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2-3
SCH-A302
Trouble Shooting
1-3. Abnormal Backlight Operation
Y
‘L’ level outputted
from U501 pin1?
Check U501 pin1 and its neighboring
circuits. Replace if required.
N
Y
‘L’ level outputted
from U501 pin2?
Check U501 pin1 and its neighboring
circuits. Replace if required.
N
Press any button on the phone
Backlight LED on
1-4. Abnormal Key Data Input
Y
Scanning signals
outputted from U609 pins C2,
A3, E4, D3, C1?
Check keypad dom switch.
Replace if required.
N
Check initial status
END