LG 28LJ400B Service Manual page 31

Standard Repair Process
10 Power supply for LED drive
A7 Power supply for LED drive
No backlight
Y
Check if
Y
LED output
short/open
Y
Remove
Correct
short/open
the LED
status
cable
IR indicator light
up but backlight slake
Check if LED output cable
is connect correction
N
Check PWM_DIM Control signal
Y
check is part of check is all of
the brightness is the brightness is
in dim status
in dim status
N
Check if UB801 PIN1
voltage is about 12V
Y
Check QB801/DB801
damage or not
Y
Change
QB801/DB801
6 12 31
N
Increase
Y
brightness/check
if Sampling
resistor is right
N
Check
Main
board
Change UB801
function
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