mac mini (2018) displays not waking properly after boot or sleep

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mac mini (2018) displays not waking properly after boot or sleep

Mac mini (2018) has always had strange ways of displaying on the monitors when booting or waking from sleep: the monitors always flickered on and off a few times, but showed ok in the end. This was with each monitor connected to a USB-C port.

As I needed a USB-C port that the (main) monitor was using, I switched to using a HDMI cable for the main monitor, and free up one USB-C. Well, since then either both monitors stay dark after boot, or just one shows, the external one connected via USB-C, as the main screen, with menu bar and dock.

Only after switching off and on the main (dark) monitor the machine detects both monitors, and the situation is corrected. Any idea how to fix this?

Config: mac mini 2018, macOS 12.5, DELL U2715H as main (HDMI), DELL U2713HM ext (USB-C -> Displayport),

Both "Default for display" resolution. "Displays have separate spaces" is OFF.

Posted on Jul 29, 2022 10:39 AM

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Answer 1

Jul 31, 2022 9:02 AM in response to Rick Jansen1

Hi Rick Jansen1,

Thank you for participating in the Apple Support Communities. This article has a few steps that may help:

If your external display isn't detected or appears blurry when connected to your Mac

Things like updating macOS and testing another HDMI cable may help. You may also want to check to see if your monitors have any firmware updates available.

Also, try resetting the SMC using the steps here: How to reset the SMC of your Mac - Apple Support This may help with the behavior of power related items such as displays.

Take care.

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Answer 2

den.thed

Level 10

96,816 points

Aug 1, 2022 7:03 AM in response to Rick Jansen1

What else do you have or want to plug into the USB-C ports?

Then 2018 has 4 USB-C port, I would go back to one Dell display on Bus 0 and one Dell display on Bus 1.

Then I would get and use a USB-C hub, if I needed more than the 2 remaining USB-C ports.

If I was forced into using one of those Dell displays on the HDMI port instead of USB-C to DisplayPort.

Then I would test it on a short Premium Certified HDMI cable, instead of the cheap-o Dell supplied cable.

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Answer 3

den.thed

Level 10

96,816 points

Aug 1, 2022 7:48 AM in response to Rick Jansen1

I would go back to what "It had" and add a USB-C hub and connect two of the external drive to it.

Or optionally move the slower external HDD to the Mac mini's other USB-A port.

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Answer 4

den.thed

Level 10

96,816 points

Aug 1, 2022 8:30 AM in response to Rick Jansen1

Yeah' macOS has had some sleep/wake/startup issues with dual displays for some time now.

Apple does not monitor this User to User forum and as another user, I can only suggest sending feedback.

Feedback - Mac mini - Apple

Feedback - macOS - Apple

FWIW

I use the following Energy Saver setting on my 2018 Mac mini with dual displays.

I have all the Spaces boxes in Mission Control unchecked.

I have the Screen Save disabled and only restart for updates.

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Answer 5

hcsitas

Level 6

13,970 points

Aug 26, 2022 4:35 AM in response to Rick Jansen1

Snapshot of your Energy Saver Preferences please?

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Answer 6

den.thed

Level 10

96,816 points

Aug 26, 2022 5:17 AM in response to Rick Jansen1

The Monterey 12.5.1 update was a small step backwards for my 2018 Mac mini with dual displays as well.

Problem is that these updates are most likely focused more on the M1 models.

Again my advice is to send feedback to Apple using the feedback links that I provided above.

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Answer 7

den.thed

Level 10

96,816 points

Aug 26, 2022 8:24 AM in response to Rick Jansen1

You’re welcome.

Yea’ two steps forward, one step back.

I have no idea what, but something changed in 12.5.1 that was finally working fine in 12.5. I say that, because I had to go back to occasionally using a Hot Corner set to Sleep Displays, to get the reluctant display to light up.

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Answer 8

Rick Jansen1 Author

Level 1

15 points

Aug 30, 2022 6:24 AM in response to Rick Jansen1

I have no idea what has changed, but currently sleep works, and so does the hot corner.

Here is an interesting web page: https://michaelkummer.com/tech/mac-sleep-fix/

It shows how the Activity Monitor can display an extra column "Preventing Sleep", labelling processes that prevent sleep. I should have found this earlier.

