XIEGU G90, Maintenance Manual

Page: 23 / 48

XIEGU Product Maintenance Manual G90/G90S Portable Short-Wave Transceiver
XIEGU All Rights Reserved Version No.: 1.0 2022-07 Page
23
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48

Fault phenomenon: IQ output amplitude is unbalanced (ellipse or a line is displayed)
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:
The working voltage of IQ amplifier should be: 5V
Checkpoint Frequency
Amplitude
mVpp
Name
PIN1 1kHz 350
Baseband
signal of
circuit I
PIN7 1kHz 350
Baseband
signal of
circuit Q
A18 1kHz 350 Q signal
A19 1kHz 350 I signal

If the signal amplitude of a certain circuit is obviously small, it
indicates that there is a fault in the circuit, which should be
checked emphatically.

The coupling capacitor on the back of the small signal board
should also be checked to see whether the components are faultily
welded or defective

The 3.5mm stereo socket of IQ signal output should be checked
to see whether there is a short circuit or open circuit.
IQ Output amplifier
Output socket
Coupling
capacitor