2018 Mac Mini - monitor problems

I just got my first Mac Mini/Mac Desktop and i'm having the same issues with 4K monitors. After messing with settings and finding out that something is keeping the video card from running, so i decided to turn off FileValut. Reason why did that because it seemed weird the monitors wouldn't come on, but when i first set it up the MacMini and rebooted a few times it worked perfectly. The only thing i did after setting it up was enabled FileVault. So i powered on my Mac and waited a 30 seconds then clicked my mouse and type in my password like i always do on my MBP. That worked and i was able to see it fire up and my displays worked.

So disabling FileFault is what I did but its for sure not the most ideal fix. I would love to have my hard drive encrypted, but it resolved it for me for now. Guess i'll have to use another way to encrypt the hard drive to see if that breaks it as well. Thought i would share that with anyone that is wanting to test it out.

"The short cable that came with the BlackMagic eGPU made the biggest difference for me. The cord I had been trying worked just fine for everything else - but not with the eGPU."

The eGPU uses Thunderbolt 3. Short cables can work for both USB and Thunderbolt 3.

https://www.apple.com/shop/product/MQ4H2AM/A/thunderbolt-3-usb%E2%80%91c-cable-08-m

For greater distances with Thunderbolt 3 you need special Thunderbolt 3 cables with the lightning bolt icon on the USB-C plugs.

Belkin Thunderbolt 3 5A Cable (2 m) - Apple

Just to let you know, unplugging your mini resets the SMC, not the PRAM. The PRAM is reset by holding down the cmd and option keys along with P and R during start up. This explains the PRAM reset https://support.apple.com/en-us/HT204063 and this explains the SMC reset https://support.apple.com/en-us/HT201295

I want to purchase the mini instead of the new iMac since the mini has up to 10Gb Ethernet which will make it future proof. The new iMac still has only has 1Gb Ethernet. I'm guessing that in about 3-5 years we'll have at least 5Gb available to the desktop.

I know that most folks here are having monitor issues. I'll ask again, but with the recent OS update, if I connect one LG UD monitor from the mini using USB C to DisplayPort, will this work properly now? Also, someone mentioned the periodic switching of audio from USB to internal speaker for five seconds. That would be a deal-breaker for me. Are others experiencing this also?

The same issue I had (Dual monitors on mac mini 2018 do not turn ON reliable).

For me : both LG monitors on TB3 was no fun : with one on HDMI and one on TB3 is better AND still it fails on reboot (sleep seems to work). I've tried everything and it simply does not work reliable.

Thanks so much Rayluca2! Yes the 10.14.6 beta has cured the issues for me as well.

I was able to re-enable Deep Sleep mode on my monitor. I can startup, restart, sleep, wake from sleep, and enter recovery mode with no issues regardless if I'm using HDMI to HDMI or USB-C to DisplayPort. This is all at 60Hz which is as advertised. If I try to run above 60Hz things get dicey again, but this is fine.

I'm sorry drifter7508 you are not having the same luck. You might want to try clearing the PRAM and SMC after installing the latest beta of 10.14.6 if you haven't already.

https://support.apple.com/en-us/HT204063

https://support.apple.com/en-us/HT201295

I've had these same issues where my display goes black on boot, lockscreen, or sleep and tried other solutions as noted on this thread, such as swapping out cables, using different ports, not turning off Mac Mini, etc. My problem with the display going black (no signal) was so SEVERE that I was seriously going to buy a new monitor or return my Mac Mini and get a Macbook laptop instead. Trying a new monitor was not an option for me, I don't have the funds right now to go buy a new gaming monitor. Especially after my new Mac Mini purchase in May 2019 and new monitor Samsung C32HG70. Any extra old monitors that I had laying around my house were given to friends last year so I didn't have available test bench equipment.

Hardware I'm using:

Samsung C32HG70 32-inch HDR QLED Quantum Dot Curved Gaming Monitor (144Hz / 1ms) Model C32HG70QQN

https://www.amazon.com/dp/B06XT6WQCJ/?coliid=I1VUC0FZY8WHCW&colid=FJKVUTS6GSEI&psc=1&ref_=lv_ov_lig_dp_it

This is a newer monitor model that I purchased from Amazon and had great reviews. I use my Mac Mini mostly for YouTube and gaming using Parsec (where I remote access my Windows 10 gaming rig in my house).

