Nautel NX15, Troubleshooting Manual

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NX25/NX15 Troubleshooting Manual Detailed Circuit Descriptions
Issue 5.0 2016-05-06 Page 2-15
During normal operation the RF shorting relay is in an open state. U22 sends out a 5 V pulse for
50 ms to the gate of Q4. This allows Q4 to conduct current through the ‘release’ coil causing the RF
shorting relay to open its contacts. After the 50 ms pulse the gate of Q4 will return to 0 V and Q4 will
stop conducting, the relay will remain latched in the open position. An RF Power Module #: RF Relay
Open status event is generated.
When the module is disabled or an internal alarm occurs, U22 disables the RF drive signal and then
closes the RF shorting relay by sending a 5 V 50 ms pulse to the gate of Q3. The shorting relay will be
latched into the closed position, allowing the module to be removed from the transmitter.
LED Indicator:
Bi-colour LED DS1 is visible from the front cover of the RF power module.
Microcontroller U22 controls the light colour of DS1 by allowing Q1, Q2, or both, to conduct. Refer
to the following colour codes to determine the status of the RF power module:
– green, solid: module is operating normally and producing RF power
– amber, off: module is RF off
– solid red: module has a non-latching alarm
– flashing red, then green: module is producing RF, but has an alarm
– long red, short amber: module has a latching alarm
– long red, short off: module has no valid serial number
– short red, long off: module has no valid serial address on the internal bus
– long amber, short green: module is producing RF, but no serial communications
– long amber, short red: module is not producing RF and no serial communications
Programming Header:
Connector J2 is a JTAG programming header used for initially
programming microcontroller U22. It is not used during normal operation.
MONITORING
Dc Current:
The Dc Current sample from the modulator output is monitored by microcontroller
U22 for diagnostic, telemetry and fault detecting purposes. The sample is monitored by two separate
sections of U22.
The analog average dc current sample is detected by ADC0 (pin 23) of U22. The dc current sample is
heavily filtered through R75 and C74, minimizing current sample variations due to modulation.