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LBI-39128 MAINTENANCE
34
transmitter channels. Repeat steps 2 through 6 for each
transmitter channel until all are re-configured.
TROUBLESHOOTING
After you think you have fixed a transmitter alarm
problem, switch the transmitter off (12V power supply), then
back on. This will cause the next test call to be placed to that
transmitter and thereby speed up the check-out process and
the transmitter’s return to service.
Table 10 lists some of the possible causes and the
corresponding corrective action for various symptoms that
might be observed.
Table 10 - Troubleshooting Symptoms
SYMPTOM POSSIBLE CAUSE(S) CORRECTIVE ACTION
Constant antenna alarm for one antenna,
but antenna appears to be OK.
Lower (power) Alarm Limit is set too
high, Upper (power) Alarm Limit is set
too low, or Upper (SWR) Alarm Limit
is set too low.
Check and possibly re-configure the
alarm limit(s) (see the Parameters
heading in the Operation section).
Power sensor at antenna input needs
calibration or is defective.
Check and possibly re-calibrate the
power sensor (see the Power Sensor
Calibration heading in this section).
Cable from the power sensor to the
PMU (can be many cables and
connectors in series) is connected to the
wrong point or is defective.
Check the continuity of the cable from
the power sensor to the PMU (see the
interconnection diagrams at the end of
this manual).
PMU input circuit is defective. Apply a dc voltage (negative ground) to
the power sensor end of the cable to the
PMU (see Table 7 for the voltage to
represent the expected power). If the
alarm remains, the cable or the PMU
input is defective.
Occasional antenna alarm for one
antenna, but antenna appears to be OK.
Power sensor at antenna input needs
calibration or is defective.
Check and possibly re-calibrate the
power sensor (see the Power Sensor
Calibration heading in this section).
No antenna alarm is reported when the
cables between the power sensor and
the PMU are disconnected.
Lower Alarm Limit is set to zero. Re-configure the Lower Alarm Limit
parameter for the antenna to some non-
zero value (see the Parameters heading
in the Operation section).
(Continued)