Nautel VS1, Troubleshooting Manual, Page: 29 / 109

VS1 Troubleshooting Manual Responding to alarms
Issue 10.0 2018-10-29 Page 1-21
PA Pwr
Foldback
Output Network
(amber)
This alarm occurs if the control system determines that the
calculated dissipation in any FET on a PA is above the high
dissipation threshold (170 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). 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 Volts Fail PS (red) This alarm is for indication only, and occurs when the voltage
output by the power supply module does not match what the
controller thinks it should be based on the control signal it is
sending to the power supply module. No action is taken on this
alarm. This alarm may show up when turning RF on or off.
Pilot Unsync Exciter (amber) This alarm occurs if there is no synchronization between the
10 MHz and 1PPS signals. It may indicate that the GPS receiver
is not detecting a signal. Check the GPS receiver and
antenna.The VS1 takes no action on this alarm.
PLL Unlock Exciter (red) This alarm indicates that the exciter’s master clock is not locked.
Possible causes are an out-of-range 10 MHz input or a hardware
failure on the exciter/control PWB (A1). The VS1’s RF output is
inhibited.
Preamp Fail PA (red) This alarm occurs if the
IPA Output Low
alarm is present and the
measured pre-amp current is below 17.5 mA. The VS1 takes no
action on this alarm. See
IPA Output Low
for troubleshooting
tips.
PS A AC Fail PS (red) This alarm occurs if the power supply module (U2) is reporting an
ac failure, indicating its ac input voltage is less than 175 V ac. The
VS1 will inhibit its RF output until the alarm is cleared. Check the
ac voltage applied to the power supply module. If the ac voltage is
acceptable, try replacing the power supply module with a new
module (see “Power Supply Module Replacement” on page 1-39 ).
Alarm Name
AUI and
(Front Panel)
Front Panel
LED (color)
Description and Troubleshooting Action