keyboard backlight stop working, already tested led's found no problem

my keyboard backlight just stop working, i have already tested the individual led's that supposed to light up the keyboard with the help of a multi tester and found no problem with them. also check the connectors that run through the logic board and found nothing. any help with this? i don't consider buying an upper case or top case which houses the keyboard. because on my own diagnosis i think that there might be some lose ends within the logic board connector. did someone had ever encounter this problem before? please help.

thanks and regards