already given you everything you need depending on the goal here. Which goal are you going for here?

The goal is to get the computer back up and running, with at least an attempt to either repair the Fusion Drive for one last recovery/backup, then get rid of one, or both of the previous Fusion Drives to have a fully working iMac

How sure are you that the blade SSD has failed? I know it is 128GB but shows up as around 1.33GB,

Well, if the SSD is not always seen by the system, that is an indicator an SSD is failing.

Combined with the SSD reporting as 1.33GB......that shows the SSD has a problem, depending on how you got this information.

These are pictures from Command+R. The choices are Disk Utility and Reinstall OS X. If I choose Reinstall OS X, it shows a screen saying it can reinstall Yosemite 10.10 but I need Wifi to get on the internet; is this not like internet recovery? This was what I mentioned earlier.

For Disk Utility, please see the link containing the images, including when I select Reinstall OS X, it appears it may install the stock Yosemite 10.10 which came with the computer when it was brand new? If asked for a choice, what drive should it be installed to, but what should be expected since this was a Fusion Drive to begin with, so does this option know to 'fix' or reinstall the stock operating system without erasing my files, much like if you did this option for a Mac with a normal hard drive like an internal SATA drive?

DriveDxReport_APPLE HDD ST1000DM003_

Would a Check Disk work? I read that people with a Prohibtory Symbol iMac do the following:

1.Restart computer

2 Hold Command and S key

3. Log in and in Terminal,

4. Type fsck -fy hit enter

5. type reboot

Would the above work?

That will only scan the boot drive. If it is the internal HD, then it depends if the HD is healthy or not. You are missing a step in there...Step #3.5 is to change the volume from mounted as read-only to read+write (I'm writing this from memory.....when booted into Single User Mode you will see all the commands needed to run fsck on the volume including the mount command):

mount -uw /

So I add that command line you have there and it should read/write if necessary? Both drives, the blade SSD drive and the 3.5" Western Digital 1000GB are both internal.

If macOS 10.13+ has never been installed, then you don't have Internet Recovery Mode. The firmware update included with installing macOS 10.13+ adds the Internet Recovery Mode feature to the Late-2009+ Macs.

See above; especially this picture: https://i.imgur.com/jzW4tEI.jpeg I have Wifi, and I can connect the iMac with an ethernet cable if need be; it has that slot and I know wired internet would be safer to reinstall the OS without internet disconnection.

To install macOS High Sierra for the first time requires an internal drive with a GUID partition and MacOS Extended (Journaled) file system. The drive can be completely empty. The macOS 10.13+ installers require a properly partitioned & formatted internal drive to stage the firmware update.

macOS 10.13+ can be installed to any drive, including an external drive as long as the above conditions are met.

Can I take a blank 2.5" laptop SSHD I have and install 10.13 via an external drive connected to a working MacBook Pro or does the blank 2.5" laptop SSHD have to be put inside of the MacBook pro to install, if this is what you mean by specifically internally connected to the ribbon cable that connects it to the logic board

OWC provides a drop in replacement SSD which uses the Apple proprietary SSD connector. I do have to question why you want to go to such extremes on a 2014 iMac since it is very tricky removing & reinstalling the Logic Board.....there is a lot of risk to accidental damage.

I mentioned it previously; I am using audio engineering hardware and a Pro Tools Box that connects to the Firewire Port and works optimally on Mountain Lion to High Sierra. Also, let's just say 'if' that blade SSD drive is failing or could zap out? Wouldn't it be safest to remove a failing part from the board entirely, or could I really just leave it there, ignore it, take out the 3.5" 1000GB drive and just replace it with the 2.5" SSD OWC 2TB Mercury Electra 6G upgrade I still have and am waiting to decide if it is worth putting in or getting a better 2.5" SSD?

Good to know the power supply resolved that problem.

Since that worked, now I'm fully committed to get this working again.

If you need data from the Fusion DriveRun DriveDx on both internal drives and posting the complete text report here using the "Additional Text" icon which looks like a piece of paper. FYI, SSDs tend to fail by disappearing and not from actual errors, so a health report won't show anything wrong if that is the case.

Log attached. Please let me know if there is anything useful there which may help in resolving the issue of getting the original files back and deciding if its worth removing the blade drive to prevent it from affecting the other parts

DriveDxReport_APPLE HDD ST1000DM003_

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Answer 4

MartinR

Level 7

23,439 points

Sep 1, 2025 07:38 AM in response to NGC1487

Coming late to this party. Just wanted to make sure you are aware there is extensive repair information including detailed pictures & user experience on I FiX IT DOT COM

Look for iMac Intel 27" Retina 5K Display (Late 2014 & 2015) Repair

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

(link not provided because it would probably be removed).

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Answer 5

HWTech

Level 9

66,674 points

Sep 1, 2025 05:27 PM in response to NGC1487

NGC1487 wrote:

The goal is to get the computer back up and running, with at least an attempt to either repair the Fusion Drive for one last recovery/backup, then get rid of one, or both of the previous Fusion Drives to have a fully working iMac

FYI, there is no way to restore a split Fusion Drive and retain the data stored on the two physical drives which make up the Fusion Drive. macOS will either see the two physical drives as a Fusion Drive, or it will not.

Once data recovery is no longer on the table, then you can create a new Fusion Drive as long as both drives are healthy.

