Nautel XR12 Troubleshooting Manual

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

Contents

XR12 Troubleshooting Manual Detailed Circuit DescriptionsPage 2-18 Issue 3.0 2009-07-28fan power supply PWB (48 V) (NAPS30/01)See electrical schematic Figure SD-28.The fan power supply PWB is a switch mode power supply that converts the transmitter's B+ voltageto the dc voltage (48 V) used by the cooling fans.High voltage inputThe high voltage dc (B+) input (J3-1 and J3-2) is applied across varistors RV1 through RV3, whichprovide protection from high voltage transients. AC IND lamp DS1 provides a status indication of theinput voltage.Switching signalIC U3 is a high current FET driver that provides a switching PWM signal (0-18 V) to the primary oftransformer T2. The secondaries of T2 control the on/off status of FETs Q1 and Q2, which in turnswitch the transmitter’s B+ voltage to the primary of transformer T1.Output dc voltageThe secondary of step-up transformer T1 is rectified by diodes CR9 and CR10. This voltage isapplied through chokes L2 and L4 as the dc output (J4-1). A sample of the dc output voltage(resistors R5 and R9 and V OUT potentiometer R10) and current (transformer T3 and associatedcomponents) are applied to inputs of current mode PWM controller U8, which provides PWMswitching information to regulate the dc output voltage. V OUT potentiometer R10 provides a meansto adjust the attenuated voltage applied to U8, thereby adjusting the level of the dc output voltage.InhibitWhen a power supply fault occurs, an inhibit signal (0 V) is provided to J1-7. Opto-coupler U7 turnsoff and inhibits the dc output voltage via U8.