LG 42LA86 Series Service Manual page 91

Standard Repair Process
LCD TV
symptom
First of all, Check whether all of cables between board is inserted properly or not.
(Main B/D↔ Power B/D, LVDS Cable,Speaker Cable,IR B/D Cable,,,)
No video
Normal
Normal audio
audio
N
Move to No
video/No audio
※Precaution ☞A7 & A3
Always check & record S/W Version and White
Balance value before replacing the Main Board
A. Video error
Error
No video/ Normal audio
☞A1
Y
Check Back Light
On with naked eye
Check Power Board 24v output
☞A2
☞A4
Y Check Power Board
On
12v,3.5v etc.
N
Replace Inverter
Y
Normal
or module
voltage
N
Repair Power
Board or parts
Replace Main Board
Established
2012. 12 .06
date
Revised date
Replace T-con Board
Y
Normal
or module
voltage
And Adjust VCOM
N
☞A28
Repair Power Board
or parts
End
Re-enter White Balance value