XIEGU
Product Maintenance Manual G90/G90S Portable Short-Wave Transceiver
XIEGU All Rights Reserved Version No.: 1.0 2022-07 Page
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Fault phenomenon: The receiving IQ balance cannot be adjusted
Maintenance methods:
The instrument settings are as follows:
Name
Setting Parameters
Parameter 1
Parameter 2
Parameter
3
Signal Source
Frequency:
14.271MHz
Amplitude:
-40dBm
/
Oscilloscope
Time base: 1ms
Y-axis:
100mV
X10 gear
After PRE is turned on, the measured data at each checkpoint shall be
as follows:
Checkpoint
Frequency
Amplitude
mVpp
Name
A16
1kHz
350
Baseband
signal of
circuit I
A17
1kHz
350
Baseband
signal of
circuit Q
If the amplitude difference between the two checkpoints exceeds 10mV,
it means that the baseband signal is unbalanced, and further inspection
is required as follows:
Fault
Phenomenon
Maintenance Method
Small signal board
Checkpoint
IQ is unbalanced
Baseband amplifier
unit
Whether there is any
false welding
Back capacitance part
Whether the
components are faultily
welded or defective
If the electrolytic capacitor on the back of the baseband amplifier
has individual defects, it will also cause IQ signal imbalance fault,
so it should be checked emphatically.
100 uF/ 16V chip tantalum capacitor is used for the old version of
the small signal board, which has a high damage rate, so special
attention should be paid during maintenance.
Baseband
amplifier
Back of baseband
amplifier
