Sharp GX20 Service Manual page 61

10. "No Service" display and receiving/transmitting do not function.
10.1. "No Service" display and receiving/transmitting do not function in the EGSM band.
[Checkpoints for GSM tester transmission]
Fixed line: During input of –70 dBm.
After replacing the main PWB unit with normal one, trans-
mission with GSM tester possible?
After replacing FPC (flexible printed circuit) with normal
NO
one, transmission with GSM tester possible?
[Checkpoints in RF Test Tool]
[Transmitting System]
Is transmission possible using RF Test Tool?
YES
Voltage applied to VCO971 7 pin?
Is VCO971 frequency fixed at 4 times as the EGSM-band
transmitting frequency + 80 MHz (or 82 MHz)?
IQ Signal input to IC901 20, 21, 22, and 23 pins?
Voltage applied to VCO851 11 pin?
EGSM-Band Transmitting frequency input to IC831 1 pin?
EGSM-Band Transmitting frequency input to FL801 11
pin?
EGSM-Band Transmitting frequency input to J801 1 pin?
J801 defective.
[Receiving System]
Fixed line: During input of –70 dBm.
Voltage applied to VCO971 7 pin?
Is VCO971 frequency fixed at 4 times as the EGSM band
receiving frequency?
EGSM-Band Receiving frequency signal applied to IC901
10 and 11 pins?
EGSM-Band Receiving frequency signal output from
FL801 7 pin?
EGSM-Band Receiving frequency signal input to FL801 9
pin?
J801 or FL817 defective.
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CONFIDENTIAL
NO
NO
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
2 – 55
IC104, IC102, CN201, CN202, or PWB defective.
YES
FPC defective.
YES
NO
IC202, IC303, Q304, or Q308 defective.
IC901, VCO971, FL971, TCX951, or IC304 defective.
NO
NO
IC104, IC102, or PWB defective.
NO
Q304 or Q309 defective.
NO
VCO851, IC901, or IC993 defective.
FL811, R811, IC831, IC881, or IC992 defective.
NO
NO
IC991, IC992, IC993, FL801 or FL817 defective.
NO
IC202, IC303, Q304, or Q308 defective.
IC901, VCO971, FL971, TCX951, or IC304 defective.
NO
IC104, IC102, IC901, or PWB defective.
YES
FL901 defective.
YES
IC991, IC992, IC993, or FL801 defective.
YES
GX20