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ryne275

macrumors newbie
Original poster
Apr 10, 2018
13
6
Thanks to Mojave 10.14.6, my Mac mini now refuses to properly output to a display (only upon initial boot) when using an HDMI to DVI cable. I have to replug in the cable in order for it fix itself. Very, very inconvenient. I've tried SMC/NVRAM flush, safe boot and NOTHING seems to fix the issue.

How can I "downgrade" to the initial software my 2018 Mac mini came with---Mojave version 10.14.2?
  • I, unfortunately--because I didn't think anything bad would come of it---didn't make a Time Machine backup before updating from 10.14.2 to 10.14.6
  • However, my 2017 Macbook Air is still on Mojave 10.14.1---can I simply create a USB Time Machine backup on my Air and then use that same backup to downgrade my 2018 Mac mini from 10.14.6 to 10.14.1?
 

madrich

macrumors 6502a
Feb 19, 2012
544
91
World Class City of Chicago
I think you should be able to connect your MBA with your mini and copy files from your MBA to the mini, but you would erase the mini in the process. Like wise you should be able to connect your mini to the Time Capsule and join it to backup disk that you want to restore. Again you will erase what was on the mini.
 

weaztek

macrumors 6502
Aug 28, 2009
330
155
Madison
It's weird because 10.4.6 fixed a lot of display problems on the Mini. Particularly a pesky wake from sleep bug I used to have. At the moment i'm running my 32" LG with a USB-C to DisplayPort adapter because Catalina had big problems with the HDMI port.

I wouldn't go back to 10.14.1 so fast. Keep troubleshooting the Mini and the cable because you might just wake up the next day and it will all work.

Have you tried running it a different resolution?
 

MacUser2525

Suspended
Mar 17, 2007
2,097
372
Canada
I wouldn't go back to 10.14.1 so fast. Keep troubleshooting the Mini and the cable because you might just wake up the next day and it will all work.

There is good possibility he cannot revert to that version. Apple limits it machines to the operating system it originally shipped with for a re-install I am not positive if it is so fine grained that it will insist on the 10.14.2 that came with the machine. But it would be best to at least download the combo update for that version and apply it to a clone of the 14.1 before using it to boot the mini for a re-install of it there. Carbon Copy Cloner or SuperDuper will do nicely for this task.
 

Fishrrman

macrumors Core
Feb 20, 2009
22,640
8,517
OP:

It's gonna be hard to get back to earlier version of Mojave.

Having said that, you're not the only one who has the "black screen at boot" problem -- I sense it's common to probably 50% or more of the Minis "out there". Maybe a higher percentage.

I've come to the conclusion that this is "unfixable" by Apple because the core of the problem actually lies with the type of cable being used, the characteristics of the display being used, and the many permutations that might exist between these two factors. Factors that are "beyond Apple's reach", so to speak.

OK... having said all that nonsense...
What can you do to resolve the problem?

First -- What are the "full range of input connections" you have on the back of the display?
Do you have HDMI?
Do you have displayport?

IF the display has an HDMI input, it might be worth ordering a GOOD HDMI cable, and see if that "works around" the problem.
You want an HDMI 2 (the "2" is important) "high-speed" cable.

IF the display has displayport, you might try a "USBc to displayport" cable. Make sure it's a good one, and CHECK THE REVIEWS to see that it works with the Mac.

EVEN SO...
... you're probably STILL going to get the blackout at boot -- BUT, once it blacks out, it should "come right back" after a second or two.

That's how my Mini works with an HDMI (mini) to DVI (display) connection -- always goes black, but always comes back. That'll do for me.
 

Project Alice

macrumors 68000
Jul 13, 2008
1,749
1,708
Post Falls, ID
This sounds more like user error or a bad cable to me.
Computers can be weird with HDMI sometimes; especially if its a TV you’re connecting to. Either way, try a different cable/different adapter.

What reason could you possibly have for not running 10.14.6 by now? 10.14.6 is a world of difference for the better compared to early builds.
I’ve been running 10.14.6 on unsupported models as well as my MP5,1 and have never experienced anything like this.

Whenever I see a thread saying “an update broke my computer” 10/10 times it didn’t. It’s a coincidence.
 

madrich

macrumors 6502a
Feb 19, 2012
544
91
World Class City of Chicago
This sounds more like user error or a bad cable to me.
Computers can be weird with HDMI sometimes; especially if its a TV you’re connecting to. Either way, try a different cable/different adapter.

What reason could you possibly have for not running 10.14.6 by now? 10.14.6 is a world of difference for the better compared to early builds.
I’ve been running 10.14.6 on unsupported models as well as my MP5,1 and have never experienced anything like this.

Whenever I see a thread saying “an update broke my computer” 10/10 times it didn’t. It’s a coincidence.
Read this: https://apple.news/Ac9oLWLHDRw-tAFcanD7Unw
 

Project Alice

macrumors 68000
Jul 13, 2008
1,749
1,708
Post Falls, ID
That is completely unrelated to the topic at hand. It's about Catalina, and an EFI problem. The OP's problem is about a display issue.
Also, that article is entirely speculation. If it does turn out to be true, apple would issue a fix or a statement about it. Not to say that can't happen, it absolutely could; but every year there are always a small amount of people blaming an update for their computer not working.
 

madrich

macrumors 6502a
Feb 19, 2012
544
91
World Class City of Chicago
That is completely unrelated to the topic at hand. It's about Catalina, and an EFI problem. The OP's problem is about a display issue.
Also, that article is entirely speculation. If it does turn out to be true, apple would issue a fix or a statement about it. Not to say that can't happen, it absolutely could; but every year there are always a small amount of people blaming an update for their computer not working.
What I and others are trying to say is that software can corrupt or destroy hardware. My personal experience was with Mavericks upgrade. My early 2008 MBP was working superb without any problems with Snow Leopard OSX. When I upgraded to Mavericks OSX it destroyed my Mother/Logicboard which I had to replace. When Apple replaced the Motherboard I instructed them restore Snow Leopard. I stayed on SL until El Capitan was finalized for my MBP.

For my MBA early 2015, until two weeks ago I have been with the original installed El Capitan OSX and have now upgraded to Mojave without any problems. I only upgraded because to Mojave because my iPhone and iPad were orphaned from my MBA.
 
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