My Mac Mini 2018 hardware:

Hardware Overview:

Model Name: Mac mini

Model Identifier: Macmini8,1

Processor Name: Intel Core i7

Processor Speed: 3.2 GHz

Number of Processors: 1

Total Number of Cores: 6

L2 Cache (per Core): 256 KB

L3 Cache: 12 MB

Hyper-Threading Technology: Enabled

Memory: 32 GB

Boot ROM Version: 996.0.0.0.0 (iBridge: 17.16.10482.5.10,0)

Activation Lock Status: Enabled

Another forum member suggested to download the new MacOS, and I would like to give a huge THANK YOU to whoever that was. The only solution that is worked for me so far is to enroll in the beta program and download the new Catalina (beta) MacOS. In my opinion this is either a driver problem or firmware update that Apple did with the new MacOS. I downloaded Catalina (beta) 3 days ago and tried to replicate my screen issue and the good news is I have not been able to break anything.

When I power on my 2018 Mac Mini with new Catalina OS, there seems to be a new screen refresh with Catalina right before you see your login prompt.

This screen refresh, whatever is doing behind the scenes, seems to have corrected this issue. Even though 3 days with my new OS is a small sample size, I've done a lot of testing and no new instances of no signal black display issues with my monitor have occurred.

I recommend that for anyone having display issues where monitor goes black (no signal) with their 2018 Mac Mini to upgrade immediately to beta Catalina MacOS. This is a free upgrade, you only have to enroll in the Beta program with Apple. Just make sure that you backup any important data that you have before you upgrade just in case things go south. I have another computer that hosts my critical data, so I upgraded without much hesitation.

My current OS version:

10.15 Beta

Link for beta program:

https://beta.apple.com/sp/betaprogram/redemption#macos

This is hidden away in the MacOS Catalina 10.15 User Guide under the Use Multiple Displays topic at https://support.apple.com/guide/mac-help/use-multiple-displays-mchl7c7ebe08/mac

Note that it states that you may have to press the Option key to make the Detect Displays button appear. Interesting that this wasn’t mentioned in so many phone calls with Apple support techs. I guess it’s just as thoroughly hidden away in their knowledge base.

Apple support sent me a USB-C Multiport adapter to see if this would be a workaround and the monitor came up right away. Unfortunately, it only supports 30hz on the Mac Mini 2018. Don't know why the mini would be different but it is... https://support.apple.com/en-us/HT207806.

I also tried just leaving the adapter in with no HDMI connection to it and used a USB-C to displayPort adapter and the monitor came up fine again but pushed the refresh rate down to 30hz. No good, but maybe a single USB-C to HDMI port that supports 60hz might work or the issue could be all about the refresh rate.

I was searching for any other answers I could find for this issue (I've had problems again following a reboot) and there's some compelling info at gpu.io:

https://egpu.io/forums/mac-setup/mac-mini-egpu-not-able-to-connect-direct-to-monitor/

https://egpu.io/forums/mac-setup/mac-mini-2018-no-display-after-a-reboot-or-coming-from-a-shutdown/

The recommendation is to reinstall macOS with your display connected directly to your Mac, and never install system updates with the display connected via the eGPU. The relevant bit of text comes from Apple's page on the Blackmagic eGPU:

Learn more

macOS currently doesn't support eGPUs in Windows using Boot Camp or when your Mac is in macOS Recovery, at FileVault login, or installing system updates.

I haven't tried a reinstallation yet but if and when I do, I'll report back.

If you want to wipe the drive and do a clean OS install from a thumb drive, you need to set your machine to allow external boot.

You can Google how to make a bootable usb installer. Here’s the step to allow booting from an external drive.

https://support.apple.com/en-us/HT208330

I bought a new monitor (Dell U3818DW) and it arrives before sending the Mac-mini the repair center. I've made some tests.

1. Connected only the Dell display to the Mac Mini using the USB-C ports, reboot, cold restart, sleep and wake up, no problems.
2. Connected Dell display and Cinema Display, on 2 USB-C ports, reboot, cold restart, sleep and wake up, no problems.
3. Connected Cinema Display on USB-C (after the other tests), reboot, cold restart, sleep and wake up, no problems.

