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SLM-7650 Satellite Modem
Maintenance
5.2
Fault Isolation
The fault monitoring and internal test modes of the modem assists the operator in
determining if the link problem is the result of a faulty modem. The maintenance
philosophy of the SLM-7650 identifies the modem is the LRU. If the modem is found to
be faulty, remove the modem from the rack and return to the depot for repair.
The fault isolation procedure lists the following categories of faults or alarms.
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5.2.1
Fan
A six-month fan inspection is suggested. Listen for uncommon fan noise and check that
air is flowing out of the back of the modem.
5.2.2
M & C Battery
There is a small battery in the monitor and control section that may need to be replaced
every 5 years. Schedule periodic replacement every four years or if a battery low alarm
occurs while the modem has been plugged in. The battery part number is BTM4T28-
BR12SH. The Comtech EF Data part number is HW/M4T28.
The battery fits on a surface mount integrated chip that functions as a timekeeper and
memory device. The battery voltage is checked upon power up and, automatically, every
24 hours as long as the device is powered up. A battery low alarm will be generated if
the voltage falls below 2.5 Vdc. The modem configuration should be checked if the
battery low alarm occurs on power up because the data integrity may be compromised if
the battery voltage falls below 2.5 Vdc.
A fresh battery should be installed if the battery alarm is generated during the 24-hour
interval check. This indicates that the battery is near end of life. The modem
configuration has not been compromised, since the modem has been constantly powered
up.
5.2.3
Faults/Alarms
System faults are reported in the "Faults/Alarms" menu, and stored faults are reported in
the "Stored Flts/Alms" menu. To determine the appropriate action for repairing the
modem, refer to Table 5-1 and the list of possible problems.
Modulator
Demodulator
Transmit Interface
Receive Interface
Common Equipment
5–4
Revision 4
MN/SLM7650.IOM
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