Samsung SGH-X640 Service Manual page 42

Flow Chart of Troubleshooting
13. GSM Transmitter
TX ON (5Level)
Yes
U103 Pin7
>= 20dBm
No
U103 pin11
>= 20dBm
No
U102 pin6
>= 20dBm
No
U102 pin48
>= 3dBm
No
OSC101 pin1
>= 6dBm
No
U100 pin6, 7, 8, 9
>= 500mV
No
Check U200
END
Yes
Yes
Yes
Resolder L113,L114,C151
Yes
Yes
Yes
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Resolder CN100, C144
Check U103
pin4 = H (2.68V),
pin2,8 = L
No
Check U102
VBATT, pin42,43
OK?
No
Resolder R123
Check U100
pin4 >= 4.0V
pin22,28 >=2.7V
OK?
Yes
7-18
Yes
Change or Resolder U100
Check ANT Switch
control circuit
Yes
Resolder or Change U102
or check PAM control signal
Check +VBATT
No
Check & Resolder
RF PSU Part
Resolder U100
or check Txcpo(R114)