Samsung SGH-X640 Service Manual page 29

3. Charging Part
Abnormal charging part
Yes
Check the C508
> 4.9V
Yes
U502 pin 5 = "H"?
Yes
U502 pin = "L"?
Yes
Check the C507
≒ 4.2V
Yes
END
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No
Check the the circuit related to
No
Resolder or replace U502
No
Check the circuit related to
No
Resolder or replace U502
7-5
Flow Chart of Troubleshooting
V_EXT_CHARGE
CHG_ON signal