Backlight dead,display&touchscreen working fine

Hi, got a tab 3 with not working backlight. Touchscreen and display seems to be working fine though. Seeing display under a lamp is bit challenging seems ok. Touchscreen,wifi,sound,buttons lights , all seems to be without a problem, only tat backlight.

Tried :

>restarting,

>factory defaults ,

>changing the screen brightness settings,

>battery saving,

>charging to 100%

>desattaching and reattaching +cleaning the 3 ribbon cables from mainboard too.

Is there some simple solution to checking out if the insides/LED backlights work before ordering complete new screen or checking the bugs on mainboard? Allegedly no water or falling damage sustained.

Thanks in advance for every help.