Comtech EF Data SDM-9000 - Manual (Page 177)

SDM-9000 Satellite Modem Maintenance
Rev. 4 6–19
6.2.2.2 Fault/Alarm Analysis
6.2.2.2.1 Modulator Faults
Fault/Alarm Possible Problem and Action
IF SYNTHESIZER Modulator IF synthesizer is faulted.
This is considered a major fault and will turn off the modulator
output. Return the modulator module for repair.
DATA CLOCK ACT Transmit data clock activity alarm.
This fault is not considered a major fault and will not turn off the
modulator output. The problem is most likely on the interface
card or external to the modem. Use the baseband loopback and
interface loopback test modes for checking the interface. Ensure
the incoming data clock is present at the modem DATA I/O
connector. If data and clock are present at the DATA I/O, then
replace the interface card to clear the alarm and return the card
for repair.
DATA CLOCK SYN Transmit data clock synthesizer fault.
This fault is an indication 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. This is
considered a major fault and will turn off the modulator output.
Ensure the proper data rate has been set up and selected, and
the incoming data rate matches the modem selections.
I CHANNEL Activity fault for the I channel digital filter.
This alarm is considered a major fault 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, it 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, replace the interface card to clear the fault and return
the interface card for repair. If the fault is active with the
scrambler turned on, replace the modulator card and return it for
repair.
Q CHANNEL Activity fault for the Q channel digital filter. Use the I channel
procedure above.
AGC LEVEL Output power AGC level fault.
Indicates the level at the modulator output is not the programmed
level. Replace the modulator card and return it for repair.
INTERNAL SCT SYN Internal TX data clock synthesizer fault.
The SCT has failed to lock to the internal reference. Replace
modulator board.
EXT REF ACT External reference activity alarm.
Activity alarm for the external reference clock. Indicates clock
reference not detected.