Nautel XR12 Troubleshooting Manual

Also see for XR12: Installation manual Operation and maintenance manual Preinstallation manual

Contents

XR12 Troubleshooting Manual Responding to alarmsPage 1-16 Issue 3.0 2009-07-28This alarm indicates the PDM duty cycle of exciter B’s modulator drive is too high. Try to reset thealarm. If the alarm persists, proceed to the steps listed in “PDM drive fail”.PDM drive failThis fault indicates that the PDM drive is inoperative. If the exciter transfer function is set to auto,then the microcontroller will attempt an exciter changeover to the other side. If it cannot complete anexciter changeover, or if the exciter transfer function is set to manual, then this fault will cause ashutback.A PDM Drive Fail alarm indicates that the PDM drive signal’s duty cycle is too low (pulse width toonarrow). It may be caused by a fault on the interphase PDM driver PWB or the control display PWB'salarm circuitry. Troubleshoot a PDM Drive Fail alarm as follows:1. The PDM Drive Fail alarm initiates an automatic exciter changeover to the standby exciter.To troubleshoot a defective exciter circuit, set changeover to manual as detailed in “Changingautomation settings” in the Operating and Maintenance Manual.2. If the transmitter successfully switched to the standby exciter, suspect the main exciter'sinterphase PDM driver PWB.3. Use an oscilloscope to measure the voltage at TP6 on the interphase PDM driver PWB. Theindication should have a dc offset of 1.4 V ± 10%. If not suspect the remote interface PWBor the IBOC/DRM exciter if you are operating in all-digital (HD) mode.4. Measure the dc voltage at TP1 of the interphase PDM driver PWB. If the voltage is either0 V (and transmitter not shut back) or 15 V, suspect the control/display PWB.5. Use an oscilloscope to measure TP2 of the interphase PDM driver PWB. The signal shouldbe a square wave at the transmitter’s 2f PDM frequency (nominal 130 kHz). If not, suspect theRF synthesizer PWB.6. Measure the dc voltage at TP3 on the interphase PDM driver PWB. The voltage should bethe B+ voltage multipled by 0.02 ± 10%. If not, suspect the wiring to the B+ distributionPWB or the exciter interface PWB.7. If no faults were found in the previous steps, suspect the control/display PWB.