Samsung SGH-X640 Service Manual page 41

12. GSM Receiver
RX ON
RF input : CH center freq
Amp : -50dBm
Yes
U103 Pin7
>= -65dBm
Yes
U103 pin5
>= -65dBm
Yes
F100 pin1
>= -70dBm
Yes
U100
pin32 >= -70dBm
pin33 >= -70dBm
Yes
U100 pin6, 7, 8, 9
>= 1V
Yes
R116, R117, R119
R121 >= 1V
Yes
Check U200
END
No
No
No
Resolder F100, C104, L103
No
Resolder L100, L101, L102
No
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Resolder CN100, C144
Check U103
pin4 = L, pin8 = L
Yes
Check U100
pin10,22,28 >=2.7V
pin20 >=4.0V
Yes
7-17
Flow Chart of Troubleshooting
No
Check ANT Switch
control circuit
Resolder U103
No
Check & Resolder
RF PSU Part
Check &Resolder
U100, RF26MHz part,
R100, R101