LG GW520 - Keypad Backlight Trouble

- 84 -
LGE Internal Use Only Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
5. Trouble shooting
GW520 service manual
5.8 Keypad backlight Trouble
Start
END
Check soldering of
LD400~LD403, R439
R442, R444, R445
Is the level of
QWERTY_KEY_BL low?
Check TP1
Is signal QWERTY_KEY_EN
Low?
Check TP2
Resolder LD400~LD403,
R439, R442, R444, R445
YES
YES
YES
Does backlight work well?
YES
NO
NO
NO
Change the Main Board
Change the Main Board
Change LD400~LD403
And check again.
Work well?
NO
YES
Checking Flow
Start
END
Check soldering of
LD400~LD403, R439
R442, R444, R445
Is the level of
QWERTY_KEY_BL low?
Check TP1
Is signal QWERTY_KEY_EN
Low?
Check TP2
Resolder LD400~LD403,
R439, R442, R444, R445
YES
YES
YES
Does backlight work well?
YES
NO
NO
NO
Change the Main Board
Change the Main Board
Change LD400~LD403
And check again.
Work well?
NO
YES
Checking Flow
Circuit DiagramCircuit Diagram
47R442
LD403
LEWWS44-E
47R445
ICVN0505X150FR
VA403
VBAT
R444 47
R439
LD402
47
LD401
LEWWS44-E
LEWWS44-E
LD400
EDLH0013701
LEWWS44-E
QWERTY_KEY_BL