How to find the cause of display flickering and to fix it

morning-tea · 10-06-2020, 11:49 PM

Hi all,

Just purchased a new Dell 4K 31.5" U3219Q display. It flickers now and then occasionally, turning to a black screen and back in about 5 to 15 seconds. It happens sometimes automatically and another time when I click the mouse.

The HDMI cable is having metal shell woven mesh cover and ferrite bead at both ends.

Please advise how to fix the problem?

Thanks

Regards

computersavvy · 10-07-2020, 11:47 AM

I would guess that it is not perfectly synced with the driver. ie. the driver may think it should be at 120hz and the monitor is looking for 126hz or some such.

I don't know what tools or drivers you have but I am using an nvidia card and with nvidia settings I can see that my monitor is synced at 74.97 hz.

Try looking at the monitor & driver settings and make certain they are properly synced. It might be that the card & driver cannot fully meet what the new monitor expects.

smallpond · 10-07-2020, 12:03 PM

You can use xrandr to determine current and supported configurations.

TB0ne · 10-07-2020, 12:36 PM

Quote:

Originally Posted by morning-tea

Hi all,
Just purchased a new Dell 4K 31.5" U3219Q display. It flickers now and then occasionally, turning to a black screen and back in about 5 to 15 seconds. It happens sometimes automatically and another time when I click the mouse.

The HDMI cable is having metal shell woven mesh cover and ferrite bead at both ends.

You don't tell us anything about your computer or what it's running (version/distro of Linux), desktop environment, or graphics card...we can't guess. That said, does it happen on your old monitor?? With a different computer? Anything else plugged into the monitor besides the HDMI cable?

And have you considered that you just got a bad monitor?

morning-tea · 10-07-2020, 11:35 PM

Hi all,

Thanks for your advice.

Sorry I haven't mentioned the config of my PC before.

Configuration:

Code:

CPU:
AMD Ryzen 5 3400G with Radeon Vega Graphics
1 physical process; 4 core; 8 threads

RAM:
30791648 KiB
Motherboard:
System Version/PRIME X570-P (ASUSTek Computer inc)

Graphics:
3840x2160
(Unknown)
The X.Org Foundation

There is no graphic card.

OS - Ubuntu 18.04
Old display - Dell 2K 25" display, working for years without problem.

I have brought the display back to the seller for testing. There was no flickering found in about 30min testing.

Tests made at home:
Reading documents - seldomly flickering. If clicking mouse to read another connecting document it may flicker occasionally.
Watching 4K YouTube video - no flickering
Watching other YouTube video - flickering occasionally

Regards

sgosnell · 10-08-2020, 09:27 AM

Make sure the refresh rate is correct. Some monitors at high resolutions use 30Hz instead of the usual 60Hz, and perhaps something in between. I get the exact symptoms described if my display settings are 60Hz, because the monitor wants 30Hz. Changing the display settings to either a different resolution, or to 30Hz at the highest, solves the issue.

ondoho · 10-08-2020, 03:04 PM

Quote:

Originally Posted by morning-tea

It flickers now and then occasionally, turning to a black screen and back in about 5 to 15 seconds. It happens sometimes automatically and another time when I click the mouse.

Are you saying it stays completely black/dark for 5-15s?
Can you reproduce the behaviour, or does it happen regularly, or is it completely "random"?
Is the screen/display/system/usability OK otherwise?

morning-tea · 10-08-2020, 03:48 PM

Quote:

Originally Posted by sgosnell

Make sure the refresh rate is correct. Some monitors at high resolutions use 30Hz instead of the usual 60Hz, and perhaps something in between. I get the exact symptoms described if my display settings are 60Hz, because the monitor wants 30Hz. Changing the display settings to either a different resolution, or to 30Hz at the highest, solves the issue.

Hi,

The problem mentioned happened unexpectedly. I don't know when it will come. Previously the refresh rate was set 60Hz and now I set it 30Hz to check whether the problem will happen.

Regards

morning-tea · 10-08-2020, 03:55 PM

Quote:

Originally Posted by ondoho

Are you saying it stays completely black/dark for 5-15s?

