iMac 21.5 Late 2012 - Stuck on Mountain Lion.

[Amsterdamned]

Ok, some context.

I purchased a very clean, cheap 21.5”, late 2012 i5 iMac with the intention of using it as a Windows PC. I have a couple of Mac minis and bought this one more as something to play around on, as opposed to using it as a daily driver, but wanted to get macOS working properly first before I started installing anything else.

The iMac is (was) running 10.8.5 but has the latest rom (showing as 292.00, from memory), so was running Catalina at some point. The problem I have now is that nothing I’ve tried so far will allow me to upgrade beyond Mountain Lion.

For example, a working, bootable Mojave USB installer gives me something along the lines of “...Mojave...is not supported on this type of Mac“, when I run it from the desktop, same story with High Sierra.

I can get to recovery but internet recovery only gets so far then the iMac shuts down. Booting from either of the USB installers I have produces the same end result; it shuts itself down. When it’s running, it doesn’t appear to have any issues and boots into safe mode without issue.

Would a Catalina USB installer work better? I’m currently downloading Catalina so will have that to hand in the morning. I’ve wiped the drive install but can get ML reinstalled via recovery.

I intended to open the iMac, to replace the internal drive with an SSD, so am open to any and all suggestions as I’m properly stumped.

 

[nambuccaheadsau]

Did you download the installers yourself and use say Diskmaker X to make the thumb drives bootable and have you checked on the OS Installer Certificates expiring? Have a read of thisd:-

Redownload Archived macOS Installers to Address Expired Certificates - TidBITS

Signing certificates for macOS installers have expired, so Apple consultants and IT admins who maintain troubleshooting toolkits containing older installers will need to download new copies.

tidbits.com

 

[Amsterdamned]

Did you download the installers yourself and use say Diskmaker X to make the thumb drives bootable and have you checked on the OS being outdated?

I downloaded them myself and used install disk creator, from Macdaddy.io. No issues as far as I can see. The outdated OS is the only thing I could think of. I did modify the system time but maybe didn’t get the correct date. When I get my hands on the Catalina installer and make it bootable I’ll try that and report back.

 

[chrfr]

I downloaded them myself and used install disk creator, from Macdaddy.io. No issues as far as I can see. The outdated OS is the only thing I could think of. I did modify the system time but maybe didn’t get the correct date. When I get my hands on the Catalina installer and make it bootable I’ll try that and report back.

I would try downloading the Catalina installer directly from Apple and try to upgrade from within Mountain Lion rather than bothering to try to make a USB installer. This may reveal more if there's an error about not being able to upgrade.

 

[DeltaMac]

According to eclecticlight, your 2012 iMac should have rom version 421.00 - so has not been updated from the most recent Catalina installer.
You probably cannot upgrade directly (in one step) from Mountain Lion to Catalina.
But, if you have a bootable installer, on an external drive, you should be able to boot to that installer, erase the internal drive, and do a clean install of whatever macOS system you want to install. At least, up to Catalina.

If you are opening up the iMac to replace the drive, consider upgrading the RAM, too. It's a bit of a job to remove the logic board (ram slots are on the back of that board) but worth doing if you already have it open.

The date adjustment really is not an issue now, if you have downloaded installers less than 6 months ago, but shouldn't hurt anything

 

[4sallypat]

My wife's 2012 iMac has Catalina so you should first get it to High Sierra and update to 10.13.6.
Once that is done, it's safe to go to Catalina.

 

[DeltaMac]

Current High Sierra installer app will give you 10.13.6. There would be a security update available for that, but no real reason to install that security update, if you would just be updating to Catalina from there.

 

[Amsterdamned]

The Catalina clean install (USB bootable) didn't work but (long error log I didn't get a chance to save), based on what @DeltaMac has said about the ROM version, it could be normal...maybe.

I'm reverting to a clean install of Mountain Lion, via recovery, so will try the High Sierra installer I have created from there and report back.

 

[Amsterdamned]

OK. Both High Sierra and Mojave get to almost the end of the coloured installation "line" then just go no further. They both get to the exact same point.

I downloaded both direct from Apple and both downloaded in less than a minute; my connection is nowhere near that fast so that's already a bit odd. Both HS and Mojave USB installers have the "no entry" symbol on them, when accessed via Finder, and both give an almost identical error when I try to run the installer from USB: "You can't open the application "Install macOS High Sierra" because it is not supported on this type of Mac". Similar message for Mojave and Catalina gives an error advising Catalina cannot be used to update ML - expected.

