Repair Flow Chart:Trouble Condition
Green Power is on, but LCD backlight is not on.
Backlight does not turn on, or only turns on and then off.
Power LED turns ON,
but LCD backlight is not ON
or only turns ON and then
OFF.
For Main
board:
Is the “BL_SW” voltage (3.3V)
Supplied from “K8B Pin13”?
For Power board:
Is the 0V supplied from “K703 Pin13”
during LED on?
The Panel is broken.
Replace “Panel”.
Main board can not work.
Replace “Main board”.
For Power board:
Is the 24V in “K703 Pin 1/2/3/4/5”
Power board can not work.
Replace “Power board”.
No:0V
Yes:3.3V
Yes:0V
No:over 0.8V
No:0V
Yes:24V
For Power board:
Is the BL-SW voltage (3.3V) supplied
from “K703 Pin12”
Confirm wire harness connection
between Main board and Power board.
No
Yes:3.3V
For Power board:
Is the BL-ADJ wave (PWM)from
“K703 Pin11” normally?
Confirm wire harness connection
between Power board and Main board .
No
Yes
The Panel is broken.
Replace the “Panel”.
Page 2
(TABLE *1.0) Main board: BL-SW Test Points
42" Models
BL-SW on
Main
board
Confirmation Voltage
P42142-00 Z5GH
P42142M-00 Z5GHM
P42142-02 Z5GK
P42142M-02 Z5GKM
Main
K8B Pin13
3.3V
(TABLE *2.0) Power board: BL-ERR Test Points
42" Models
BL-ERR on Power board
Confirmation Voltage
P42142-00 Z5GH
P42142M-00 Z5GHM
P42142-02 Z5GK
P42142M-02 Z5GKM
Power K703 Pin13
0V
