Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis. https://homenol.blogspot.com/
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main digital board./
More generic answers that don't really help .....
It takes 4 things to make the backlights come on..1st and this is generally the problem, some of the LED's are bad, and will need to be replaced but before cracking the panel open test the other things ...here they are...2nd is the proper voltage to the LED strips in the panel, you can test this with a volt meter to make sure they are what the legend on the board says the voltage should be but if you have shorted or open lamps in the panel then that voltage may start out correct for a second or so then drop to 0 because of over current or voltage, 2nd is you need a BL-On command, you can find that pin on the power supply board by looking at the legend on the board of the pin layout, if you don't have this voltage replace the main board and 4th is you need what is called a PMW (pulse width modulation)signal, its what tells the backlights how bright to be and this voltage needs to be between 1.5 and 5 volts...but if its 0 then the main board is bad as well and with it at 0 the backlights will barely glow, you wouldn't see it unless you pulled the panel apart...That is how you troubleshoot a LED lamp issue...Good luck!!
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