Currently downloading the full package for Yosemite so will see if that works.

Edit. I get "invalid checksum" when trying to open the Yosemite dmg. I've also tried copying the installer for HS from USB to applications and get the same "...not supported on this type of Mac" error.

Edit2. The downloaded package also gave the invalid checksum error when accessed via another Mac but I was able to download the same package (on that Mac) and it worked fine. I created a Yosemite USB installer but get the exact same issues as I did with the other versions.

 

[nambuccaheadsau]

Did you scroll down to the OS uploads on my Tidbits link? There are current down loads there OS X.10 to X.15.

 

[Amsterdamned]

Did you scroll down to the OS uploads on my Tidbits link? There are current down loads there OS X.10 to X.15.

All installers I've tried thus far came from links via apple:

How to download and install macOS – Apple Support (AU)

Download and install current or previous versions of the Mac operating system on compatible Mac computers.

support.apple.com

They work on other Macs just not this one.

I did try the Yosemite installer on boot (no clean install this time) and managed to get further than with others but still ended up with an error.

"An error occurred while extracting file from the package BaseSystemBinaries.pkg"

The end result is no more mountain lion but also no startup disk at all.

Edit. Trying a Yosemite install to an external SSD...gave me an error advising Yosemite couldn't be downloaded. Recovery partition has now been upgraded to Yosemite though which may have occurred earlier. It does want to "download and restore" OSX which sounds more like an internet recovery but it doesn't start like one.

Edit2. OK, I'm now stuck without an OS and unable to load one. However, I do have an install log from the failure I just had attempting to install Yosemite from a USB installers to external SSD. Does it mean anything to anyone? Tried to attach but it wasn't having it but can send to whoever wants to take a look.

Edit3. Dug out an old time machine backup disk which had both Catalina (pre 421.0.0.0 firmware) and Mojave backups on it. Booting from it and trying to restore from it in recovery ended up with a reboot...back into recovery. I've ordered the tools to get the iMac open and sealed up again so I'll also try to source a BR2032 logic board battery and maybe see if that helps. I'm loath to spend too much on it if the board's a goner but the fact that it was happy as Larry (-ish) on mountain lion suggests it can't be THAT bad.

Edit4. One thing I haven't mentioned is that I also can't get to diagnostics (holding down D on boot). Get an error: 0x800000000003, "Cannot load EFI/Drivers/TestSupport.efi" Status: 0x0000003. Anyone have ASD 3S152 to hand? I have a few but the newest is 3S143.

Edit5. (May 7th) Found and downloaded ASD 3S152. From the OS tests, I get T2ph sensor which is on the PSU. When testing the RAM, the system essentially crashed and rebooted into recovery. I have 16GB of compatible RAM coming next week, along with the tools/tape for the screen removal/reassembly. I'll check the PSU while I have it apart, as it could just be blocked exhaust ports etc. All other tests passed.

 

[Amsterdamned]

Took the iMac apart, cleaned everything, replaced the SSD with a Crucial MX500 (500GB) and 16GB of Timetec RAM. The T2ph sensor issue disappeared, probably because of all the dirt that was removed (compressed air fixed that). I took the fan apart and cleaned it completely. Very clever those maglev fans...not seen one before. I do have one additional sensor issue now but that's because the temp sensor from the original HDD is no longer there. No spinning fans though so I'm not bothered.

Now running Catalina with W10 boot camp and W8.1 (media center) under Hyper-V.

I'm waiting for some genuine Apple foam tape from the UK to finish it off but I did forget (twice) to check if the board had the slot for a blade drive. I'm not sure I can be bothered to take it all apart again, especially as it's unlikely (mine is fairly early in the production run). I have it set up the way I want it now and I'm using another SSD in a USB 3.0 caddy for TV storage so it's fine.

Removing the screen wasn't as bad as I'd feared either. I had one scare as I was about to start stripping the tape from the bottom of the screen; the display dropped into my hand! I'd placed my hand underneath and spread my fingers as wide as I could so I could hold it when I was working on that final bit of adhesive. Lucky!!

I quite fancy having a go at a 27" now

Have a great weekend all!!