VK Corporation VG207, Service Manual

Page: 35 / 70

5.14 RX Sensitivity Trouble (E-GSM)
START
Check
RF connetor U100 pin 1
frequency & power.
Frequency = 947.4 MHz
Power
≥
-72dBm
Check
RF 1'st SAW Filter BPF5 pin3
frequency & power.
Frequency = 947.4MHz
Power
≥
-77dBm
Check
ANT Switch U102 pin 10
frequency & power.
Frequency = 947.4MHz
Power ≥ -72dBm
Check U101 soldering and short.
Replace U101 if defective.
Check :
• U102 soldering
• U102 pin 10 Low voltage
• U102 pin 7 Low voltage
Replace U102 if defective.
Check BPF5 soldering.
Replace BPF5 if defective.
NO
YES
YES
YES
NO
NO
Check
RF Mainchip U203 pin 27
frequency & power.
Freuency = 947.4MHz
Power
≥
-60dBm
Set
• Phone : Test mode
62CH, 7level (TCH)
62CH, -60dBm (BCCH)
• Spectrum analyzer as shown in Remarks.
• Oscilloscope as shown in Remarks.
Check U203 soldering.
Replace U203 if defective.
NO
Remarks
1. Call connection : TEM3 execution
ti Enter
tms 1 Enter
txpw 1 7 Enter
rfe 7 Enter
2. 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
3. Oscilloscope : 500mV/div, 2ms/div
4. RF Cable Loss : about 10dB