What to do if the video output flickers?

Keywords: splash screen; video display; screen flicker ; Display problems Troubleshooting;

Applicable product model: All of the KVM switches,

like HKS0401A1U; HKS0401A2U; HKS0402A1U; HKS0802A1U; PKS0802A10; HKS0403A1U, etc.

📌If you are experiencing issues with flickering screens on external monitors connected to your TESmart KVM switch, you could try the following troubleshooting steps to check and solve it.

If the problem persists, please contact us on time. We have a professional after-sales service team to provide the best assistance.

Contact method:

1) Click "Contact Us" on the homepage and submit feedback

2) Click the chat window in the lower right corner or submit feedback

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

1. 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.

2. 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.}

3. 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.

4. 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.

5. Use cross-testing to confirm the final cause.

To check whether the problem is the KVM switch port, the connecting cable, or the output port of the computer and the input port of the monitor.

➡️Cross experiment method: At least one input source can be displayed normally.

Step 1. Please exchange the port position where the input source is connected with the KVM

(leave the cable unchanged)

🎯Cross test as shown in the figure.

Before: Assume that before the cross-experiment, PC1 is the splash screen monitor and PC2 is the working monitor.

PC1--->KVM PC1 input--->(splash screen)

PC2--->KVM PC2 Input---> (The screen displays normally.)

Result ①: PC1 and its cable --> KVM PC2 input --> (splash screen display) PC2 and its cable --> KVM PC1 input --> (The screen displays normally.) PC2, which Was working normally before, continued to work normally, while PC1 still had a splash screen. It means that the KVM input port is working properly. Therefore, the problem should be PC1's cable or its output port. Then please get to step 2. to check for more details.

Result②: PC1 and its cable --> KVM PC2 input --> (work monitor) PC2 and its cable ---> KVM PC1 input --> (splash screen display) PC2, which was working normally before, now has a splash screen, while PC1 works fine. It means that the KVM PC1 input port is faulty. Please contact us for further assistance Our team will help you solve your problem.

Step 2. Please exchange the input source cable used by PC1 and PC2 to connect to the computer.

(keep input source and product port unchanged)

🎯Cross test as shown in the figure.

Before: Assume that before the cross-experiment, PC1 is the splash screen monitor and PC2 is the working monitor.

PC1 ---> Input cable 1 ---> (splash screen)

PC2--->Input cable 2---> (The screen displays normally.)

Result ①: PC1 ---> Input cable 2 ---> (splash screen) PC2 ---> Input cable 1 ---> (Working Display) PC1 still has the flickering issue, while PC2 continues to display normally. It means that the cable connected to PC1 is working properly. You can try connecting it to another port on PC1, or provide us with the specific model ID of PC1 for further assistance.

Result②: PC1--->Input cable 2--->(Working Display) PC2--->Input cable 1---> (splash screen) The splash screen issue on PC1 has been resolved and now the screen displays normally. However, PC2, which was working fine before, is flickering now. It means there is a potential cable issue with PC2. We recommend that you replace the HDMI cable between the PC2 and KVM to resolve the issue.

➡️Cross experiment method: All input sources correspond to a monitor splash screen.

Please connect the switch cable to the KVM port.

(Keep the position of the monitor and cables unchanged)

🎯Cross test as shown in the figure.

Before: Assume that before the crossover experiment, Monitor1 Is a splash screen monitor and Monitor2 is a working monitor.

Monitor1 ---> Display1 output ---> (splash screen)

Monitor2 ---> Display2 output ---> (The screen displays normally.)

Result ①: Monitor 1 --> Display 2 Output --> (splash screen) Monitor2-->Display1 output-->(The screen displays normally.) result: Monitor 1 continues to flicker while monitor 2 continues to display normally. It means that the problem is not related to the KVM port, It will need further confirmation.

Result②: Monitor1 -->Display2 output -->(The screen displays normally.) Monitor 2 --> Display 1 Output --> (splash screen) result: If monitor 1 returns to normal display and monitor 2 goes to a flickering screen, there may be a problem with the KVM port. Please contact us for further assistance.

STEP2——Keep the connection state completed in STEP 1. Please replace the cable connecting the display to the KVM

(Keep monitor and KVM out ports unchanged)

🎯Cross test as shown in the figure.

Before: Assume that before the crossover experiment, Monitor1 is a splash screen monitor and Monitor2 is a working monitor.

Monitor1 ---> Display1 output ---> (splash screen)

Monitor2--->Display2 output---> (The screen displays normally.)

Result ①: Monitor 1 --> Display 2 Output --> (splash screen) Monitor2-->Display1 output-->(The screen displays normally.) result: Monitor 1 continues to display the splash screen while monitor 2 continues to display normally. Please contact us for further assistance.

Result②: Monitor1 -->Display2 output -->(The screen displays normally.) Monitor 2 --> Display 1 Output --> (splash screen) result: If monitor 1 returns to normal display and monitor 2 splash screen, there may be a problem with the KVM port. We recommend that you replace the HDMI cable between Monitor 2 and KVM with the HDMI cable connected to Monitor 2 to resolve the issue.

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)

🎯Each of the above steps is designed to solve some potential issues, so if you confirm the specific problem after a certain step of testing, you don't need to continue the subsequent troubleshooting experiments. You can contact us directly and share details of the troubleshooting you've done. It will be helpful for us to help you solve problems more efficiently. Thank you for your kind understanding and active cooperation.