LG KU250 Service Manual - Page 104
Keypad Backlight Troubleshooting
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4. TROUBLE SHOOTING 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? Yes KYBD_BACKLIGHT is 0V ? Yes Backlight LED ON? No Change the Main board NO NO YES Check battery Yes Change the Main board END +VPWR KEY_BACK_LIGHT LED(8EA) +VPWR LD400 LEBB-S14H LD403 LEBB-S14H LD406 LEBB-S14H REV_B : EDLH0013501 --> EDLH0006001 R411 100ohm R414 100ohm R417 100ohm KYBD_BACKLIGHT LD404 LD407 LEBB-S14H R415 LEBB-S14H 100ohm R418 100ohm LD402 LEBB-S14H LD405 LEBB-S14H R413 100ohm LD408 LEBB-S14H R416 100ohm R419 100ohm Figure.Keypad backlight LED part - 105 -
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4. TROUBLE SHOOTING
- 105 -
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
Figure.Keypad backlight LED part
Start
Change the Main board
Check battery
NO
Yes
Yes
Key press
Change the Main board
Yes
NO
+VPWR is above 3.2V?
KYBD_BACKLIGHT is 0V ?
Backlight LED ON?
No
END
YES
+VPWR
KEY_BACK_LIGHT LED(8EA)
REV_B : EDLH0013501 --> EDLH0006001
R418
100ohm
100ohm
R415
100ohm
R411
R413 100ohm
LD408
LEBB-S14H
LEBB-S14H
LD405
LD406
LEBB-S14H
R414
100ohm
LD400
LEBB-S14H
100ohm
R417
LD404
LEBB-S14H
LEBB-S14H
LD403
100ohm
R416
LEBB-S14H
LD402
R419 100ohm
LEBB-S14H
LD407
+VPWR
KYBD_BACKLIGHT