Issue with LG 27UP850-W 4K external screen. "No signal" on MBP 16 M1 Pro.

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Level 1

29 points

Issue with LG 27UP850-W 4K external screen. "No signal" on MBP 16 M1 Pro.

Hi,

I bought brand new monitor LG 27UP850-W 4K. When I connected it (for the first time) to working MBP 16 M1 Pro via USB-C cable everything worked fine. MBP started charging, LG monitor was running fine. The problems happen when I restart or turn MBP off. During boot-up LG monitor shows "no signal" info and nothing else happens. MBP is not being charged and LG monitor eventually goes to sleep. If I want to see something again on LG monitor I need to turn it off completely and turn it on again. After that MBP starts to see LG, which starts working again, and MBP battery starts charging.

The same issue, also via USB-C, is not happening on Windows machine (Dell laptop). When laptops starts after being turned off LG monitor starts simultaneously.

I have the current version of Monterey - 12.0.1. Do you maybe know how to solve this issue?

Posted on Nov 23, 2021 12:54 PM

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Answer 1

SzariK Author

Level 1

29 points

Dec 17, 2021 8:56 AM in response to Sonicray

I think it won't help. This is a broader issue: https://discussions.apple.com/thread/252055990

Moreover I bought another LCD screen, ASUS ProArt PA27A with Thunderbolt connection. The same issue.

Is there any one who solved this somehow or another fix from Apple is needed here?

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Answer 2

SzariK Author

Level 1

29 points

Dec 18, 2021 12:59 AM in response to Sonicray

Another bigger thread on the same issue: https://www.reddit.com/r/macmini/comments/ql025a/external_monitor_not_waking_up_issues_solved_with/

Issue is related to USB-C or thunderbolt ports. I have not experienced the same issue on HDMI ports. Moreover, I check and the same issue is happening on MacBook Pro 16" 2019.

I think this is a software related issue as the same monitors works perfectly with Windows machines.

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Answer 3

Sonicray

Level 5

4,555 points

Nov 24, 2021 2:21 AM in response to SzariK

You should contact LG's tech support via their website:

https://www.lg.com/us/support/help-library/monitor-connecting-to-a-mac-CT10000030-20150911473158

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Answer 4

SzariK Author

Level 1

29 points

Dec 18, 2021 7:39 AM in response to Sonicray

Problem solved. I discovered that Asus, by default, enables "Deep energy saving" option. I changed energy saving to "normal" value and now everything works fine on thunderbolt.

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Answer 5

Sonicray

Level 5

4,555 points

Dec 18, 2021 1:19 AM in response to SzariK

By the way Asus has a firmware update for their ProArt monitors. They also recommend using a HDMI cable and to upgrade the USB hub software (so, check Asus’ site)

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Issue with LG 27UP850-W 4K external screen. "No signal" on MBP 16 M1 Pro.

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