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

Servant of Cats,

Thanks for the quick reply. Some time around Sept. 2022, the computer stopped turning on so I recently opened it up to see if it was the power button or something else; the culprit seems to be the Power Supply Board as none of the LEDs turned on despite there being power supplied to the machine.

I removed the SATA hard drive but never put it in a drive enclosure or anything else for fear of doing something destructive. There are backups of some (but not all) of the files and programs so I'd like to see if its possible to perhaps leave the Blade SSD in as it already is, put the SATA hard drive back, and replace the Power Supply Board, see if it turns on and then attempt a reinstall of OSX (I think perhaps it got corrupted over time?) with internet recovery.

Is this what I need to do before doing any of the upgrades to the hardware like the blade drive SSD in addition to the SSD 2.5" drive upgrade with the kit from OWC?

The other thing I'm having trouble understanding is when people talk about 'breaking' the Fusion drive; is that a command or series of commands in Terminal or is it merely by removing either/or, putting in new drive(s) and then reinstalling OSX via recovery or some other method?

HWTech,

Thanks for the reply and advice, I saw both posts, let's start with the first one because it looks like we're getting somewhere and honestly, I delayed doing these repairs because of any potential complications to the drive itself. I 'should' have attempted to reinstall OSX via Recovery when the iMac still turned on around and took very slow to get to the login screen around Summer/Fall 2022. After that, I switched over to a 2012 Macbook Pro and just ignored the iMac.

Around Summer 2024 I remember attempting to turn it on, I was involved in a move which was near the ocean/high humidity to another area that is dry, super low humidity. Someone in computer repairs told me that the environment alone can cause the Power Supply to fail, in addition to it being ~10 years old. Probably both factors to consider why it stopped turning on; the iMac Screen Adhesive has been cut (using a cutting tool supplied in the OWC iMac SSD Upgrade Kit) and the glass display folds up giving me access to seeing the inside; indeed all 4 LED lights don't turn on, on the Power Supply Board so I bought a replacement one for about ~$50 a few months ago.

My big worry is that no power has been supplied to the new board, nor has it been connected and I see and hear lots of warnings about major electric shock or death with this Power Supply, in addition to the visibly huge capacitors. This has deterred me from attempting anything so far.

HWTech wrote:

The PRAM battery may be a problem as well. Unfortunately on some iMacs, this battery is on the back side of the Logic Board. I honestly don't know if it would prevent the power LED from lighting up on the MLB, but it could definitely affect the power on & boot process (rare, but it does happen).

Yes, for this model (Late 2014 iMac 27"), the battery is a 2032, I have replacements but I haven't attempted to go any further than just removing the left speaker, 3.5" Hard Drive and carriage slot, and the Power Supply (since it more than likely is the culprit why it doesn't turn on).

HWTech wrote:

I would leave the original drives installed until you have finished trying to recover data from the Fusion Drive. This is the safest option. Theoretically it may be possible to remove both drives and access them externally on another Mac, but this is very risky since so much can go wrong if macOS does not recognize both drives in a timely manner which would result in a broken Fusion Drive.

Since the last time the iMac was powered on was in Sept. 2022, hopefully the computer doesn't know that the 3.5" HDD has been removed and will just be reconnected and the mount screwed back in. I've never heard of the computer not turning on 'breaking' the Fusion Drive, however my understanding is very limited about them, other than there is a blade drive component working in tandem with the (stock) 3.5" Western Digital drives originally supplied via Apple.

The other information I read some time ago was that you had to 'break' the Fusion Drives by running some command lines in Terminal; I thought this was the only way it could be done, others say to just simply take the drives out (on a working computer), you're mentioning that time can also 'break' the Fusion Drives; so I'm learning about this as we go along.

HWTech wrote:

If there is no power, then that is completely separate from any drive related issues (it is rare that a hard drive will cause a no power issue).

A no power issue can be caused by the power supply, or the Logic Board, or by a tiny cable on the front of the power supply connecting the Power Supply & Logic Board. You could also have a poor fitting AC cord, bad AC Cord, or bad electrical outlet or power/surge strip. Disconnecting the display assembly would be Ok in order to see if it may be causing a power related issue.

Going with your advice, it will be trivial for me to put back the speaker, install the new Power Supply Board and connect the cable I suspect you mean; there is one that looks like a large ATX-style cable end that clips onto the connection socket and then I remember a smaller one, possibly square shaped. One of the two was a pain to disconnect as I was worried about getting electric shock not knowing if the capacitors had fully discharged.

Since I will attempt this likely in a few hours after reading advice on this thread, are there any 'do's and don'ts' for installing the new Power Supply Board with paying heed to not getting electric shock, given that I may have to take the board out again to get to the battery and/or the Blade Drive I'd like to replace? Some people said only handle the Power Supply Board by the edges only and never the Board itself (never touch the capacitors or the chips) by the black printed board part (without components) I've seen people on repair videos doing different things.

My workspace is on stone tile floor with a wooden coffee table, humidity hovers at 30% or even lower during the daytime and lots of static 'zapping' if I walk to carpet areas or touch the electric switches after walking on the carpet.

