Voxtel GSM ST11, Service Manual

Page: 37 / 60

5.14 RX Sensitivity Trouble (E-GSM)
5-16
Troubleshooting
YES
START
NO
YES
NO
NO
Check
RF connector ANT101 pin 2
frequency & power.
Frequency = 947.4 MHz?
Power -72dBm?
Set
• Phone : Test mode
62CH, 7level (TCH)
62CH, -60dBm (BCCH)
•Spectrum analyzer as shown in Remarks.
•Oscilloscope as shown in Remarks.
Check ANT101 soldering and short.
Replace ANT101 if defective.
Check :
• U110 soldering
• U110 pin 2 = Low voltage
• U110 pin 11 = Low voltage
Replace U110 if defective.
Check U201 soldering.
Replace U201 if defective.
Check
ANT switch U110 pin 10
frequency & power.
Frequency =947.4MHz?
Power -75dBm?
Check
RF 1'st SAW Filter U201 pin3,4
frequency & power.
Frequency = 947.4MHz?
Power -77dBm?
YES
NO
Check U206 soldering.
Replace U206 if defective.
Check
RFLO VCO U206 pin23,24
frequency & power.
Freuency =1894.6MHz?
Power -60dBm?
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Go to C
Remarks
1. Spectrum analyzer : SPAN = 1MHz
VBW = 1MHz
RBW = 3MHz
Press the trace button of spectrum analyzer on checking test
point and press the max hold of spectrum analyzer
2. Oscilloscope : 500mV/div, 2ms/div
3. RF Cable Loss : about 10dB