LG C3400 Service Manual page 81

4. Troubleshooting
CIRCUIT DIAGRAM
Checking Flow
VBAT
KEY BACKLIGHT
R373 12K
KEY_BACKLIGHT
R364 C340
12K 27p
Is the level at R390
YES
Are all LEDs
Working?
YES
Backlight will work properly.
VBAT
Q301
IMX9T110
START
NO
High?
NO
- 80 -
Check U101
Check the soldering
each R and LED
NO
Replace or resoldering
component