If your Xiaomi TV has sound but no picture, you should first check the backlight and try resetting the TV by unplugging it. For external devices, ensure they are powered on, connected properly, and the correct input is selected.
Here's a more detailed breakdown for your reference:
The TV may not support decoding the currently playing video resources. Please install a third-party player on Xiaomi TV to decode video image files.
Check the backlight. Shine a flashlight on the screen while the TV is on to see if you can faintly see an image or shadows. If you see faint images, it likely indicates a backlight issue, which may require professional repair or replacement.
Unplug the TV from the power outlet and let it sit for a few minutes (e.g., 5 minutes). Then, plug it back in and turn it on. This can sometimes resolve temporary glitches.
Check External Devices and Connections. Make sure any external devices (like DVD players, gaming consoles, etc.) are powered on and properly connected to the TV with the correct HDMI cable.
If none of the above steps resolve the problem, it's best to contact Xiaomi customer support or a qualified technician for further assistance.