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CLASSIC MUSCLE

macrumors member
Original poster
Jun 16, 2012
47
11
My 16 inch MBP all the sudden stopped waking up the LG 4K display it's connected to. Oddly, it's still getting a charge from the LG monitor, and when I reboot the computer it will suddenly wake up the LG screen and work, but once the MBP goes to sleep again, and then wakes up, the LG monitor won't wake up without a reboot of the MBP. Has anyone else had this issue?
 

AMP12345

macrumors member
Nov 21, 2016
77
94
I had that issue with my Dell p2415q starting on 10.15.2. Switched to public beta and have been having better luck now that I'm on 10.15.4 beta 1, I think it's just GPU drivers that aren't 100% flushed out yet.
 

poorcody

Contributor
Jul 23, 2013
1,121
976
Yes! I've been having this problem for weeks with my 16 inch MBP and the LG 5K Ultrafine. It wakes up randomly but usually does not. Once in a while it doesn't even from a cold boot. The only reliable way to get it to wake it to yank the cord. USB devices plugged into the back seem unaffected.

It worked fine for the first month or so I had the new laptop (and never had it with the 2016 MBP). Seems to be some sort of driver issue.

How old is your 4K? I've been reading in this thread some people think it only affects early versions of the Ultrafines:
https://www.reddit.com/r/MacOS/comments/eqyn5t
 

CLASSIC MUSCLE

macrumors member
Original poster
Jun 16, 2012
47
11
How old is your 4K?

My LG 4K is pretty old, I got it a couple years back when they first released these. It's definitely an early version. Oddly though, mine doesn't even wake up when I pull the USBC cord out and in, it will only bring the screen up with a reboot. Very strange all around here.
 

CLASSIC MUSCLE

macrumors member
Original poster
Jun 16, 2012
47
11
I updated the LG 4K software via LG Screen Manager and this situation seems to have improved, at least for now.
 

poorcody

Contributor
Jul 23, 2013
1,121
976
My Ultrafine is also one of the first models that came out. My firmware is up to date. Problem persists.
 

Appledoesnotlisten

macrumors 6502a
Dec 2, 2017
505
206
My LG 4K is pretty old, I got it a couple years back when they first released these. It's definitely an early version. Oddly though, mine doesn't even wake up when I pull the USBC cord out and in, it will only bring the screen up with a reboot. Very strange all around here.
Hey man, may I ask you a question?
I have a 4K 24" Dell and am thinking about switching to a 22" Ultrafine becsause 24" is too much for my eyes to travel.
What iteration of the 22" Ultrafine would you suggest?
Thank you!
 

pshifrin

macrumors 6502a
Mar 14, 2010
500
378
Hey man, may I ask you a question?
I have a 4K 24" Dell and am thinking about switching to a 22" Ultrafine becsause 24" is too much for my eyes to travel.
What iteration of the 22" Ultrafine would you suggest?
Thank you!
I have had both, first 21.5 ultra fine and then 24 ultra fine. The 21.5 was handed down to someone else in the office.

Keep in mind the 21.5 is USB-C only and supplies only 60w of power and the usb-c ports on the rear of the monitor will only work at usb 2.0 speeds.

The 24 is thunderbolt 3 with 85w of power and the ports on the back are full speed and also have one additional TB port.

The DPI is “lower” on the 24 but not too noticeable to me at normal desk distance.

The 24 works perfectly with my 2019 15 inch. None of the wacky problems you see with the 16 inch.
 
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iMi

Suspended
Sep 13, 2014
1,624
3,199
Same issue on the MBP16 with the screen not waking up. If I open the laptop, the screen just flashes on and off and only disconnecting it from the display returns it back to normal. Then I have to restart the computer for the monitor to work again.

What could be the problem?
 

poorcody

Contributor
Jul 23, 2013
1,121
976
Anyone try 10.14.5 yet? Reports are it fixed the brightness bug -- hoping it will fix the wake-up one too...
 
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iMi

Suspended
Sep 13, 2014
1,624
3,199
Anyone try 10.14.5 yet? Reports are it fixed the brightness bug -- hoping it will fix the wake-up one too...

I am cautiously optimistic. The random issue where waking from sleep would fail has not repeated since yesterday's update. It seems like every morning I have to restart the machine, but not today. I'll report back after a few more days.
 
