Nautel NX15, Troubleshooting Manual

Page: 56 / 274

NX25/NX15 Troubleshooting Manual Responding to alarms
Page 1-48 Issue 5.0 2016-05-06
Troubleshooting RF power modules
Maintenance philosophy
Recommended troubleshooting procedures for RF power modules are limited to “go” or “no-go”
resistance or diode measurements on the module’s power semi-conductors and replacement
procedures for these devices.
Special Tools and Test Equipment
The following test equipment and cables are required to troubleshoot an RF power module.
• A digital multimeter with resistance and diode settings.
• A torque screwdriver with a torque range of 0.0 to 2.26 N-m (0 - 20 in.-lbs). Required for
installing MOSFET attaching hardware.
• A soldering iron and desoldering tool.
• An NX25/NX15 spares kit (contains replacement semi-conductors).
Electrostatic Precautions
The RF power module contains semiconductor devices that are susceptible to damage from
electrostatic discharge. Be sure to follow the electrostatic precautions in
“Electrostatic protection” on
page 1-3 at all times.
Preparation for Troubleshooting
1. Follow the procedure in “Removing an RF power module” on page 1-45 to remove the RF
power module from the transmitter.
2. Place the RF power module on a suitable work surface.
3. Perform the resistance measurements on the modulator and power amplifier MOSFETs as
described in “Resistance measurements” on page 1-49 .
4. Perform the diode checks on the free-wheel diodes as described in “Power Amplifier FET
replacement” on page 1-51