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

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

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.

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!