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iMi

Suspended
Sep 13, 2014
1,624
3,199
Ok, so today is Friday and the issue seems to have been fully addressed. But... now the screen will blink once in a while for no apparent reasons. It's literally a split second refresh. No idea if this is a new bug or something completely unrelated.

Either way -- I have yet to have a wake-from-sleep issue!
 

poorcody

Contributor
Jul 23, 2013
1,121
976
After a couple of days of usage, I can also say the sleep-from-wake bug seems resolved for me too. That was a real pain, glad to see it fixed.

The brightness persistence problem also seems to be fixed. That only took four years!
 

swang14

macrumors newbie
Apr 5, 2020
2
0
I have 3 UltraFine 4K connected to my new MacBook Pro 16-inch. Those three UF 4K I got was purchased from Amazon as renewed, so they are pretty old model I believed.

It was working fine on my old mbp (the 2017 15-inch model), after I switched the new 16-inch model, it stopped wake up from sleep from time to time, and usually two out three wake up fine and the one does not wake up usually can be fixed by replug-in the usb-c cable. however if it does not work by replug, it will be a very serious problem, makes you crazy because the whole OS will crash 100% time, the screen turn to mosaic and it halt, nothing is responding. after 1 minute or two, it will automatically restart or you have manually press the power button to force it restart, you will lost all unsaved work, it's very annoying...

I can understand if there is a bug on GPU driver or whatsoever cause it problem at wake up but hopefully it should not crash my macOS in anyway so I can keep trying or manually restart the OS after save my work.
 

33scottie33

macrumors regular
Aug 24, 2006
114
5
New York
The issue in my case was the Thunderbolt cable that comes with the LG.

Yesterday, I purchased the 27" 5K Ultrafine monitor for my M1 MacMini directly from Apple and was very apprehensive before I plugged it in. Especially after reading about all the issues with it. Everything worked fine. However, this morning, the monitor would not display anything. I tried unplugging the power cable and the Thunderbolt cable and still nothing.

I then plugged it into my MacBook Pro and still nothing. In the heat of anger, I was getting ready to box it up and send it back, but thought, 'Hey, let me try a different cable'. I had an Apple Thunderbolt 3 Pro cable that I used with my old BenQ monitor. And, voila! It worked again. I had planned on selling the Pro cable to offset the cost of the LG, but now I have to keep it!

I plan to order a second LG next week and I'll see if I have the same issue. I'll even try the Thunderbolt cable from the new one on this one. So, I really feel that some of the issues with these LG Ultrafine monitors is a faulty cable. If I didn't have a Pro cable to use, I would have sent it back.
 

jasonCbraatz

macrumors newbie
Oct 27, 2016
1
1
san francisco, california
My 16 inch MBP all the sudden stopped waking up the LG 4K display it's connected to. Oddly, it's still getting a charge from the LG monitor, and when I reboot the computer it will suddenly wake up the LG screen and work, but once the MBP goes to sleep again, and then wakes up, the LG monitor won't wake up without a reboot of the MBP. Has anyone else had this issue?

The problem: The 5K LG Monitor Ultrafine that Apple sold intermittently while they were creating their own doesn't "auto wake up" or stays dead. The MBP sees it enough to produce sound through it, and use the camera, but the monitor never wakes up.

The research: I see hundreds of threads out there with this issue (including https://www.reddit.com/r/MacOS/comments/eqyn5t ) but after hours of reading each one, there never was a fix. Some had success with a reboot or an unplugging of the monitor, but most did not.

The fix: You literally have to use the EXACT same cable that LG sent with the monitor (and) plug it in on the left / rear USB-C port . Watch an old unboxing video (
) for example on the monitor, and you can see that the cable has a special little power stripe on it. In fact, the best success is obtained by following the unboxing video to a "T" since the monitor is so finicky that it likes to have the MBP in an open clam before connecting it if it's been off for awhile.

Why: A real thunderbolt USB-C cable doesn't appear to be enough ; I'm guessing that the frequency must be perfectly achievable or the monitor doesn't think it's connected. This is likely needing a 5A 100W cable Gen2, but I didn't even have success with this one : ( https://www.amazon.com/USB-C-Cable-...&qid=1615671733&sprefix=5k+LG+,aps,187&sr=8-6 ).

I'm going to search to find out more, but this question was asked so many times in the Apple community and I thought perhaps others may benefit from my hours of swearing ( er, troubleshooting ).

jasonCbraatz
 
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