Triple displays on Mac Mini lose signal when screen is locked

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Level 1

34 points

Triple displays on Mac Mini lose signal when screen is locked

I have a Mac Mini 2018 (i3) with the Sonoma 14.6.1 installed.

I use external monitors (not Apple). I have three monitors of different models. The problem occurs on all of them. I can't list them all now, but if needed, I can add this information later. At the moment, I am using ViewSonic VX2239wm. I am using HDMI connection.

The other two monitors are connected simultaneously. One via HDMI, and the other via HDMI / thunderbolt adapter.

The problem is as follows: If I need to leave the computer and I lock the active session (Control + Command + Q), then after 5-10 seconds the image on the monitor disappears completely. A message appears about the lack of signal. Sometimes it is necessary to disconnect the monitor for the image to appear again. Since the problem occurs on different monitors of different brands, I assume that the problem lies somewhere in the computer itself.

In a dual-monitor configuration, after unlocking the screen (or waking up from sleep mode), sometimes one of the monitors does not turn on. It also has to be disconnected for the computer to see it.

So I guess the computer at some point stops sending a signal for a period of time, after which the monitor does not see the computer, or something else. Maybe someone has encountered this and was able to solve the problem?

My monitor settings on screenshoot

[Re-Titled by Moderator]

Mac mini, macOS 14.6

Posted on Sep 3, 2024 4:11 AM

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Answer 1

Top-ranking reply

hcsitas

Level 6

12,686 points

Sep 10, 2024 7:02 AM in response to Blackful

Could you post a sketch of the 3 monitors and their connections/connection types? Add make & model number too, thanks.

Be sure you’re sticking strictly to spec. If you’re deviating from spec or stretching it something that’s not clearly not stated, you have no choice but to live with side effects, unfortunately.

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Answer 2

lanstrad1

Level 2

414 points

Sep 9, 2024 8:54 AM in response to Blackful

I have used 3 monitors succesfully on my mini 2018 years ago (not Sonoma then…). If i recall correctly, one (viewsonic indeed) on hdmi port, the two others on an expensive hub (with 2 hdmi ports) through a usb-c/tb port. No issues back then. Can’t tell now as i use two (one on hdmi and for other purposes, still that hub for the orher one.

i see there are some extended display splitters for about $80 now, can’t tell about the reliability. Mine (back in 2020) was over $250….

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Answer 3

hcsitas

Level 6

12,686 points

Sep 11, 2024 1:52 AM in response to Blackful

(2) is good but (1) needs an adapter that’s Apple-certified i.e. this one About the Apple USB-C Digital AV Multiport Adapter - Apple Support.

Return if it doesn’t do the job. And please stick to this configuration until the discussion either hits a deadend or works, thanks.

Additionally, be sure to not use an HDMI cable longer than 3’/1m. Must be either that or shorter.

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Answer 4

hcsitas

Level 6

12,686 points

Sep 10, 2024 5:12 AM in response to Blackful

On 2nd thoughts, I would disable the screen saver and off the display after 10 minutes (or an hour if you prefer). The screen saver is IMO a gimmick that consumes power and wears the display, best avoided.

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Answer 5

Blackful Author

Level 1

34 points

Sep 11, 2024 1:02 AM in response to hcsitas

:D

Dual-monitor conf is next:

AOC C24G1 (model 24G1), connected with same HDMI/Type-C adapter.
Philips 272B8QJEB/00 (model 272B8Q), connected with HDMI/HDMI

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Answer 6

Blackful Author

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34 points

Sep 10, 2024 4:26 AM in response to hcsitas

This is how it look now

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Answer 7

Blackful Author

Level 1

34 points

Sep 10, 2024 4:57 AM in response to hcsitas

You mean this?

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Answer 8

hcsitas

Level 6

12,686 points

Sep 10, 2024 5:32 AM in response to Blackful

In that case, disable the display off-after-timer permanently. As for the screen saver, see if enabling it solo fixes the problem?

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Answer 9

hcsitas

Level 6

12,686 points

Sep 10, 2024 8:06 AM in response to Blackful

That monitor is older than prehistoric ancient running Ford Pinto HDMI 1.0. Replace with new without a second thought.

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Answer 10

Blackful Author

Level 1

34 points

Sep 11, 2024 2:04 AM in response to hcsitas

Ok thank you for you help!

I will try find this one here in closest future.

Yes, I use cables 1 and 1.5 m

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Answer 11

Blackful Author

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34 points

Sep 10, 2024 1:43 AM in response to lanstrad1

The only difference now (with ViewSonic) between connecting HDMI and an HDMI-to-lightning adapter is that if HDMI is used, you need to turn off the power to the monitor after the signal is disconnected to restore operation. With the adapter, the monitor wakes up itself if you press a key. Most often. But the problem is not this, but that the monitor turns off in principle. Any of the monitors:(

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Answer 12

Blackful Author

Level 1

34 points

Sep 10, 2024 5:25 AM in response to hcsitas

The problem here is a little different. My job does not allow me to leave the computer unlocked. So every time I leave, I lock it (Control + Command + Q). And the monitors go into sleep mode after 20 seconds. And this is a problem when I return within 5-10 minutes, because it is often quite difficult to "wake up" these monitors. That is why I would like the screensaver to work instead of turning off the monitor. The monitor works about the same as a working day anyway. When I finish work, the monitor always turns off.

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Answer 13

Blackful Author

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34 points

Sep 10, 2024 5:59 AM in response to hcsitas

Thanks to all these attempts, I found another pattern.

Screen off is disabled.

Screensaver is turned on automatically after 1 minute (1 minute for testing, so as not to wait too long).

If the screensaver turns on automatically after 1 minute of non-use of the computer, then the screensaver works properly and the monitor does not turn off (it definitely did not turn off for 5 minutes). At the same time, I do not see the time, date and password entry field on this screensaver.

If I forcibly lock the computer (Control + Command + Q) or lock it through the system menu (Apple logo --> Lock Screen), then the problem with turning off the monitor that I described is observed. At the same time, before the monitor turns off, I see the time, date, password entry field.

Based on this, I see the problem exclusively in the use of forced blocking.

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Answer 14

Blackful Author

Level 1

34 points

Sep 10, 2024 7:54 AM in response to hcsitas

I don't use 3 monitors at same time. Only 1 or 2. But yes. I can do it of course.

Now I can tell about only 1 monitor conf. About 2-monitor conf I can tell later today.

So for now it ViewSonic VX2239wm (Model VS13513). Installed to 1080p, 60 Hz.

Connected HDMI to HDMI. It can be used noname HDMI/Type-C adapter from local store.

You might think that the problem is in the adapter. But on other devices with type-c support everything works absolutely correctly. And then there would be no problem connecting directly via HDMI.

I'll try to find other Mac devices and test it too. I'll be able to give information about the dual-monitor configuration a bit later.

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Answer 15

hcsitas

Level 6

12,686 points

Sep 4, 2024 11:55 AM in response to Blackful

Use these settings exactly as shown, might fix:

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