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SLM-7650 Satellite Modem
Maintenance
5.2.5
Fault/Alarm Analysis
This section describes the possible problems and trouble shooting actions for the each of
the faults listed in the Fault Tree (Table 5-1).
Note: Have the modem configuration and fault information available when contacting
5.2.5.1
Modulator Faults
Fault/Alarm
MODULE
IF SYNTHESIZER
DATA CLOCK SYN
I CHANNEL
Q CHANNEL
AGC LEVEL
Comtech EF Data Customer Support if on-site troubleshooting efforts fail to
determine the problem with the modem.
Table 5-2. Modulator Fault Information
Modulator section fault.
Typically indicates that the modulator will not program.
Return the modem for repair.
Modulator IF synthesizer fault.
This is considered a major alarm, and will turn off the modulator output.
Return the modem for repair.
Transmit data clock synthesizer fault.
This is considered a major alarm, and will turn off the modulator output.
This fault indicates that the internal clock VCO has not locked to the incoming data
clock, or the internal clock synthesizer has not locked to the internal reference.
Ensure the proper data rate has been set up and selected, and the incoming data rate
matches the modem selections.
Activity alarm for the I channel digital filter.
This alarm is considered a major alarm, and will turn off the modulator IF output.
An alarm in this position indicates either a fault in the scrambler, or if the scrambler is
disabled, the alarm indicates a loss of incoming data.
If the fault is active with the scrambler turned off, check for input data at the DATA I/O
connector. If data is present return the modem for repair.
Activity alarm for the Q channel digital filter.
Use the I channel procedure.
Output power AGC level fault.
Indicates the level at the modulator output is not the programmed level.
Return the modem for repair.
Possible Problem and Action
5–9
Revision 4
MN/SLM7650.IOM
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