Broadcast Electronics AM-2.5E, AM-5E User Manual

Page 1

WARNING

OPERATING HAZARDS

READ THIS SHEET AND OBSERVE ALL SAFETY PRECAUTIONS

ALL PERSONS WHO WORK WITH OR ARE EXPOSED TO POWER TRANSISTORS MUST TAKE PRECAUTIONS TO PROTECT THEMSELVES AGAINST POSSIBLE SERIOUS BODILY INJURY. EXERCISE EXTREME CARE AROUND SUCH PRODUCTS. UNINFORMED OR CARELESS OPERATION OF THESE DEVICES CAN RESULT IN POOR PERFORMANCE, DAMAGE TO THE DEVICE OR PROPERTY, SERIOUS BODILY INJURY, AND POSSIBLY DEATH.

DANGEROUS HAZARDS EXIST IN THE OPERATION OF POWER TRANSISTORS The operation of power tubes and power transistors involves one or more of the following hazards, any one of which,

in the absence of safe operating practices and precautions, could result in serious harm to personnel.

A. HIGH VOLTAGE – Normal operating voltages can be deadly. Additional information follows. B. RF RADIATION – Exposure to RF radiation may cause serious bodily injury possibly resulting in

blindness or death. Cardiac pacemakers may be affected. Additional information follows.

C. BERYLLIUM – OXIDE POISONING – Dust or fumes from BeO ceramics used as thermal links with

power transistors are highly toxic and can cause serious injury or death. Additional information follows.

D. HOT SURFACES – Surfaces of air–cooled heat sinks radiators can reach temperatures of 100 degrees

centigrade and cause burns if touched. Additional information follows.

E. RF BURNS – Circuit boards with RF power transistors contain high RF potentials. Do not operate an RF

power module with the cover removed. HIGH VOLTAGE The transmitter operates at voltages high enough to kill through electrocution. Personnel should always break the

primary circuits when access to the transmitter is required. RADIO FREQUENCY RADIATION Exposure of personnel to RF radiation should be minimized, personnel should not be permitted in the vicinity of open

energized RF generating circuits, or RF transmission systems (waveguides, cables, connectors, etc.), or energized antennas. It is generally accepted that exposure to “high levels” of radiation can result in severe bodily injury including blindness. Cardiac pacemakers may be affected.

The effect of prolonged exposure to “low level” RF radiation continues to be a subject of investigation and controversy. It is generally agreed that prolonged exposure of personnel to RF radiation should be limited to an absolute minimum. It is also generally agreed that exposure should be reduced in working areas where personnel heat load is above normal. A 10 mW/cm cies including the Occupational Safety and Health Administration (OSHA) as the standard protection guide for employee work environments. An even stricter standard is recommended by the American National Standards Institute which recommends a 1.0 mW/cm standard employee protection guide (ANSI C95.1–1982).

RF energy must be contained properly by shielding and transmission lines. All input and output RF connections, such as cables, flanges and gaskets must be RF leakproof. Never operate a power tube without a properly matched RF energy absorbing load attached. Never look into or expose any part of the body to an antenna, open RF generating circuit, or RF transmission system while energized. Monitor the tube and RF system for RF radiation leakage at regular intervals and after servicing.

DANGER –– BERYLLIUM OXIDE CERAMICS (BeO) – AVOID BREATHING DUST OR FUMES BeO ceramic material is used as a thermal link to carry heat from a transistor to the heat sink. Do not perform any

operation on any BeO ceramic which might produce dust or fumes, such as grinding, grit blasting, or acid cleaning. Beryllium oxide dust or fumes are highly toxic and breathing them can result in serious personal injury or death. BeO ceramics must be disposed of only in a manner prescribed by the device manufacturer.

HOT SURFACES Heat sinks and reject loads are air–cooled or conduction–cooled. The air–cooled external surface can operate at a

high temperature (up to 100° C). All hot surfaces may remain hot for an extended time after the transmitter is operated to off. To prevent serious burns, take care to prevent and avoid any bodily contact with these surfaces both during and for a reasonable cooling down period after operation.

per one tenth hour average level has been adopted by several U.S. Government agen-

per one tenth hour average level exposure between 30 Hz and 300 MHz as the

Page 2

BROADCAST ELECTRONICS, INC.

TRANSMITTER WARRANTY VOID NOTICE

THE PRODUCT WARRANTY WILL BE VOID IF THE TRANSMITTER IS INSTALLED AT A SITE WITH INADEQUATE LIGHTNING PROTECTION AND A DEFECTIVE TRANSMISSION LINE SYSTEM.

