Nautel XL12 Technical Instructions

Contents

12 000 WATT AM BROADCAST TRANSMITTERXL12Page 4-201 January 2002ELECTROSTATIC PROTECTION4.5 The transmitter's assemblies containsemiconductor devices that are susceptible todamage from electrostatic discharge. Prior toremoving an assembly from the transmitter, andwhile servicing an assembly, the followingprecautions must be observed:NOTEElectrostatic energy is produced when twoinsulating materials are rubbed together. Aperson wearing rubber-soled shoes, walkingacross a nylon carpet or a waxed floor, cangenerate an extremely large electrostatic charge.This effect is magnified during periods of lowhumidity. Components such as integratedcircuits, field-effect transistors, thyristors, andSchottky diodes may be damaged by this highvoltage unless adequate precautions are taken.4.5.1 PERSONAL DISCHARGING:Maintainers should be electrically discharged by asuitable grounding system (anti-static mats, groundingstraps) during removal of an assembly from thetransmitter and while handling the assembly formaintenance procedures.4.5.2 HANDLING/STORAGE: The assemblyshould be placed in an anti-static bag when it is notinstalled in a host transmitter or when it is not beingsubjected to maintenance procedures. Electroniccomponents should be stored in anti-static materials.4.5.3 TOOLS/TEST EQUIPMENT: Testingand maintenance equipment, including soldering andunsoldering tools, should be suitable for contact withstatic sensitive semiconductor devices.4.5.4 STRESS CURRENT PROTECTION:Every precaution should be taken to ensure the staticsensitive semiconductor devices are protected fromunnecessary stress current. This is achieved byensuring:- current is not flowing when an electricalconnection is broken.- voltages are not present on external control/monitoring circuits when they are connected.PRE-STARTUP CHECKS4.6 Prior to applying input power to thetransmitter, observe the following:(a) Verify all assemblies/modules are installed andmating connectors are fully engaged.(b) Verify the external input/output wiring isconnected as detailed in section 2.(c) Visually inspect the internal electrical wiringfor defects such as damaged insulation, brokenwires, wrong connections and/or looseconnections.(d) Verify all panels/covers are installed and theirattaching hardware is firmly secured.(e) Verify the transmitter's RF output is terminatedinto a 50 ohm load - an antenna that isinterfaced by an appropriate matching systemfor normal operation, or a 50 ohm resistivedummy load that is rated at 20 000 watts foradjustment and testing procedures.(f) Verify appropriate primary winding taps of thepower transformer have been selected tomatch the voltage of the input power source(refer to transmitter configuration sheet.)READING METERS4.7 The enabled/disabled status of the control/monitor panel's RF KILOWATTS, DC AMPERES andDC VOLTS meters is determined by the setting of theSTATUS CONTROL - METER ON/OFF switch. Theswitch's setting will toggle between one of two stateseach time it is pressed and released. When it is inthe meter enable (on) state, its integral lamp will beturned on and all three meters will be enabled.When it is in the meter disable (off) state, its integrallamp will be off and all three meters will be turnedoff.4.7.1 READING RF POWER METER: TheRF KILOWATTS meter displays forward power on theupper scale and reflected power on the lower scalewhen the meter has been enabled (integral lamp ofSTATUS CONTROL - METER ON/OFF switch is on).Parameter to be displayed is selected by pressing/releasing associated SELECT METER SCALE switch untilthe lamp associated with the desired input parameteris turned on.