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Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4. TROUBLE SHOOTING
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4.15 Keypad Backlight Troubleshooting
4.15.1 Main keypad backlight
Key Pad Back Light is on as below :
Key pressing KEY_BL_EN go to 2.7V MAIN Key Backlight LED On
Start
Change the Main board
Check battery
NO
Yes
Yes
Key press
Change the Main board
Yes
NO
+VPWR is above 3.2V?
KEY_BL_EN is 2.7 ?
R709 & R710 is
connected
ground ?
Yes
Change the KEY FPCB
NO
+VPWR
Figure .MAIN key backlight LED part
Rev.1.0.3
Rev.1.0.3
KEY LED
100ohm
R710
LD702
LEWWS44-E
R711
4.7K
3
1
PMST3904
Q701
2
LEWWS44-E
LD701
RSB6.8CST2R
VA714
RSB6.8CST2R
VA713
100ohm
R709
RSB6.8CST2R
VA712
+VPWR
KEY_BL_EN
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