The transmitter is covered by a two year limited product warranty from Broadcast Elec tronics. However, the transmitter must be properly installed at a site with adequate lightning protection and transmission line systems. TO ENSURE THE TRANSMIT TER WARRANTY IS VALID, the transmitter must be installed: 1) as described by the INSTALLATION procedures presented in SECTION II of this manual, 2) at a transmitter site with a lightning protection system described in TRANSMITTER SITE LIGHTNING PROTECTION SYSTEM CHECKOUT (refer to SECTION II of this manual), and 3) at a transmitter site with a transmission line system described in TRANSMISSION LINE AND ANTENNA CHECKOUT (refer to SECTION II of this manual). FAILURE TO

PROPERLY INSTALL THE TRANSMITTER, PROVIDE AN ADEQUATE LIGHT NING PROTECTION SYSTEM, OR PROVIDE AN ADEQUATE TRANSMISSION LINE SYSTEM WILL VOID THE WARRANTY ON THE TRANSMITTER. If any

questions develop concerning the transmitter warranty and installation site systems, con tact the Broadcast Electronics Customer Service Department.

Page 3

BROADCAST ELECTRONICS, INC.

NOTICE TO THE EQUIPMENT USER

FCC Rule 73.1590 mandates the licensee of each AM station to make measurements for spurious and harmonic emissions to show compliance with the transmission system re quirements of Section 73.44 of the Commission's Rules. It is the broadcast station's respon sibility to ensure that the audio signal applied to a Broadcast Electronics E-Series AM transmitter conforms to the audio standard NRSC-1 (published as ANSI/EIA-549-1988). This is a mandatory requirement to ensure that the equipment complies to Section 73.44 and Section 73.128(C) of the Commission's Rules.

Page 4

WARNING

OPERATING HAZARDS

WARNING

The Broadcast Electronics AM transmitters contain high voltages and currents. If safety precautions are not practiced, contact with the high voltages and currents could cause serious injury or death. The trans mitter is equipped with many built-in safety features, however good judgement, care, and common sense must be practiced to prevent accidents.

In addition to high voltages and currents, the AM transmitters contain multiple circuit grounds with high ac and dc potentials with respect to the cabinet which is at earth potential. The potentials could cause serious injury or death if maintenance personnel simultaneously touch a circuit ground and the cabinet. As a result, operation of the transmitter with test equipment connected to transmitter output network, RF power module, RF combiner, or power supply components is extremely dangerous and must not be attempted. Therefore, never energize the transmitter with test equipment connected to the trans mitter output network, RF power module, RF combiner, or power supply components. Test equipment may be connected to the ECU circuit boards from the front of the transmitter using the supplied extender circuit board with power energized if required.

THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT GROUNDS WITH HIGH AC AND DC POTENTIALS WITH RESPECT TO THE CABINET WHICH IS AT EARTH PO TENTIAL. DO NOT ENERGIZE THE TRANSMITTER WITH TEST EQUIPMENT CONNECTED TO THE TRANSMITTER OUTPUT NETWORK, RF POWER MOD ULE, RF COMBINER, OR POWER SUPPLY COMPO NENTS.

Page 5

SCOPE OF MANUAL

This manual consists of two sections which provides the following information for the Broadcast Electronics AM-2.5E and AM-5E AM Broadcast Transmitters.

A. PART I - Contains information relative to installation, operation, and

maintenance applicable to the overall transmitter.

B. PART II - Contains detailed information for the following transmitter

modular units.

1. POWER SUPPLY ASSEMBLY

2. RF POWER MODULE

3. OUTPUT NETWORK

4. EXCITER/CONTROLLER UNIT (ECU)

PART I - TABLE OF CONTENTS

PARAGRAPH PAGE NO.

SECTION I GENERAL INFORMATION

1-1 INTRODUCTION 1-1 1-3 EQUIPMENT DESCRIPTION 1-1 1-4 GENERAL 1-1 1-6 EXCITER/CONTROL UNIT 1-1 1-12 OUTPUT NETWORK ASSEMBLY 1-4 1-13 RF POWER MODULE 1-4 1-15 POWER SUPPLY 1-4 1-16 COMBINER ASSEMBLY 1-4 1-17 TRANSMITTER CONFIGURATIONS 1-5 1-19 ACCESSORIES AND SPARE PARTS KITS 1-5 1-21 EQUIPMENT SPECIFICATIONS 1-5

SECTION II INSTALLATION

2-1 INTRODUCTION 2-1 2-3 UNPACKING 2-1 2-6 ENVIRONMENTAL REQUIREMENTS 2-1 2-8 COOLING AIR REQUIREMENTS 2-1 2-12 PRIMARY POWER 2-1 2-14 INSTALLATION 2-1 2-16 EQUIPMENT PLACEMENT 2-2 2-19 COMPONENT INSTALLATION 2-2 2-22 ECU CIRCUIT BOARDS 2-2 2-23 RF POWER MODULES 2-2 2-24 POWER SUPPLY 2-7 2-25 BATTERY INSTALLATION 2-8 2-26 CIRCUIT BOARD PROGRAMMING 2-8 2-28 EXCITER CIRCUIT BOARD 2-8 2-37 STEREO CIRCUIT BOARD 2-12 2-42 CONTROLLER CIRCUIT BOARD 2-12

 Broadcast Electronics 1999

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Page 6

PARAGRAPH PAGE NO.

