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MAINTENANCE
WJ-8718-19/FE HF RECEIVER
4.3.4.18
FM/CW/SSB Detector, A4A9, (791599) Testing and Troubleshooting
FM/CW/SSB Detector Testing and Troubleshooting includes a CW/SSB
Detector Checkout procedure, an FM Detector Checkout Procedure and fault isolation
information.
A Signal Generator, RF Voltmeter and an Oscilloscope
(Table 4-1) are
required to perform the tests outlined below.
4.3.4.18.1
CW/SSB Detector Checkout Procedure
Perform the following procedure in the sequence given.
If any specified
result is not obtained, refer to Table 4-17 for fault isolation.
1.
Deenergize the receiver.
2.
Remove PC board A4A7.
Place PC board A4A9 on an
extender.
3.
Connect the Oscilloscope Vertical Input to A4XA9
pin 57 using a short coaxial cable with clip leads on
one end.
Connect cable shield to the IF Motherboard
j
ground plane.
4.
Connect the Signal Generator RF output to A4XA9
pin 13 using a short coaxial cable with clip leads on
one end.
Connect cable shield to the ground plane.
Terminate the generator with a 50 ohm load.
Set the
!
Generator output frequency to 455.4 MHz and output
i
level to -33 dBm.
5.
Energize the receiver and select the USB Mode.
The
i
Oscilloscope should display a level of 0.5 V p-p at
400 Hz.
The waveform should be a clean sine save.
8.
If the signal in step 5 is incorrect, check the test
;
points given in Table 4-17 with an RF Voltmeter and
high impedance probe. When a faulty signal is
encountered, replace the key components indicated and
repeat
the Checkout
Procedure.
Figure 6-20,
FM/CW/SSB Detector Schematic Diagram should be
referred to if additional signal tracing/fault isolation is
necessary.
9.
When the Input Converter has been repaired and is
operating satisfactorily, deenergize the receiver and
disconnect test equipment, if no further tests are to be
performed.
4.3.4.18.2
FM Detector Checkout Procedure
Perform the following procedure in the sequence given. If any specified
result is not obtained, refer to Table 4-17 for fault isolation.
4-36
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