i dont know this exact model, but i can advice you based on a slightly diffrent model. i hope the solution will be valid for your model as well:
TV is digital controlled and have to be adjusted via service menu
except the external focus and screen on back of (flyback) high voltage transformer.
This is one you can try: Need plastic allen or plastic small flat
blade screwdriver to fit these. Focus is top, bottom is the screen
that set the overall brightness. Before adjusting, go in menu: press menu once, select picture quality, I think number 4, press 2 for "preset..", press 2 again to select normal. Back out by pressing zero repeatedly. It may ask you to save new settings, select yes.
If screen is adjusted too bright, picture look lousy (washed out) the blacks will light up (becomes grey, or visible lines) this means you have actual fault that prevents you to get decent pix, that when it is time to take it in for repair.