@samwilkins sounds like an issue with either the main board or the display panel itself. We will need to know your TV's exact model number. Next, unplug it and remove the back cover. Then do a visible inspection of the board. Check for any component that may look damaged, missing etc. Post some good pictures of your boards with your Question. That way we can see what you see and hopefully help you further. Also, tell us more about this "the screen has been too dark for ages." We will need to know if it was dark all over or just certain regions etc. The more details you can provide the better of an answer we can provide.
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