Question DisplayPort handshake issues causing lines and occasional burn-in

[Swordfish Designs]

Hello, and thanks to anyone who has input for me.

I have a custom build PC, here are my specs (initial build) and [current equipment].
ASUS ROG B550-I, Corsair RM650x
(Ryzen 7 5700G) [Ryzen 7 5800X]
(ASUS ROG 1050 Ti Strix) [ASUS Dual white 3060 Ti OC 8G]
Corsair Vengeance DDR4 3600 32GB
NVMe PCIe 4 1TB + 500GB
(Windows 10 Pro) [Windows 11 Pro]

Monitor : LG 27GL83A-B G-Sync compatible
DP Cables tried : LG OEM, iVanky VESA 4K, Silkland VESA16K, Amazon Basics VESA 8K
DP to HDMI VESA certified active converter with 4K Bell Canada VESA certified cable

The issue :
During the DisplayPort handshake between the PC and the monitor, there are static lines (usually horizontal) that appear on the monitor for a fraction of a second. They could be associated to the handshake itself occurring while the monitor tries to display the signal from the PC. These lines could be a few pixels wide at the top of the screen, or they could take up the whole lower half of the screen. On occasion, these flickers will lead to vertical or horizontal lines staying on the monitor. The backlight of the monitor seems to increase in brightness as the lines get brighter and brighter. If I do not unplug the power source from the monitor after a few seconds (max 10 seconds), the lines cause temporary burn-in. If I were to be away from the computer at the moment they occur, they would undoubtedly cause permanent damage to the monitor.

Timing of the issue :
The lines occur at the transition between the Windows boot screen to the login screen (the flicker can occur once or twice). The issue also occurs when activating or deactivating HDR in Windows settings, changing refresh rates and changing resolution. It also occurs often (but not always) at shut-down (when Windows has finished killing all its processes). It finally also occurs when resetting the computer after going in the BIOS menu.

The diagnostic process so far :
- Different DisplayPort cables, no impact.
- HDMI (PC) to HDMI (monitor) gives mitigated results - my HDMI cables do not permit HDR or anything over 100hz (monitor is native 144hz) and I have not been able to reliably reproduce the issue.
- Issue occurs while my 3060 Ti is installed, whether it be with my 5700G or 5800X CPU.
- 5800X has not IGFX, therefore to test if issue is present without a GPU installed, I reinstalled the 5700G without any discrete GPU, and the issue occurs using on-board DisplayPort.
- MemTest declared no issues with the RAM. RAM has been reseated, and DIMMA and DIMMB swapped. CPU reseated when swapping between CPUs. All power connectors (PCIe, ATX and EPS both on peripheral as well as power supply sides) reseated.
- All possible options in the BIOS that could impact power delivery or hardware compatibility have been played with, including CMOS reset and BIOS update to latest version.
- All NVidia options that affect G-Sync, active-sync, resolution, color depth, V-Sync, etc. have been played with.
- Use of an Acer 1080P 75hz monitor with DisplayPort to HDMI adapter, I get the flashing lines at the DisplayPort handshake, but no lines causing burn-in. HDMI connection on both ends seems to have a slower handshake, and no lines at all appear during the process.
- Hours of intensive graphical use (gaming at 1440p 144hz with and without GPU overclocking) does not suffer from this issue.

Repair processes :
Seeing as the issue is, at first glance, the monitor itself, I have had the unit serviced under warranty by an LG authorized service center. The gentlemen that work there have a very square attitude towards customers. They ask for the symptoms, but refuse to listen to any type of diagnostic the client has tried. They ended up replacing the main board of the monitor twice, as the issue has not been impacted by the first repair. The issue is still present after the second main board change. When I tried to inquire about their diagnostic process, they said they were not able to replicate the issue (even though I showed them video of the lines and burn-in). They said they simply connect the monitor and run basic tests. They DO NOT go play in "fancy settings" (when I brought up HDR switching). They ended the conversation on "LG told us to change the main board so we did."

Further diagnosis is to come, but I had brought the whole system to a computer repair center, and even in their shop, they were able to reliably reproduce the issue. They said their initial impression is a bad monitor (this was after the first main board change). They said they wouldn't be surprised if the new main board were defective.

After a second main board, my questions to you are as follows :

- Is the screen flicker at DisplayPort handshake normal?
- Is there another component in that monitor that could be defective?
- If the monitor is not the issue, what other component could it be, seeing as the issue is present with or without the GPU?

Thanks for your time!! I appreciate it. This issue has been driving me mad for months... I'm going down the rabbit hole on this one.

 

[Ralston18]

Monitor had no problems at the shop - correct?

Are you able to try the monitor somewhere else: family, friend, work?

At home:

Take a look at the electrical connections: outlets, switches, power strips, surge protectors, speakers, amps, and other devices as applicable.

Sketch out a diagram showing all devices, ports along with all connecting cables power, audio, video, network.

Look for loops: Device A connected to Device B connected to Device C connected to Device D connected to Device A again.

Any sort of loop.

My thought being that there could be a ground loop.

 

[Swordfish Designs]

The monitor did exhibit the issue at the repair shop.

By brother (network engineer) knows an electronics engineer (worked on monitors among other things) who says that following all this diagnosis, he suspects either a bad powe board or power adapter - he thinks that there is overpower being fed to the monitor, causing the issue at the handshake.