What to do if the video output flickers?

If you encounter screen flickering on the external monitor connected to the TESmart KVM switch, we suggest trying the following troubleshooting steps. If the issue persists, please reach out to the TESmart Customer Service Center for further assistance. You can contact us through the chat window at the lower right or by submitting feedback. Our dedicated team of professionals is ready to help and provide after-sales support.

Applicable product models: Dual/Triple Monitor KVM Switch

HKS202-E23 (Previously HKS0402A1U)/HDK202-E23 (Previously HDK0402A1U)/
HKS202-P23 (Previously HKS0202A2U)/HKS402-P23 (Previously HKS0402A2U)/
HKV202-E23 (Previously HKV0402A1U)/HKS802-E23 (Previously HKS0802A1U/
DKS802-E23 (Previously PKS0802A10)/HKS0403A1U etc.

This article includes the following topics:

For all monitors displaying a flickering screen, we have provided detailed troubleshooting steps below. Please refer to the following suggestions for assistance:

Input and output issues, dock compatibility, and cable issues:

Please try connecting the problematic monitor directly to the computer (bypassing the KVM) and check if the problem persists. If the display still doesn't work, the problem could be with the source, display, cable, or docking station. It is very important to keep the original cable or connected converter intact during this testing.

Dock/adapter is a mismatch:

If you use some adapters or docking stations when you connect KVM, please check if the signal direction of the adapter is right. The correct signal direction is from the computer to the KVM switch and then to the monitor. For example, if the source port is USB-C and the KVM port is HDMI, the appropriate adapter to use is USB-C to HDMI, not HDMI to USB-C. {If all external monitors display fine when connected directly (bypassing the KVM switch), proceed to the next troubleshooting step.}

Display resolution:

  • The output resolution of the cable is limited and the appropriate resolution is not transmitted. Please try lowering the output resolution of your computer. If the problem has been solved after that, then you can try to change to better quality connection cables.
  • Computer output capabilities are limited. It is recommended that you refer to your computer's official website to check the specifications. For example, some older PCs may not support outputting two 4K 60Hz video signals simultaneously, but they should be able to handle two 1080p signals without issue. In this case, lowering the resolution usually solves the problem.
  • The EDID reading is abnormal. It means that the video signal being output exceeds the recommended resolution and refresh rate. This usually happens when the monitor's optimal resolution refresh rate is higher than the KVM's optimal resolution refresh rate. "To confirm this problem, you can judge by comparing the output parameters of the expansion screen when connecting directly and through KVM; or through professional EDID reading software to confirm(you can consult customer service to get it). In some cases, the problem can be solved by hot-plugging the input cable on the PC side or restarting KVM".
  • The actual output video signal bandwidth exceeds the maximum bandwidth supported by the intermediate device. It will happen when the input source device and the monitor support the G/F-Sync function at the same time. Please try to turn off the HDR10, G-Sync, and FreeSync of the device.

Cable issues, like length or quality.

The cable exceeds the specified length, or the quality is not good, which may cause a flickering screen. Please try to change to better quality cable. Check if the length of the HDMI/DP cable meets the specifications below. Because the corresponding cable length will directly affect the output resolution.
Our KVM is equipped with a 1.5m 4k@60hz HDMI input cable.
  • When using 4K@60Hz as the input source, the output HDMI cable should be less than 5 meters.
  • When using 4K@30Hz as the input source, the HDMI cable at the output end should be less than 10 meters.
  • When using 1080@60Hz as the input source, the output HDMI cable should be less than 15 meters.

For the DP cable, it is recommended not to exceed 1.8 meters.

Final cross-experimentation method:

The aim is to determine the root cause of the issue, whether it is with the computer's output port, the connection cable, or the KVM switch port.

For more information about cross-testing, please click on the cross-testing

Other video problems: (snow screen, intermittent black screen, stuttering)

The signal source is abnormal when performing a certain operation, such as playing a certain video or playing a game

  • It may be that the converter used by the audio does not support HDCP, you can replace the converter to see if the problem is solved.

  • The game enhancement mode is not supported under the current output resolution. You Could try to reduce the output resolution or purchase a higher version converter.

  • The converter or docking station does not support G-sync and F-Sync (it can only be realized when the input source device and the display support the G/F-Sync function at the same time, which will cause the actual output video signal bandwidth to exceed the maximum bandwidth supported by the intermediate device)

If all of the steps above cannot help you locate and resolve the problem, please contact TESmart Customer Support for further assistance. Briefly mention the steps that you’ve already tried for a faster solution.






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