Keypad Backlight Troubleshooting - LG U250 Service Manual

4.14 Keypad Backlight Troubleshooting

Key Pad Back Light is on as below :
Key pressing → KYBD_BACKLIGHT go to 0V → MAIN Key Backlight LED On
Start
Key press
+VPWR is above 3.2V?
KYBD_BACKLIGHT is 0V ?
Backlight LED ON?
Change the Main board
REV_B : EDLH0013501 --> EDLH0006001
KYBD_BACKLIGHT
NO
Yes
NO
Yes
YES
No
KEY_BACK_LIGHT LED(8EA)
+VPWR
LD400 LEBB-S14H
R411
100ohm
LD403 LEBB-S14H LD404
R414
100ohm
LD406 LEBB-S14H LD407
R417
100ohm
Figure.Keypad backlight LED part
- 105 -
4. TROUBLE SHOOTING
Check battery
Yes
Change the Main board
END
+VPWR
LD402 LEBB-S14H
LEBB-S14H LD405 LEBB-S14H
R415
100ohm
LEBB-S14H LEBB-S14H
LD408
R418
100ohm
R413 100ohm
R416 100ohm
R419 100ohm