monitor doesn't work in single monitor configuration, but works fine with any other monitor connected

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Level 1

8 points

monitor doesn't work in single monitor configuration, but works fine with any other monitor connected

I have a monitor (LG 5K) which doesn't work correctly with my mac: it looks like the resolution provided by mac is not recognized by monitor: I can see the picture for a fraction of second and then it turned off, and then again and again. But the strange thing is that it doesn't work only in a single monitor configuration. If I connect another monitor or even connect iPad, monitor works just fine in full 5K resolution. But as soon as iPad or second monitor turned off, the first monitor enter this infinite loop of blinking again.

I've tried to boot in safe mode, nothing helps. I can't change the resolution while I can't see the picture, and as soon as I connect another monitor, everything works and changing resolution doesn't help at all.

I guess there is a configuration stored somewhere in system, which is separate for every monitor configuration. So the one with the only one monitor is bad. How can I reset it without reinstalling the entire OS?

Mac Mini Pro M2, Sonoma 14.5.

Mac mini (M2 Pro, 2023)

Posted on Jun 18, 2024 1:27 PM

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Answer 1

Top-ranking reply

VTolkov Author

Level 1

8 points

Jun 19, 2024 10:39 AM in response to den.thed

LG 34BK95U-W. Connected using thunderbolt cable, which came with the monitor.

But as I said, it works just fine when another display is also connected, so it seems to be a software problem.

I've just tried to switch to usbc-to-DP adapter cable and it works! That solves it somehow. Thank you for the idea.

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Answer 2

BDAqua

Level 10

250,259 points

Jun 19, 2024 6:26 AM in response to VTolkov

To find out if it's system wide or user specific, try this...

Open System Preferences>Users & Groups, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.

Does it work in the new account?

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Answer 3

den.thed

Level 10

92,548 points

Jun 19, 2024 11:02 AM in response to VTolkov

You're welcome.

Yea' there is something off with the LG supplied USB-C cable and/or the timing between the Mac and the display using that cable.

If the USB-C to DisplayPort adapter and LG DisplayPort cable gives you trouble, switch to a short aftermarket high speed USB-C to DisplayPort cable. for example > https://www.amazon.com/dp/B09M38CXZ3/ref=sspa_dk_detail_3?

The other option is to test an expensive Apple Thunderbolt 4 Pro cable.

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