Chosen Solution
Sometimes, when we turn our TV on, the picture is very dark. It may take a few hours before it turns bright. This does not happen everytime, just at random and started within the past year or so. My model is 65UJ6300-UA
Jenalyn Momoa “the picture is very dark” how dark is dark? Do you have audio? Normal sound? If you have sound, then it does sound like your backlight is either not turning on, or you have a bad backlight array. This is an LG TV so the possibility of failed backlight strips is high. Of course, there is also the possibility that this is caused by a bad LED driver/power board. Tell us more about the dark picture. You can still see it shows very dark or how do you see it. You will need a multimeter and some screwdrivers. Unplug your TV and remove the back cover. Then take a couple of really good pictures of your boards and post those with your QUESTION. Adding images to an existing question this way we can see what you see.
Here is the service manual for your TV LG 65UJ6300 UA SM. Start with page 26 for the troubleshooting. If all of those are normal except you can’t see any backlights as described on page 45
then it is your backlight strips that have failed. They can be replaced.
