Dual/Triple Monitor KVM Switch all black screens

Keywords: Display; Blackout; Dual Monitor KVM switch; Triple Monitor KVM Switch

Applicable product models: Dual/Triple Monitor KVM Switch



If you're encountering problems where none of the external monitors connected to your TESmart KVM switch are displaying (showing a black screen), 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.

We provide detailed troubleshooting steps below for the situation where all monitors display black screens. Please refer to the following suggestions for assistance:
  1. Input and output issues, docking station compatibility, and cable problems:

Please try connecting the problematic monitor directly to the computer (bypassing the KVM) and check if the issue persists. If the monitor still doesn't work, it suggests that the problem may lie with the source, monitor, cable, or docking station. It's important to keep the original cable or connected converter unchanged during this testing process.

  1. Docking station/adapter issues:

Have you used any adapters or docking stations to connect the computer and monitors to the KVM switch? If so, check the signal direction of the adapters or try using a different adapter. The correct signal transfer direction is from the computer to the KVM switch and then to the monitor. For example, if the input source port is USB-C and the KVM port is HDMI, the appropriate converter to use is USB-C to HDMI, not HDMI to USB-C.(If all external monitors can display normally when directly connected (bypassing the KVM switch), please proceed to the next troubleshooting step.)

  1. Resolution of the monitor:

  1. 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.

  2. 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".

  3. 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.

  1. Check for monitor recognition issues:

If the computer recognizes the name of the KVM instead of the name of the monitor, the output port of the product may be abnormal. If the computer does not recognize any name, the input port of the product may be damaged. (Does not include PKS0802A10)

  1. 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.


➡️ Cross-experimentation method: At least one of the input sources can display properly.

  • Step 1. Please swap the position of the port where the input source is connected to the KVM

(keep the cable unchanged)

🎯Cross testing as shown in the figure.

Before: Assuming that before conducting the cross-experiment, PC1 shows a black monitor, PC2 is the working monitor.
PC1--->KVM PC1 Input--->(Black monitor)
PC2--->KVM PC2 Input---> (The working monitor )

Exchange the connection port on switch only.jpg


PC1 & its cables -->KVM PC2 Input-->(Black monitor)

PC2 & its cables-->KVM PC1 Input-->(The working monitor )



The PC2, which was previously displaying normally, continues to function properly, while the PC1 is not displaying anything. This confirms that the KVM input port is functioning properly. Thus, the cause of the problem might be the PC1's cable or its output port. Therefore, further investigation is necessary. Please go to step 2.


PC1 & its cables-->KVM PC2 Input-->(The working monitor)

PC2 & its cables--->KVM PC1 Input-->(Black monitor)



The previously functional PC2 is now not displaying, while the PC1 can work correctly. This indicates a malfunction in the KVM PC1 input port. Please reach out to us via the chat window at the bottom right or by submitting feedback for further assistance. Our team is available to help you troubleshoot the issue.

  • Step 2. Please swap the input source cables connected to the computer.
(keep the input source and product port unchanged)

🎯Cross testing as shown in the figure.

 Before: Assuming that before conducting the cross-experiment, PC1 shows a black monitor, PC2 is the working monitor.

PC1--->Input cable1 --->(Black monitor

PC2--->Input cable2---> (The working monitor

exchange cables.jpg


PC1--->Input cable2 --->(Black monitor

PC2--->Input cable1 ---> (The working monitor



The black screen issue persists with PC1, while PC2 continues to display normally. This suggests that the cable connected to PC1 is functioning properly. You can attempt connecting it to another port on PC1 or provide us with the specific model ID of PC1 for further assistance.


PC1--->Input cable2 --->(The working monitor

PC2--->Input cable 1---> (Black monitor



The black screen issue on PC1 has been resolved and it now displays normally. However, PC2, which was previously working fine, now has a black screen. This indicates a potential cable problem with PC2. We recommend replacing the HDMI cable connected to PC2 to fix the issue.

Dual Monitor KVM Switch Only one monitor can display

  1. If you have at least 1 video connection from each computer then using the Mode 2 feature (each computer on each monitor) you can test the KVMs output to the monitors. Both displays should work when Mode 2 is active. This confirms the KVM output is working fine. Further investigation is needed to determine whether the issue lies with the KVM input port or the input cables.

  2. If you have only one monitor working, it's likely that you're missing the second video connection or the dock/adapter you're using is incompatible. Even if the adapter works when not connecting it to the KVM, it is possible that the adapter does not work well in the KVM environment.

  • Firstly, try connecting your computer to 2 monitors at the same time (bypassing the KVM) and check if the problem persists. If the monitor still does not have a picture, this indicates that the problem may be with the source, monitor, cable, or docking station. Be sure to leave the original cable or connected converter intact during this test.

  • Secondly, how to determine whether the issue lies with the part connecting to the KVM including KVM ports, and input/output cables?

Please take the following cross-experimentation methods to troubleshoot specific problems. For detailed crossover experiments, please jump to this link.


Each of the following steps is designed to troubleshoot a potential problem, so if you have confirmed the problem after a certain step of testing, you do not need to continue with the subsequent troubleshooting experiments. Contact customer service through online chat or email and explain the troubleshooting you have done. Their assistance can help you resolve the issue more efficiently, saving you time and money.

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