How sure are you that the blade SSD has failed? I know it is 128GB but shows up as around 1.33GB,

Well, if the SSD is not always seen by the system, that is an indicator an SSD is failing.

Combined with the SSD reporting as 1.33GB......that shows the SSD has a problem, depending on how you got this information.

These are pictures from Command+R. The choices are Disk Utility and Reinstall OS X. If I choose Reinstall OS X, it shows a screen saying it can reinstall Yosemite 10.10 but I need Wifi to get on the internet; is this not like internet recovery? This was what I mentioned earlier.

For Disk Utility, please see the link containing the images, including when I select Reinstall OS X, it appears it may install the stock Yosemite 10.10 which came with the computer when it was brand new? If asked for a choice, what drive should it be installed to, but what should be expected since this was a Fusion Drive to begin with, so does this option know to 'fix' or reinstall the stock operating system without erasing my files, much like if you did this option for a Mac with a normal hard drive like an internal SATA drive?

I'm surprised that the Yosemite installer is not showing the physical drives. I thought Disk Utility with Yosemite always showed the physical drives, but your pictures only show "Macintosh HD" in red on the left pane of Disk Utility indicating a broken volume....in this case a broken Fusion Drive.

Unfortunately Disk Utility is a terrible app. While booted in Recovery Mode launch the Terminal app from the "Utilities" menu on the menu bar. Issue the following command to display the drives & their layouts....it will pause the output once the screen is full....up & down arrows can scroll the output to see more and press "Q" to quit & exit back to the command prompt.

diskutil  list  |  less

Ignore any external or virtual volumes as they are associated with the installer & are irrelevant. Usually the internal physical drives & volumes will be the first items on the list, but a failing drive may show up later on the list. A picture of the first page of output should be sufficient unless you see the 120/128GB SSD listed, then include a picture of it as well. Please use the "Image Insertion" tool located on the forum editing toolbar so the images will remain available with this thread since outside links break very quickly.

<DriveDxReport_APPLE HDD ST1000DM003_.log>

The health report for the Hard Drive looks good, but it shows the drive is only connected as SATA II 3Gb/s when it should be a SATA III 6Gb/s connection. I guess the missing SSD could be the cause of it since the internal OEM SSD is SATA based. I'm assuming DriveDx did not see the 120/128GB Apple SSD?

mount -uw /

So I add that command line you have there and it should read/write if necessary? Both drives, the blade SSD drive and the 3.5" Western Digital 1000GB are both internal.

Yes...remember Single User Mode lists the commands needed so follow the on screen instructions.

Unfortunately if you are not booting to the internal drive you want to fix, then Single User Mode is irrelevant. From everything I've seen here you have a broken Fusion Drive with a bad SSD. If you are booting to the internal drive with Single User Mode, then I'm not sure how you are even doing that since I don't believe it is possible without having installed macOS onto the Hard Drive.

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Answer 6

HWTech

Level 9

66,674 points

Sep 1, 2025 05:28 PM in response to NGC1487

Continued....

If macOS 10.13+ has never been installed, then you don't have Internet Recovery Mode. The firmware update included with installing macOS 10.13+ adds the Internet Recovery Mode feature to the Late-2009+ Macs.

See above; especially this picture: https://i.imgur.com/jzW4tEI.jpeg I have Wifi, and I can connect the iMac with an ethernet cable if need be; it has that slot and I know wired internet would be safer to reinstall the OS without internet disconnection.

macOS 10.10 Yosemite is very old now & the Internet has changed. Perhaps Apple has changed access to their online servers.....assuming it is not a problem with actually authenticating with your WiFi's SSID. Apple has been breaking access to their older online installers for quite a while now.

Can I take a blank 2.5" laptop SSHD I have and install 10.13 via an external drive connected to a working MacBook Pro or does the blank 2.5" laptop SSHD have to be put inside of the MacBook pro to install, if this is what you mean by specifically internally connected to the ribbon cable that connects it to the logic board

macOS can be installed to an internal or external drive....it does not matter to the Apple hardware or OS. The other Mac must be compatible with High Sierra.

However, what good will this do you? In order to use a third party NVMe PCIe blade style internal SSD in the iMac requires installing macOS 10.13+ on that Mac so that Mac's firmware can be updated to understand both an NVMe internal SSD and the new (at that time) APFS file system used by macOS 10.13+, plus providing access to Internet Recovery Mode to access the online Big Sur online installer. Booting macOS 10.13 external SSD on your iMac won't work because that external drive will most likely be using the APFS file system which your iMac's system firmware will not understand.

If you have another Mac model generally from Late-2009 to 2018, then you can create a bootable macOS 10.13 USB installer which can be used on your iMac to install High Sierra onto an internal or external drive. Technically your 2014 iMac can run up to macOS 11.x Big Sur so that could allow you to have more options for creating a bootable macOS 11.x USB installer by having a Mac model up to Mid-2021.

Also, let's just say 'if' that blade SSD drive is failing or could zap out? Wouldn't it be safest to remove a failing part from the board entirely, or could I really just leave it there, ignore it, take out the 3.5" 1000GB drive and just replace it with the 2.5" SSD OWC 2TB Mercury Electra 6G upgrade I still have and am waiting to decide if it is worth putting in or getting a better 2.5" SSD?

If the internal blade SSD isn't causing problems, then I would ignore it. Unfortunately only you can tell or decide if that SSD is causing any problems.

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