Nautel NX15, Troubleshooting Manual

Page: 40 / 274

NX25/NX15 Troubleshooting Manual Responding to alarms
Page 1-32 Issue 5.0 2016-05-06
Rack #: Low B+ Voltage If the B+ voltage falls to more than 15% below the B+ voltage set
point, the rack interface will attempt to turn up the rectifier output
voltage. If the rack interface reaches the top of its adjustment
range and the B+ voltage remains 25% or more below the B+
voltage setpoint for more than two (2) seconds, this alarm will
occur. The alarm will clear when the B+ voltage changes to within
25% 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 main B+ fuse and
replace as necessary. If the fuse is OK or the alarm persists,
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 #: Power Module #
Not Responding This alarm indicates that the rack interface PWB is not receiving a
response from the associated RF power module. Try swapping
the affected RF power module with an RF power module in
another location. If the alarm follows the RF power module,
replace the RF power module
(see “Removing and reinstalling RF
power modules” on page 1-45 ).
Rack #: Rectifier Fan 1
(or 2) Fail This alarm occurs if the speed of one of the SCR rectifier’s cooling
fans is below 3000 RPM for longer than 15 seconds. Inspect the
affected fan and, if necessary, replace it (see
“SCR Rectifier
Inspection/Replacement” on page 1-66 ).
Rack #: +15 V Fail This alarm occurs if the +15 V rail is outside the acceptable range
(12 V to 18 V). Disconnect the DC output of both +15 V power
supplies, and measure the voltage of each. If the output voltage of
either power supply measures outside of the acceptable range,
replace the affected power supply. If both power supplies measure
within the acceptable range, replace the rack interface PWB (see
“Rack Interface PWB replacement” on page 1-64 ).
Alarm (with Prefix) Description and Troubleshooting Action