Monterey semi-bricked Mac mini 2018

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Level 6

14,634 points

Monterey semi-bricked Mac mini 2018

FYI. I hope this helps someone.

I do not usually install a new macOS release to a main internal disk. But I had successfully tested my mission critical software on an external Monterey HDD for a week. AFAIK Monterey should be a smallish upgrade to Big Sur and I had some spare time so I did a clean Monterey install to the main internal SSD.

Monterey worked fine for a week until, coincidence or not, after a routine SMC & PRAM reset it booted only to a black screen (Thunderbolt LG Ultrafine 4K).

(Three years ago Mojave booted to a black Recovery or Safe mode screen until I noticed that re-connecting the Thunderbolt cable fixed the black screen. This was fixed a few months later via a Mojave firmware update. But now the screen remained black no matter what Thunderbolt port I used.)

I borrowed a newish MacBook Pro and used Apple Configurator 2 to Revive, and when that did not fix it, to Restore the Mac mini but the problem persisted.

https://support.apple.com/en-us/guide/apple-configurator-2/apdebea5be51/mac

This took me a few hours and it was getting dark outside ... and I then noticed that the screen was not completely black but it _very_ faintly showed Apple logo and then the spinning Internet Recovery globe. But even in a completely dark room I could not use the almost black user interface. Screen brightness did not respond to the now-wired Keyboard controls (I had also switched to a wired mouse by then).

I then connected the Mac to a TV via HDMI, and there the display worked as expected. The Restore had wiped the SSD data and apparently also disabled external booting so I had to use the slow Internet Recovery (Shift-Option-Command-R) which AFAIR first asked me to activate the Mac. I erased the SSD device and then proceeded to the presented Monterey install (during the install the TV went without signal for about 10 min and I cancelled it and started over. This time I was somehow presented with Mojave install which also had 10 min no signal period but then completed in about 25 min). I hurriedly re-enabled external booting.

https://support.apple.com/en-us/HT204904

Now also the Thunderbolt LG Ultrafine 4K worked fine. Whew!

I booted to the Carbon Copy Cloner external SSD Big Sur backup (I routinely maintain two such bootable backups making sure they boot also after CCC data-only backups), and "legacy bootable" cloned it to the internal SSD. Now everything again works OK.

I do not know why such a simple SMC & PRAM reset might provoke this. A few days earlier Big Sur 11.6.1 had updated the firmware (System Firmware Version: 1715.40.15.0.0 (iBridge: 19.16.10548.0.0,0)) and Monterey 12.0.1 was happy with that firmware and it is still the same version after Revive and Restore.

I'll let the dust settle and try Monterey later making sure to have good backups and another Mac capable to do Revive or Restore nearby.

Posted on Nov 3, 2021 1:37 AM

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Answer 1

Nov 5, 2021 4:41 AM in response to Matti Haveri

I wonder if you could have restored the internal drive by cloning with the Monterey external drive that you knew was working instead? Also, does your other monitor work now on Big Sur with Thunderbolt LG Ultrafine 4K? Just curious what tanked Monterey?

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Answer 2

Matti Haveri Author

Level 6

14,634 points

Nov 5, 2021 5:34 AM in response to bobcollard

After the Restore (which wipes internal drive) I had only the external Monterey test drive with only my random test data.

So I CCC cloned my main external bootable Big Sur SSD backup back to the internal drive which now is back to normal with the Thunderbolt LG Ultrafine 4K (it has only Thunderbolt but luckily I have a LG TV with with HDMI so I could use it for the troubleshooting just when I was getting ready to travel to an Apple dealer).

In fact, I was just about to clone the seemingly OK Monterey install with all my data to the main external SSD CCC backup when suddenly Monterey started to boot only to a black screen (when as a last Monterey install step I routinely reset SMC & PRAM which should fix things instead causing them!). I don't know if using HDMI to a TV would worked at that point and whether it was just a Thunderbolt glitch to the display. I suspected it was a corrupted firmware that has recently plagued also other people and proceeded to Revive and Restore.

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Answer 3

den.thed

Level 9

77,254 points

Nov 5, 2021 10:44 AM in response to Matti Haveri

Big Sur was a real bummer for me and my 2018 Mac Mini. I ended up going back to and staying on Catalina. For me issues with dual displays started back in Mojave on both my 2012 and 2018 Mac Mini’s. The dual display issues settled down for both in Catalina, but the 2018 went nuts again on Big Sur. I took a gamble and upgraded the 2018 Mac Mini from Catalina to Monterey. I must say it has taken to Monterey nicely and it doesn’t look like I’m going to have to go back. Unless they screw-up on the next Monterey update.

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