Nautel XR12 Troubleshooting Manual

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

Contents

XR12 Troubleshooting Manual Responding to alarmsIssue 3.0 2009-07-28 Page 1-191. If E19 is between pins 2 and 3, verify the dc voltage between TB2-6 and ground on theremote interface PWB is approximately 24 V. This signifies there is no external PDM inhibitcommand.2. If E19 is between pins 1 and 2, verify the dc voltage between TB1-3 and TB2-6 on theremote interface PWB is 0 V. This signifies there is no external PDM inhibit command.3. If the conditions in Step 1 and Step 2 are met, suspect the remote interface PWB or thecontrol/display PWB.Int. serial failThis alarm indicates that there is no communication with the remote interface PWB. This alarm istriggered if two seconds go by without acknowledgement from the remote interface PWB of thecontrol/display PWB's request for information. (The control/display PWB requests updates fromthe remote interface PWB every 200 ms).1. Check the cable between connector P1 (mates with J1 of the control/display PWB) andconnector P15 (mates with J13 of the remote interface PWB). If the cable and connectionsare intact, suspect a problem with the control/dispaly PWB or remote interface PWB.Mod. protectionThis fail is reported from the remote interface PWB.The exciter monitors a sample of the RF output and conditions the modulator outputs if the RF drivecurrent becomes great enough to damage the modulators. A Mod Protection alarm may occur fromoverdriving the transmitter (high output power, high modulation depth, or very low modulatingfrequency), a fault in the control/display PWB's alarm circuitry, or a fault in the remote interfacePWB's circuitry. Troubleshoot a Mod Protection alarm as follows:1. Examine the operating conditions under which the alarm occurred. A Mod Protectionalarm may be initiated if the transmitter is running at rated power with high modulation at alow modulating frequency. If these conditions were present at the time of the alarm, adjustthe modulating audio low frequency roll off to 30 Hz.2. Use an oscilloscope to view TP6 on the interphase PDM driver PWB. If the transmitter isoperating at rated power and the audio is clipped (see Figure 1.3), complete “ModulationPeak Limiting” on page 5-5 of the XR12 Operating and Maintenance Manual.