sound. ,changes channel,adjustable volumes but no light

Daniel Mburu  could be a backlight array error. In a darkened room, with the TV on, sound playing etc. shine a flashlight beam at an angle against the screen. If you can make out shapes etc. you know it is your backlight that is not working. Most common error for that is a failed backlight strip. Other than that you will have to remove the back cover from you TV and check the voltages on the power board etc. Since TCL Schematics etc. are virtually non-existent you will have to post some good images of all of your boards with your QUESTION. That way we can see what you see. 在已经存在的问题里加入图片

Of course, always check the warranty and see if this TV is still covered. If so, make use of that and get it fixed.