Keypad Backlight Troubleshooting - LG CU920 Manual

4.15 Keypad Backlight Troubleshooting

Key Pad Back Light is on as below :
Key pressing → LED_CON go down low (below 0.8v) → MAIN Key Backlight LED On
Start
Key press
+VPWR is ab ov e 3.2V?
LED_CON is low?
R102 & R103 is
conne cted ground ?
Chang e th e Main bo ard
Figure. Side key FPCB backlight LED part
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Only for training and service purposes
NO
Yes
NO
Yes
NO
Yes
LED_CON
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4. TROUBLE SHOOTING
Check ba ttery
Yes
Chang e th e Main bo ard
Chang e th e KEY FPCB
KEY LED
LGE Internal Use Only