You need the service manual since that will contain what test points to measure as well as what boards supply the LED power as well as control the LED strips. Without the manual you are guessing.
I have the following tv above that has picture and sound but no backlight. I have replaced the main power supply board and LED lights and still the same thing. I made sure that the LEDs worked by using a 9v battery to power them and they all light up. I’m at a loss at this point. Not sure if I should try the T Con board or the main board since those are the only 2 boards left in the tv. Any help or advice would be greatly appreciated!