So I believe I am ready to proceed to turn the iMac back on and did a few checks;

I checked to see if the Power Button was somehow snapped/broken from connection; my original suspicion when it stopped powering on. There was no issue with it being loose or disconnected; as far as I could tell (without removing a screw connecting the wire to the button housing). I was told it was most likely the Power Supply since it was old and the difference in the humidity over time; we're about to see.

You were right, the 4 LEDs are on the Logic Board, my memory was incorrect and thought they were on the Power Supply Board. Either way, reconnecting the new Power Supply Board was a hassle in the sense that, I'm glad I asked for advice before turning it on; there really was no way to 'not' touch certain parts of the board given how rigid the Molex cables are to connect to the Logic Board. Further, when you have to screw the four T10 screws to keep it in the housing, you have to force it in by (unfortunately) having to touch parts of the board and check that the Molex clips are snapped on. I spent some time plugging and unplugging them to convince myself it is actually connected. If anyone reads this in the future, make SURE you do this repair with a plan in mind to avoid confusion, doubt, or injury! Many pictures were taken in the event of a short or a component going on if something can be seen in the before/after states!

I also had to take out the Left Speaker a few times so I could be sure that the speaker wire runs through the bottom notch, and the thin 2 pin power supply button cable that connects to the Power Supply Board wasn't interfering with the Left Speaker or anything else. I wiped down some of the minimal dust and used a microfiber cloth plus compressed air. The data and power cable to the monitor looked like no issues there as well.

The stock 3.5" Western Digital 1000GB Drive was put back in, the left metal brace was removed and the SATA cable was plugged back in, but there is no way the iMac can know it was removed as it hasn't had power since 2022. The original bottom adhesive is still on the screen so I can easily flip it open to access the interior in the event something goes wrong.

That said, I STILL haven't powered the iMac on just yet and would like advice before doing so;

• If there is a rush against time to save the data, my guess is to do Command+Option+R to get to Internet Recovery and (hopefully) reinstall OSX Yosemite (it was the original OS that came running on the machine and never upgraded and several of my Applications had to use older versions of OSX)

• To assist with the above, I found and tested a working Mac Keyboard and a wired Microsoft USB Optical Mouse on my Macbook Pro, as I don't know that Bluetooth will on the iMac will work in Recovery or if it has failed over time. The iMac came with a Bluetooth Magic Mouse and Magic Keyboard, I still have them, but I'm guessing wired is the way to go

• I had an issue with Internet Recovery attempting to reinstall High Sierra on my Macbook Pro because I think it doesn't correctly reach the actual server anymore; there is a fix in Internet Recovery to open Terminal and type/edit a command line to an https server and then a few more lines have to be executed so it goes to the right place; is this the same for Yosemite?

• If the OS reinstallation is successful and I can access the desktop, the plan is to use Time Machine or Carbon Copy Cloner to copy the OS and files to a brand new 1TB SSHD 2.5" Laptop Drive, unless there is a better option?

• Once the above is done, I can proceed with the removal (and disposal) of the 3.5" Drive and the SSD Blade Drive to install the 2.5" SSD and buy a better/higher capacity blade drive, or do I need to do anything to 'remove' that Fusion link between the two on the computer? However, how long do I need to wait before opening and disconnecting the Power Supply Board; it has some monster 450V and 150uF capacitors, I didn't see the resistors, but I'm guessing the initial voltage is 450V down to 120V in order to get the time to fully discharge the capacitors? https://mustcalculate.com/electronics/capacitorchargeanddischarge.php

NOW we're getting somewhere!! I spent today looking more into what the Fusion Drives actually do; they move the most used files over to the blade SSD so the machine appears to work faster, however both need to work in tandem. I knew the latter part.

I just turned on the machine and had masking tape hold up the screen to the back case while being put on top of a thick towel. A 2.5" SSD from a Macbook Pro (with El Capitan installed when I first bought it, but I took it out and just put my regular-use 2.5" so the El Capitan one is just for diagnostics and doesn't have use except for today) with Drive DX installed. I tested it out on the 2.5" SSD in the USB3 enclosure beforehand and booted into it with Option on my regular use Macbook Pro. When turned on, the chime came up, I propped open the screen, all 4 LED lights were on, success, it was just the Power Supply Board that failed, as suspected.

The iMac Loading Screen is all black, which I don't remember before; I thought it was all gray. I did nothing to see what happens; it stalled at about 20-25% of the progress bar, just before reaching the left edge of the Apple design, then it goes to a SOLID Prohibitory Symbol (I thought it used to flash on an all gray screen but this was Sept. 2022 last the machine was turning on).

I shut it down, plugged in the USB3 enclosure with El Capitan and DriveDX, pressed Option, but I got the same as the above; Prohibitory with no useful outcome. Another shut down and power up, this time with Command+R to get into Recovery, the mouse cursor was seen for the first time, it got into Recovery fine and asked if I wanted to Install or go to Disk Utility.

