Voxtel GSM ST11, Service Manual

Page: 39 / 60

5.15 RX Sensitivity Trouble (DCS)
5-18
Troubleshooting
START
Go to D
YES
YES
NO
NO
Set
• Phone : Test mode
700CH, 2 level (TCH)
700CH, -60dBm setting (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
RF connector ANT101 pin 2
frequency & power
Frequency = 1842.8 MHz?
Power -73dBm?
Check
ANT Switch U110 pin 1
frequency & power.
Frequency = 1842.8MHz?
Power -76dBm?
YES
NO Check soldering.
Replace U203 if defective.
Check
RF 1'st SAW Filter
frequency & power.
Frequency = 1842.8 MHz?
Power -77dBm?
YES
NO
Check U206 soldering
Replace U206 if defective.
Check
RFLOVCO U206 pin 23,24
frequency & power.
Frequency = 1842.7 MHz?
Power -30dBm?
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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