Yes

Quote:

Can you reproduce the behaviour, or does it happen regularly, or is it completely "random"?

It happened randomly beyond my control. I can't reproduce it.

Quote:

Is the screen/display/system/usability OK otherwise?

Sorry I don't completely understand your question. It is a brand new Dell 32" 4K display just purchasing it. The PC is working without problem, connected to a 25" 2K Dell display.

Regards

sgosnell · 10-08-2020, 05:57 PM

As I said, my LG 4k monitor is unstable at 3480x2160@60Hz, but it's fine at 30Hz. I'm not sure if that's the same with any other monitor. This is my first monitor capable of that resolution. It's too small for my old eyes anyway, so I run it at 2560x1440, and that's completely stable. It does come up at 3480x2160@60 for the login to the desktop, but it goes back to the correct settings immediately after logging in. If I leave it at the default highest resolution, the screen flickers and goes black for several seconds, returns, and that repeats until I change the resolution or refresh rate.

morning-tea · 10-08-2020, 08:17 PM

Quote:

Originally Posted by sgosnell

As I said, my LG 4k monitor is unstable at 3480x2160@60Hz, but it's fine at 30Hz.
- snip -

I have tried 3840x2160@30Hz almost without flickering. It flickered twice while I watched online YouTube video

Now I'm trying 3840x2160@50Hz to check and I'll come back to report.

If selecting 2K resolution, no flickering was found.

Regards

ondoho · 10-09-2020, 12:59 AM

Quote:

Originally Posted by morning-tea

Yes

All this does not sound to me like it could be fixed with screen reolution and/or refresh rates.
Something like a faulty wire or power supply sounds most plausible at this point.

morning-tea · 10-09-2020, 08:39 AM

Hi sgosnell,

Have run the display at 3840x2160@50Hz for half day. There was no problem found except in one occasion when I tried to print an online payment statement. The screen flickered to complete darkness in about 3~4 seconds twice and came back to normal again. Then I can print the statement to .pdf file and browse the online statement without further problem. It looks quite funny to me.

Tomorrow I'll try to run the display at 3840x2160@60Hz again to see what will happen.

Regards

morning-tea · 10-09-2020, 09:23 AM

Quote:

Originally Posted by ondoho

All this does not sound to me like it could be fixed with screen reolution and/or refresh rates.
Something like a faulty wire or power supply sounds most plausible at this point.

Hi ondoho,

This is a brand new display. I have brought it back to the seller. They tested the display and the HDMI cable at their shop for about half hour without problem found. There was no flickering on browsing online video nor reading documents.

I have a Dell 25" 2K display running for >10 years. At the beginning it also suffered occasional flickering problem. Then Dell provided me another HDMI cable and the problem gone. Now this display is still running strong without problem. I have connected it to this PC with no flickering discovered.

Regards

sgosnell · 10-09-2020, 10:12 AM

I have an excess of HDMI cables, and I went through all of them. The HDMI cable is not the cause of my issues. At the correct settings, the display is completely stable. Using unsupported resolutions/refresh rates results in repeatable problems. I can recreate the flickering and intermittent black screens at will by setting 3480x2160@60Hz, it's completely reproducible. I also get no video through a KVM switch until the display settings are set to something different. That is reproducible as well. I gave up trying to set the display before the desktop starts, and just run the HDMI cables to separate monitor inputs. I do not have this problem with the other computer, because it's not capable of the higher resolution. The newer computer apparently tries to use the highest resolution it's capable of, and the monitor can't handle it properly. I keep hoping that a newer kernel will solve it, but no joy so far, and I'm running Sid. With Buster backports there is no hope, and with the regular Buster kernel the computer won't even run a desktop. This is obviously, at least to me, a case of using the newest hardware available, to which the software hasn't yet caught up, but I suspected that I would have issues for awhile. I planned for this to be the last computer I buy, so I went for the newest hardware available, both the PC and the monitor. It will get sorted out eventually, I'm sure, and I can live with what I have for now.