Troubleshooting Manual

VX150 TO VX2 TROUBLESHOOTING MANUAL RESPONDING TO ALARMS
PAGE 3.1.12 VERSION 0.1 2020-12-01
No External 10 MHz This alarm occurs if frequency locking to an external 10 MHz source is enabled and no
external 10 MHz is detected. The exciter will automatically switch over to the internal
10 MHz reference, and will continue to run. Check the 10 MHz input. If there are no
problems with the 10 MHz signal and connection, suspect the Exciter/Control PWB (A1).
No LAN Connection This alarm occurs if the transmitter is not detecting communication over the LAN connection.
This alarm is typically only visible in the Events Log, since it will not be transmitted when
communication is interrupted.
No One Pulse per Second This alarm occurs if the pilot phase locking to 1 PPS is enabled and the 1 PPS signal is not
present. Check the 1 PPS input. If there are no problems with the 1 PPS signal and
connection, suspect the Exciter/Control PWB (A1).The transmitter takes no action on this
alarm
Overall Summary Not displayed in AUI or UI status. Configurable as a remote output.This alarms occurs if there
are any alarms present. Check for associated alarms, and follow the associated
troubleshooting procedure, if present.
PA Fail Foldback This alarm occurs if the control system determines that the calculated dissipation in any FET
on a PA is above the high dissipation threshold (?? W), or the forward power being asked for
out of an individual PA [calculated as (output power - combiner losses) / number of active
PAs in the system] is above the PA output high threshold (400 W)(850 W for VS2.5 or 900 W
for VS3). The forward power of the transmitter will be limited to a level such that neither of
these thresholds are exceeded. Check for associated alarms. Typically, the assertion of this
alarm is the result of a PA failure or removal, or a high SWR condition. If no other alarms are
being indicated, contact Nautel for further support
PA Fail/PA1 Fail This alarm occurs if the dc input current for the PA (A7), also PA1 for VX1.5/VX2 transmitters)
has fallen below a predetermined threshold (typically less than 50% of the average PA
current of the operational PAs, or below 500 mA, whichever is lower). This may be caused by
a cabling fault on the PA, loss of PA voltage or bias, or a defective FET. The transmitter's
output power will be reduced (see Table 1.3 on page 1-31) and this condition could cause Per
PA Foldback and Reject Foldback alarms. Perform the “PA resistance checks” on page 1-37.
If there is no problem found with the PA, or the alarm still persists after replacing the PA,
suspect the PS Distribution PWB (A2).
PA2 Fail For VX1.5/VX2 transmitters only. This alarm occurs if the dc input current for PA2 (A8) has
fallen below a predetermined threshold (typically less than 50% of the average PA current of
the operational PAs, or below 500 mA, whichever is lower). This may be caused by a cabling
fault on the PA, loss of PA voltage or bias, or a defective FET. The transmitter's output power
will be reduced (see Table 1.3 on page 1-31) and this condition could cause Per PA Foldback
and Reject Foldback alarms. Perform the “PA resistance checks” on page 1-37. If there is no
problem found with the PA, or the alarm still persists after replacing the PA, suspect the PS
Distribution PWB (A2).
Alarm Name Description and Troubleshooting Action