the basic voltages of the source board 3.3v, 12 and 24V are normal . The LED on the source board flashes 6 times. I downloaded the service manual but couldn't find any references to the error code.

If the power supply and inverter are working, then either the processor or the memory are faulty.

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

factory reset Can be ?

Most likely the nand firmware is not for your panel. Try to upgrade via usb firmware from the official lg website. Or go into service mode and switch the panel there.