Nautel NX15, Troubleshooting Manual

Page: 39 / 274

NX25/NX15 Troubleshooting Manual Responding to alarms
Issue 5.0 2016-05-06 Page 1-31
Rack #: High B+ Voltage If the B+ voltage is more than 10 V above the B+ voltage set point,
the rack interface will attempt to decrease the rectifier’s output. If
the rack interface reaches the bottom of its adjustment range and
the B+ voltage remains 10 V or more above the B+ voltage
setpoint for more than 15 seconds, this alarm will occur. The
alarm will clear when the B+ voltage changes to within 10 V of the
B+ voltage setpoint, or the B+ power supply is inhibited (by turning
RF Off, for example). If the alarm persists while the transmitter is
producing RF power, check the ac mains voltages and verify they
are within ±10% of the nominal voltage for which the transformer
is tapped. Verify the mains transformer is tapped correctly (see
“Installing the power transformer” on page 3-1 in the Installation
Manual). If the alarm persists, replace the rectifier assembly (see
“SCR Rectifier Inspection/Replacement” on page 1-66 ) or the rack
interface PWB (see “Rack Interface PWB replacement” on
page 1-64 ).
Rack #: High Rectifier
Temperature This alarm indicates that the rectifier heatsink temperature has
exceeded 100 degrees Celsius. The exciter should reduce the
transmitter’s output power before this alarm occurs (see “Exciter:
High Temperature Foldback” alarm). The alarm will clear once the
rectifier heatsink temperature drops below 99.5 degrees Celsius.
The alarm indicates that there is excessive dissipation in the
rectifier, likely due to high current draw. This may be due to the
secondary voltage of the power transformer being lower than
specified. Verify the mains transformer is tapped correctly (see
“Installing the power transformer” on page 3-1 in the Installation
Manual). If the alarm persists, replace the rectifier assembly (see
“SCR Rectifier Inspection/Replacement” on page 1-66 ).
Rack #: Low AC Voltage This alarm indicates the rack interface’s Ac Sample meter is
below 256 V. The alarm clears when the sample rises above this
voltage. It is caused by an improperly tapped transformer, or a
transient on the ac mains. Verify the mains transformer is tapped
correctly (see
“Installing the power transformer” on page 3-1 in the
Installation Manual). If so, monitor the ac mains for transient
conditions when this alarm occurs. See
“Rack #: Low AC” on
page 1-44 .
Alarm (with Prefix) Description and Troubleshooting Action