In Disk Utility, the 3.5" Western Digital 1TB shows up as all red 'Macintosh HD', when I click it, it says: "This Fusion Drive is missing a disk". Would you like to rebuild this Fusion Drive? Rebuilding will erase the following disks: (all blank in a window/nothing to select) with Ignore and Fix buttons below. I clicked Ignore. In the information box, it says the Capacity and Used is 999.35 GB, and Available is 0 bytes; e.g. the entire capacity of the disk. Type: Logical Volume Group, Disk Status: Offline.

Below that is the 512GB USB3 SSD and then there is a black divider bar with 'disk 1'. Capacity: 1.33 GB, Available: 31.3 MB, used 1.3 GB with 40,755 files, 13,708 folders. I remember the SSD Blade Drive (stock, I never removed it or even got to taking the logic board out) is 128 GB, when the iMac was operational, the disk would say the size was 1.12 TB; e.g. the 1000GB WD 3.5” drive and the 128GB SSD Blade Drive.

I went back to the Red Macintosh HD and clicked Verify Disk. There is a long log list I can provide if needed and pictures, but the significant messages are as follows:

Verifying partition map for "APPLE HDD ST1000DM003 Media" (in bold black)

Checking booter partition disk0s3

Verifying file system.

Checking Journaled HFS Plus volume.

Checking... (several lines down of various checks)

The volume Recovery HD appears to be OK. (in green)

disk0s2: Scan for Volume Headers

disk0s2: Scan for Disk Labels

Logical Volume Group (long string of letters/numbers) spans 2 devices

Incomplete or inconsistent CoreStorage Physical Volume set (in bold red)

Storage system check exit code is 1.

Problems were found with the partition map which might prevent booting

Error: This disk needs to be repaired. Click Repair Disk. (in red)

I was able to choose the boot disk upon restart, so I chose the USB3 drive with El Capitan and DriveDX. It booted successfully with clunky sounds, not sure why but either a key was stuck and there were lots of characters on the login password. I removed with the mouse click and backspace.

DriveDX shows the Overall Health Rating, Overall Performance Rating as 99.1%, Advanced S.M.A.R.T. Status OK with 0 issues found. Total LBAs written 3.7TB (so I'm guessing the data is still there if it has some record of information?) Everything is just about all green with the exception fo Airflow Temperature Celsius (id 190) Current: 66, Worst 53, Threshold 45 and it is Neon Yellow at 38% but says OK. I also saved the output .txt log file if there is something specific there we need to check out.

Before proceeding doing anything, and especially since this is a Fusion Drive with possibility to lose or break things, please let me know how to proceed to save everything, possibly Repair or do something so I can access the files to save/back up and then get rid of the drives and replace.

I just shut everything down and didn't attempt any Repair/First Aid/reinstalling OS, etc. as I want to make sure to do things in the right order, on the right drive(s) and still is the outstanding issue of the SSD Blade Drive not showing up with the actual space it should be. If the OS has to be reinstalled, does that happen on the Blade Drive or on the 3.5" Drive? Please let me know and again, thanks for all the help thus far in the thread!

Rkauffman87 and Old Toad,

Thanks for the advice but please see the original post; I want to restore this iMac (it was my assigned work computer bought brand new by the job when I first started it) for the (new) purpose of making and recording music and general purpose home office stuff and media; the speakers are wonderful as is the display. Besides music, some of the work software I was using on it very specifically needed to be on Yosemite so that is why I never upgraded it beyond the very last update to OSX 10.10, I remember my office mates saying that the upgrade to El Capitan broke their stuff.

With the music production, I have older physical hardware such as AVID Pro Tools boxes

that require Firewire and older operating systems. The ‘sweet spot’ were the Mac

Operating Systems between Snow Leopard and High Sierra. Mavericks was the best

one to be absolutely honest especially with music stuff. Catalina was absolute garbage

and broke so many things; I don’t care for the newer operating systems, plus everything is

force-feeding AI to the customers, also of which I have zero interest in. It would be great to also

have an AI-free computer.

I also don’t mind to upgrade the Blade SSD to something like High Sierra or

Mojave, especially if it means I can buy the 3rd party Blade SSDs

with the faster speeds and not be limited to the ~550 MB/s for the 2.5” SSD

drives. I have a brand new 2TB 2.5” Samsung Evo SSD and the 2TB OWC Mercury

Electra 6G SSD (from the upgrade kit) which I am contemplating on replacing in

the iMac drive slot and then possibly going with one of the compatible PCIe

blade drives for iMacs that boast higher speeds than the 2.5” drives if memory

serves me right

I got this iMac for free from an old job that told me to just take it when it ended.

Because I was going to copy my files and replace the drives for security, I

spent maybe $150 for the SSD upgrade kit intended for the new user so I don’t

consider that to be a loss, just an operational cost/expenditure. I did spend

$50 for the brand new Power Supply Board.

Also, I like the satisfaction of the knowledge and repairing these older Macs,

despite how difficult some people say they are; the older modular stuff was the

best. I've fully tore down some of the unibody Macbook Pros and an iPhone 4 which were

definitely challenging, but good experiences to building confidence in understanding and repair.

I might steer towards the newer iMacs if after getting back into music

recording and engineering I find newer (likely full-on digital) software that

is only available with modern operating systems and the faster chips/processors.