LG F1200 Service Manual page 54

(8) Keypad Backlight Trouble
• Backlight Operation
- The Keypad LED Backlight is controlled with KEY_BACKLIGHT signal from ABB (Syren)
- The LEDs are forward biased and turned on
• Check Points
- KEY_BACKLIGHT signal
- LEDs
• Trouble Shooting Setup
- Connect PIF-UNION Jig to the phone, and Power on
- Enter Engineering mode
- Go to menu "Baseband ➝ Backlight ➝ Keypad on"
• Trouble Shooting Procedure
- Check the soldering of components
- Check the KEY_BACKLIGHT signal
- Check LEDs
Check soldering !
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4. TROUBLE SHOOTING