Backlight dead, touchscreen works fine

Hi, got a tab 3 with not working backlight. Touchscreen works fine though. Seeing display under a lamp is bit challenging but seems that the rest is working just fine. Touchscreen,wifi,sound,buttons light,all seems to be working fine. Tried restarting,factory defaults ,changing the screen brightness settings, battery saving, charging to 100% with no luck.

I tried desattaching and reattaching 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.