Keypad Backlight Trouble - LG MG180C Service Manual

4. TROUBLE SHOOTING

4.11 Keypad Backlight Trouble

Block Diagram
Backlight Operation
• The keypad LED backlight is controlled with LEDB signal.
• Keypad_Main signal from DBB.
• The LEDs are forward biased and turned on.
Trouble Shooting Setup
• Connect PIF-UNION to the phone, and power on.
• Enter the engineering mode.
• Go to menu. "Baseband → LED → Backlight → Keypad on"
Trouble Shooting Procedure
• Check the soldering of components
• Check the LEDB signal
• Check LEDs
Check Points
• LEDB signal
• LEDs
VBAT
KEY BACKLIGHT
R309 R312 R313
R307 R308 R310
200 200
200 200 200 200
LD302 LD303 LD304 LD305
LD300 LD301
R320
LEDB
10
- 60 -
R314 R315 R316 R317
200 200 200 200
LD306 LD307 LD308 LD309
VA305
EVL5M02200