CDR-3250/80 TECHNICAL MANUAL
Issue 2.2
5-5
18.
Tune receiver to 11.251 MHz and check for
LSB audio (/DET AUDIO) signal.
19.
Set bite control to produce a test
frequency of 0.750 MHz and set gain to 6
dB above threshold.
20.
Tune receiver to 17.249 MHz and check for
USB audio (/DET AUDIO) signal.
21.
Set bite control to produce a test
frequency of 0.750 MHz and set gain to 6
dB above threshold.
22.
Tune receiver to 27.751 MHz and check for
LSB audio (/DET AUDIO) signal.
5-5.2.3
BIT.
During normal receiver operation, fault
detectors are operating in the background. Table 5-1 lists
the fault detectors, their locations and the fault signal sent
to the Control section in the Digital module. If a fault is
detected, the Control section stores the information in
memory, causes the fault indication to be shown on the
display, and sends the fault information over the remote
control bus. The operator can view the current or
cumulative faults (since power up) using the UTILITY
FAULTS soft key menu.
5-5.3
Troubleshooting Procedure.
Equipment
troubleshooting should be performed in the following
order:
1. Fault identification.
2. Initial checks.
3. Front panel display interpretation.
4. Signal tracing (If required).
5. Subassembly replacement.
5-5.3.1
Fault Identification.
A fault is usually indicated
by a fault indication on the front panel display, the bus
controller detecting a fault bit, or by the receiver not
detecting a known good signal.
5-5.3.2
Initial Checks.
Before detailed troubleshooting,
perform the following:
1. Check that the display on the front panel is on,
and the power/volume knob is on. If the front
panel display is off, and the power/volume knob
is set to on, ensure that input power is correct.
NOTE
Display may not be visible in
bright ambient light if 5%
intensity is selected.
2. Check that valid frequency, bandwidth, and other
parameters are correctly set.
3. Check for correct external reference frequency. If
an external reference frequency is used, try
disconnecting it, and recheck the receiver.
4. Check operation in both LOCAL and REMOTE.
5-5.3.3
Front Panel Display Interpretation.
Further
isolation is done by using the front panel to view the
present or cumulative faults. To view the fault from the
Primary soft key menu select
NEXT, NEXT, NEXT
to
display the Utility soft key menu. Refer to paragraph 3-
7.5.3 for further operation. Table 5-2 lists all fault
messages, their meaning, and the maintenance action to
take.
5-5.3.4
Signal Tracing.
If the failed subassembly cannot
be isolated using the initial check or front panel display
interpretation, isolate the failed subassembly using
conventional signal tracing techniques. Refer to chapter 4
and figure 5-1 for signal flow descriptions.
Signals are checked at various locations in the equipment
using an RF signal generator and oscilloscope (see figures
FO-2 through FO-5). Tables 2-1 through 2-5 lists signals at
the rear panel connectors.
Table 5-1 Fault Detectors
Detector
Module Location
Fault Signal
Power Supply
Power Supply
PS FAULT
1st LO Driver
RF Analog
RF FAULT
3rd LO
RF Analog
RF FAULT
Output Loop PLL
Synthesizer
OUTPUT/FINE FAULT
Fine Loop PLL
Synthesizer
OUTPUT/FINE FAULT
Step Loop PLL
Synthesizer
STEP FAULT
Table 5-2 Front Panel Fault Messages.
Courtesy of http://BlackRadios.terryo.org
