There was no need to dismantle the entire TV thinking that the problem could be the LEDs. The defect was the nand. I bought a nand already recorded and updated for the tv to work. Now I am facing another problem. After assembling the TV I realize that the image is negative, the same thing when taking a photo with a camera and using the negative film of the image. I thought it could be the low level backlight but it wasn't. The backlight is at level 20 in the same way the brightness and contrast are at the maximum level.
It may be something wrong in the assembly of the TV or some adjustment that needs to be done. NOTE: this nand was recorded in the last update.


I tested the LED bars and all the LEDs on. How I set it up:
1) the cardboard is placed
2) place the plastic spacer pins
3) thick glass is placed, one side of which is smooth and the other side is rough
4) the plastic frame is placed all around the screen
5) the display is placed

after entering the service menu I selected the factory reset. When turning on the TV the image was no longer negative but I notice that at the top of the image it becomes lighter than at the bottom.

Then repair the TV backlight.

Today I decided to dismantle the TV again to check if by chance during the assembly I had not done anything wrong.
I believe that the cause of the image getting a little dark at the bottom of the screen is the glass panel (or acrylic panel) that is under the LCD display. Upon closer examination of the condition of this glass (or acrylic) panel, it is a little whitish. I was trying to clean with a kitchen sponge and when using the side of the more rough sponge, I ended up scratching the a little glass bit (acrylic). When I set up the TV again to test, the small part scratched with the sponge let the light emitted by the LED bar pass. I believe that the glass or acrylic is opaque making the image darker in this region.

Is there a way to clean or maybe eliminate this glass (or acrylic) panel using maybe an aluminum foil and vegetable leaf (the same material used in LG TVs)?

I was trying to clean the 90x51 mm acrylic sheet using a kitchen sponge, but I ended up making a mistake when using the rough part of the sponge. There is now a small scratched part of the acrylic. Is there a chance to recover the acrylic sheet using any method?