LG -UD6100 Service Manual page 39

Checking Flow : Back Light
START
No
Check the U307 pin 5
Check & replace QSC
+VPWR
Yes
No
Re-Soldering or
Does U307 work Properly?
Replace U307
Yes
No
Check the signal level at
Replace QSC
LCD_BACK_EN=high?
Yes
LCD backlight will
work properly