So far, there is no more problems on the Mac Mini not starting, reboot, kernel panic, freezing and so on. For those who are having problems to get an external monitor working with Mac Mini, try to connect other Monitor on the USB-C port, connect your monitor to the USB-C and then connect just your monitor. Can be related to the configuration that the Mac Mini stores from the monitor.

Using an AOC 32" 4k monitor (which works swimmingly with my 2015 MBP) with formerly fabulous 2018 Mac Mini:

• Purchased on November, worked fine until a month or so ago. Connecting TB3 to HDMI.
• Beginning a month or so ago I had an issue starting up wherein it would take me directly to Reset Password, which my wireless mouse was useless for and wired keyboard couldn't get me out of. Physically turning off, then doing a PRAM reset seemed to get me around this.
• "No Signal" to monitor began shortly thereafter - for whatever reason switching to a different TB3 port worked.
• "No Signal" to monitor began happening upon every restart. Switching TB3 output stopped working. PRAM reset stopped working.
• Purchased Sonnet Puck EGPU (directly from Apple.com, so, like, compatibility assumed) yesterday thinking this would fix the issues, along with making Adobe graphics (I gots prototypes to make!) programs less choppy.
• Currently: After attempting various methods of connection (only thing I haven't tried is HDMI to HDMI, but if that's the only thing that works my $400 egpu is useless) the best I can get is an Apple icon with load bar for about 10 seconds before signal is lost again.
• Have not tried disabling FileVault because I need to actually see a UI for that.

Hey, Apple, you know the Mini depends on an external monitor for basic functionality/usability, right? That's, like, the very base of the user experience pyramid - being able to use the ******* thing.

There does not seem to be an Apple fix, so I am using this work-around:

Think server + dumb terminal. When I worked in IT the server was on 24/7 and dumb terminal, etc were connected & lit as needed.

My Mac Mini 2018 is now on 24/7 with no need to wake-y, wake-y.

(1) System Pref --> Energy Saver

• Turn display off after-->Never
• Check prevent sleeping... All other boxes off

(2) System Pref-->General-->Check Require Password & set time (I use 5 min)

If leaving the active computer for a while you can log out or sleep the screen with the mouse pointer and system times out to require log on.

For longer periods, I log out, and turn off the LG monitor. (Déjà vu my main-frame days...)

A clean install of Catalina had left me with a pink-purple start screen after shutting down. An "Out of range" message would appear and the image would look normal after logging in. After the October 15 supplemental update, I'm back to blank. No starting Apple logo and resetting the PRAM is necessary to start from power off. I'm keeping the Mac mini eternally asleep, for the moment.

To those wondering if this is exclusively an LG issue or a 4k issue, it's not. I've had this issue with:

• My current LG 27UK850 4K monitor. It woke up after shut-down with some versions of Mojave, but not with others. Not in Catalina either.
• A Samsung 1080p TV, which has been connected to my STB through HDMI for years. Same with Mojave (it worked with some versions). I haven't tried with Catalina.

Encouraged by @eiskarlsson's experience I installed LG's OnScreen Control software to try to update the monitor's firmware. Mine doesn't seem to have the option, as I can only see a desktop-arranging menu.

I can appreciate the bravery of those going the route of dongles and adapters. I won't go that way, this is a brand new monitor with LG's supplied HDMI cable and a relatively new Mac that has worked before with previous macOS versions. It should work now if the issue was identified.

And receiving the answer that only LG's Ultrafine 4k or 5k monitors are the supported ones because they're featured on the Apple Store is simply unacceptable in my opinion. That's why we have standards like HDMI, otherwise this industry would be chaos.

System: Mac Mini (2018) /Monitor: LG 27UK850-W 27" 4K UHD/cable USB-C <--> USB-C, came with LG monitor.

OpSys: Catalina 10.15 (19A602) with the recent update.

1. SSD sleep, monitor in power-save: press any of shift/control/option/command once: OK, wakes up & can login.
2. Restart--> proper boot up apple image, OK & can login.
3. Big surprise! Cold boot--> proper boot up, apple image, OK & can login.

I have no idea what caused this to behave like a real computer & monitor for a change. I hope it lasts.