I have a dim/dark area in the center

@haxin looks like your panel is EDGE LIT and your backlight LEDs are failing. Time to replace those. Bit of a PITA since you pretty much have to disassemble your TV and your panel.Not to complicated just tedious.

The most complicated part will be the panel. You have to avoid letting it bend as you work on it. You'll be surprised how thin teh LCD really is and how much it loves to flex :-) Also, make sure that mark the diffuser sheets as well as the polarizers etc. Mark them exactly as they get removed. You can not flip them around etc. (otherwise you will have to wear polarized sunglasses to watch your TV. Been there done that :-)

Once you have your back cover off, post some pictures of what your TV looks like so we can guide you further, if needed. Once you have the back removed there will be a label on your lcd panel. Use that instead of the TV's model number to look for teh backlight strips.

在已经存在的问题里加入图片

Having your own question is way better than to threadjack ;-)