XIEGU
Product Maintenance Manual G90/G90S Portable Short-Wave Transceiver
XIEGU All Rights Reserved Version No.: 1.0 2022-07 Page
18
of
48
Fault phenomenon: BPF unit test fault (there is no amplitude-frequency curve in network
analysis test)
Maintenance methods:
1. First check the band switching control area on the back of the small
signal board:
Fault
Phenomenon
Maintenance Method
Small signal board
Checking
Area
No BPF
Whether there is false welding in the
switching control area
A8
2. Set the instrument:
Name
Setting Parameters
Parameter 1
Parameter 2
Parameter 3
Signal Source
Frequency:
14.271MHz
Amplitude:
-20dBm
/
Oscilloscope
Time base: 50ns
Y-axis:
100mV
X10 gear
Then check whether the signal amplitude of checkpoints A3, A6, A7,
A4 is normal in turn.
Area A6 collects the input of each segment of BPF;
Area A7 collects the output of each segment of BPF;
When PRE is turned on, the measured data at each checkpoint shall be
as follows:
Checkpoint
Frequency
MHz
Amplitude
mVpp
Name
A3
14.271
80
A6
14.271
80
Input of each segment
of BPF
A7
14.271
50
Output of each segment
of BPF
A4
14.271
380
Receive mixer input
3. After selecting a certain segment of BPF, the positive pressure
differential between the input and output switching diodes of this
segment of BPF shall be about 0.7 ~ 0.9V. If the selected BPF
switching diode has a reverse pressure differential, it indicates that the
gating of this segment is faulty.
4. The fault point of BPF unit can be found out according to the above
steps.
The damaged inductance and capacitance in BPF will also cause
faults, so pay attention to that.
