From one day to the next, this LG TV model 43UH6100 showed purple stains all over the screen. After a quick test and some research the problem seems to be the backlight panel. The only way to be sure is to disassembly the TV, this can be quiet hard since some parts are tightly closed. I recommend you to look for a video for your exact TV model and a patience.

Once you get the back cover removed and unscrew a couple of screws you will find the the backlight. To test the LEDs unplug the connector as shown on the picture then you will need to apply 3 Volts to the terminals of each as shown in the figures below, I used 2 batteries of 1.5 Volts each and some wires.

The replacement parts finally arrived. After replace the three damaged led strips and assembly the TV again there is no purple spots on the screen as it can be seen on the pictures.