LG 55QNED85SQA Service Manual page 25

Standard Repair Process
Error
symptom
First of all, Check whether all of cables between board is inserted properly or not.
(Main B/D↔ Power B/D, Each Cable for Panel, Speaker Cable, IR B/D Cable,,,)
No video Normal
Normal audio audio
N
Move to No
video/No audio
※Precaution
☞A4 & A2
Always check & record S/W Version and White
Balance value before replacing the Main Board
A. Video error
No video/ Normal audio
☞A1
Y
Check Back Light
On with naked eye
☞A9
Check Power Board VLED output
Repair Power
Board or parts
☞A9
Y
Check Power board
On
12V etc.
N
☞A10
Y
Normal Error Check LED Driver
voltage Board by LED indicator
N
End
Replace Main Board
Established
date
Revised date
Y
Replace T-con/Main
Normal
voltage Board or module
N
Repair Power
Board or parts
LED
Y
Driver B'D
error
N
Replace Module
Re-enter White Balance value
1/17
Replace LED
Driver BD
End