Basically: Activity Monitor -> View menu -> Columns> -> Preventing Sleep (check this)

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Answer 9

Rick Jansen1 Author

Level 1

15 points

Aug 1, 2022 12:02 AM in response to Matthew.S81

Thank you for your reply. I had done the NVRAM and SMC/T2 reset, I now have run out of Vulcan death grips I think.

macOS is uptodate, another HDMI cable does not help.

Only after switching off/on the external monitor (USB-C) mac notices it has monitors connected, and both the HDMI and the USB-C connected one work. At that point mac has booted with two dark screens.

It all does work ok if both monitors are connected to USB-C/thunderbolt, there is an image of the boot process.

USB-C connected monitors are noticed by mac, and vice versa, the USB-C connected one briefly shows it's Energy Logo when mac is booted. However, the HDMI connected one is not noticed, and it does not see that mac is "on". Only after power cycling the USB-C monitor video starts up. That makes me think the cable basically is okay, but there is miscommunication on the mac side, as it fails to see the HDMI connected monitor.

Aha: when only one monitor (HDMI) is connected boot works fine. When the USB-C display is added I get two dark screens during boot. Apparently it's the combination that makes things fail.

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Answer 10

Rick Jansen1 Author

Level 1

15 points

Aug 1, 2022 7:36 AM in response to den.thed

It had:

HDMI: unused

USB-C 1: external SSD

USB-C 2: Dell monitor main

USB-C 3: Dell monitor external

USB-C 4: external HDD

It now has:

HDMI: main monitor

USB-C 1: external SSD

USB-C 2: Dell monitor external

USB-C 3: external HDD

USB-C 4: external SSD

I have tried different HDMI cables, and if I only use the main monitor on HDMI and disconnect USB-C 2 it works fine, except that I then don't have the external monitor. I must assume the cable is ok?

USB2 has the USB cable of the main monitor, for keyboard, mouse, external speakers, ipad,iphone etc. I use the monitor as a USB hub.

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Answer 11

Rick Jansen1 Author

Level 1

15 points

Aug 1, 2022 8:03 AM in response to den.thed

Thanks for the reply, I understand what you mean, but that spare USB-A port is when I need iPad connected and charging.

I now think it's a bug Apple needs to fix, and filed a *cough*Bugreport*cough* Feedback issue.

I can live with it for now, wake on sleep works, though it wakes up the external monitor first, and the login screen appears there. After login the main screen wakes up too, although I have had windows moved to the wrong display.

The main problem now is with booting, which I don't do that often.

(Not that you don't need to fix this, @Apple! *frowning*, you are not some cheapo maker, are you?)

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Answer 12

Rick Jansen1 Author

Level 1

15 points

Aug 1, 2022 10:04 AM in response to den.thed

Thanks again for that, copied your settings where applicable: no change: dark boot.

How are your monitors connected? Both thunderbolt/USB-C? No HDMI?

Anyone else have a working setup with one monitor on HDMI and the other on thunderbolt/USB-C?

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Answer 13

Rick Jansen1 Author

Level 1

15 points

Aug 26, 2022 2:03 AM in response to Rick Jansen1

Since macOS 12.5.1 something has changed: sleep does not work any more. Mac wakes a few seconds later, with the login screen. In the past you could click "Cancel" and mac would sleep anyway, but not any more. After "cancel" it wakes up again after a few seconds. So now I switch off my monitors with their power buttons.

Come on Apple, this is clumsy, at least.

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Answer 14

den.thed

Level 10

96,816 points

Aug 30, 2022 7:09 AM in response to Rick Jansen1

Glad to hear sleep and hot corners are working again.

Also glad to see that you found "Preventing Sleep" feature in Activity Monitor. Keep in mind that most of those Yes's, will only affect Auto Sleep and that selecting Sleep from the Apple dropdown you may over ride them.

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Answer 15

Rick Jansen1 Author

Level 1

15 points

Aug 26, 2022 4:50 AM in response to hcsitas

All checkboxes off:

Behaviour is the same with the default settings (wake for network, enable power nap).

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mac mini (2018) displays not waking properly after boot or sleep

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