Sometimes my main display doesn't wake up but Mac is still running

[MR_Boogy]

I have a 2012 Unibody MacMini running Mojave. My primary display is a DELL U2715H connected by mini-DP.

For ages I have this intermittent issue where the Mac seemed to be running but the screen wouldn't wake up when I come back in the morning. I end up having to force-power-cycle the Mac.

Today I finally got a 2nd monitor and when my display wouldn't wake up, I plugged it in via HDMI and it worked... so the Mac was running. In fact from testing with 2 monitors, the Mac thinks the main monitor is connected... I can modify its settings and so on, it's just not displaying anything. If I unplug it, the 2nd monitor becomes the main monitor as normal.

So... any ideas what I can do? It seems like the DP is literally not waking up to display to the monitor.
In fact, earlier I managed to click a video window I'd left open on the main monitor when it wasn't working, and it started playing! So the Mac seems to think it is displaying stuff. The monitor knows it is connected.

This single issue is meaning I might have to replace my Mac and I really don't want to as it works great despite its age.

 

[Fishrrman]

I ALWAYS recommend that a Mac be shut down at night and rebooted the next morning. Had to get that out of the way first.

Have you upgraded the OS lately?
Or did this just start happening "out of the blue"?

What connection port are you using on the Dell?
Displayport?
HDMI?
DVI?
Try a different cable. That is, if you're using displayport (on the Dell end), try a minidisplayport (Mini) to HDMI (Dell). Or perhaps MD to DVI (Dell).

If the Dell won't wake up, have you tried:
- Momentarily disconnecting/REconnection the cable?
- Momentarily pressing the Mini's "power on" button? (quick push & release)
- Power down/power up the Dell?

 

[gusping]

I ALWAYS recommend that a Mac be shut down at night and rebooted the next morning. Had to get that out of the way first.

Why do you say this? Almost everyone I know who owns a computer (let alone a Mac), does not turn it off at every single occasion. For all three Macs I have owned, I turned them off once a month at most.

 

[wardie]

Why do you say this? Almost everyone I know who owns a computer (let alone a Mac), does not turn it off at every single occasion. For all three Macs I have owned, I turned them off once a month at most.

A ton of people, including me, use Mac Mini as servers on 24x7 no issues. I’m on my second one, a 2018. I’ve had one or two monitor wake up glitches but nothing serious or permanent. I mostly use it headless though.

 

[MR_Boogy]

I ALWAYS recommend that a Mac be shut down at night and rebooted the next morning. Had to get that out of the way first.

Have you upgraded the OS lately?
Or did this just start happening "out of the blue"?

What connection port are you using on the Dell?
Displayport?
HDMI?
DVI?
Try a different cable. That is, if you're using displayport (on the Dell end), try a minidisplayport (Mini) to HDMI (Dell). Or perhaps MD to DVI (Dell).

If the Dell won't wake up, have you tried:
- Momentarily disconnecting/REconnection the cable?
- Momentarily pressing the Mini's "power on" button? (quick push & release)
- Power down/power up the Dell?

This has been going on for quite a while, across at least 2 major MacOS versions if not 3. It's not the cable, and this is using DP (only way to get QHD support on this version of MM I think).

I've tried pulling display cables and turning the monitor on/off without success though I haven't tested pulling the power cable on the monitor.
A quick push on the Mac power button doesn't do anything.
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I found this which seems relevant, it is suggested Catalina may include a fix but I have apps which aren't supported so am resisting until I decide what to do about that: https://apple.stackexchange.com/que...creen-on-lg-5k-external-monitor/381912#381912