@bazzdog sounds like your TV has issues with the power board not supplying the voltage for your backlight, your T-con board having failed or your backlight array failing. Unplug your TV and remove the back. Then take a look at all the boards. Check for obvious damaged components like leaking or domed looking capacitors. Check to ensure that all the wires are properly connected. Once you checked that, take some good pictures of your boards and post those with your question. Use this guide Adding images to an existing question for that. It will allow us to see what you see. You will need a multimeter to check the proper voltages so let us know what you find thus far.