Samsung SGH-X640 Service Manual page 31

4. Sim Part
Phone can't access SIM Card
CN400 pin 1,5 = "H"?
Check SIMCLK Signal on CN400
pin3 in a few second
After SIM card insert,
CN400 pin 2 = "H(SIM_RST)"?
Check the SIM Card
Yes
Yes
After Power ON,
Yes
Yes
Yes
END
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No
Check the sim charge pump
No
No
7-7
Flow Chart of Troubleshooting
Check the 32k OSC
Replace PBA