Nautel NX15, Troubleshooting Manual

Page: 34 / 274

NX25/NX15 Troubleshooting Manual Responding to alarms
Page 1-26 Issue 5.0 2016-05-06
Module #: External
Disable Active This alarm indicates the PDM cable has been disconnected from
the front of the RF power module, which causes the power
module to be immediately disabled. If this alarm occurs, reconnect
the PDM drive cable associated with that RF power module. If the
problem persists, swap the affected RF power module with an
operational RF power module’s position. If the fault follows the RF
power module, replace the RF power module (see
“Removing and
reinstalling RF power modules” on page 1-45 ). If the fault remains
with the position, try replacing the PDM drive cable. If the alarm
persists, replace the source of the
PDM signal (see “PDM Drive
Distribution PWB replacement” on page 1-62 ).
Module #: High B+
Voltage This alarm indicates the RF power module's B+ meter has
exceeded
450 V . If high B+ voltage alarms are present for other
system components, see the troubleshooting action for those
alarms. If the alarm persists, replace the RF power module (see
“Removing and reinstalling RF power modules” on page 1-45 ).
Module #: High DC
Current This alarm indicates that the RF power module's DC Current
meter has exceeded 22 A, or the RF power module's peak DC
current has exceeded the threshold applied to the
microcontroller's comparator. This alarm will immediately disable
the RF power module, and latch it off. If this alarm occurred in
conjunction with an Overmodulation alarm, follow the
troubleshooting action for that alarm. Otherwise, try resetting the
alarms using the AUI. If the alarm persists, replace the RF power
module. If the alarm clears, troubleshoot the suspect RF power
module for RF FET failures (see
“Troubleshooting RF power
modules” on page 1-48 ). If the alarm persists, suspect that the
associated RF relay is not opening, or the associated gas
discharge tube has activated.
Module #: High PA
Voltage This alarm occurs because of one of two conditions: (1) the PA
voltage is at least 10% above the product of the B+ level and the
PDM duty cycle; or (2) the PA voltage has exceeded 95% of the
B+ value for more than 50 ms. The alarm is latching and will
cause the associated RF power module to disable itself. This
alarm generally indicates that a modulator FET has failed. See
“Troubleshooting RF power modules” on page 1-48 to determine
whether to replace the affected RF power module or to repair
damaged parts.
Alarm (with Prefix) Description and Troubleshooting Action