2-55 POWER SUPPLY CIRCUIT BOARD 2-15 2-58 REMOTE CONTROL 2-16 2-59 GENERAL 2-16 2-84 WIRING 2-20 2-86 AUDIO INPUT CONNECTION 2-20 2-88 EXTERNAL STEREO RF INPUT 2-20 2-89 AM-2.5E/AM-5E RF TRANSMISSION 2-20

LINE CONNECTION 2-90 EXTERNAL INTERLOCK 2-20 2-91 MODULATION MONITOR 2-20 2-92 AC POWER CONNECTIONS 2-22 2-95 GROUND 2-22 2-96 TRANSMITTER SITE LIGHTNING PROTECTION 2-22

SYSTEM CHECKOUT 2-98 ANTENNA BALL-GAP LIGHTNING ARRESTOR 2-25 2-102 ANTENNA-TUNING-UNIT SPARK-GAP 2-25

LIGHTNING ARRESTOR 2-103 TRANSMITTER SITE GROUNDING SYSTEM 2-25 2-104 CABLE PROTECTION 2-26 2-110 ANTENNA RF FEED LINE 2-26 2-111 TRANSMISSION LINE AND ANTENNA CHECKOUT 2-26 2-113 ANTENNA VSWR 2-26 2-114 COAXIAL SWITCH CONTROLLER 2-26 2-115 ATU AND PHASOR CHECKOUT 2-28 2-116 INITIAL CHECKOUT 2-28 2-118 PRELIMINARY OPERATION AND ADJUSTMENT 2-28 2-120 TUNING 2-28 2-126 POWER LEVEL AND MODULATION MONITOR 2-29

CALIBRATION ADJUSTMENTS 2-138 STEREO ADJUSTMENT 2-30 2-149 SINGLE CHANNEL LEVEL 2-32

SECTION III OPERATION

3-1 INTRODUCTION 3-1 3-3 CONTROLS AND INDICATORS 3-1 3-5 OPERATION 3-12 3-6 TURN-ON 3-12 3-14 TURN OFF 3-13 3-16 METERING 3-13 3-17 FORWARD POWER 3-13 3-18 REFLECTED POWER 3-13 3-19 POWER ADJUST 3-13 3-21 MONO/STEREO OPERATION 3-14 3-23 STEREO OPERATION 3-14 3-24 MONO OPERATION 3-14 3-27 PILOT CONTROL 3-14 3-29 EXCITER MONITOR OPERATION 3-14 3-31 MONO/STEREO INDICATIONS 3-14 3-32 INPUT SELECTION 3-14 3-33 POLARITY SELECTION 3-15 3-34 X10 AUTORANGE INDICATIONS 3-15

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PARAGRAPH PAGE NO.

3-35 FAULT RESET 3-15 3-37 POWER SUPPLY FAULT RESET 3-15 3-39 OVER-CYCLE OFF 3-15 3-41 OVER-MODULATION PWM MUTE 3-15 3-43 TRANSMITTER MONITOR 3-15 3-45 BATTERY TEST 3-15 3-47 CONTROLLER PWM MUTE INDICATOR 3-16 3-49 CONTROLLER REMOTE FAIL-SAFE INDICATOR 3-16 3-51 EXCITER LOCK INDICATOR 3-16 3-53 EXCITER +5V/+15V/-15V INDICATORS 3-16 3-55 STEREO EQUALIZATION INDICATORS 3-16 3-57 RF POWER MODULE INDICATORS 3-16 3-59 POWER SUPPLY INDICATORS 3-16 3-61 EXCITER NEGATIVE LIMITER INDICATOR 3-16 3-63 HIGH/LOW AC LINE CONDITIONS 3-16

SECTION IV THEORY OF OPERATION

4-1 INTRODUCTION 4-1 4-5 FUNCTIONAL DESCRIPTION 4-1 4-6 ECU 4-1 4-7 GENERAL 4-1 4-8 STEREO CIRCUIT BOARD 4-1 4-11 EXCITER CIRCUIT BOARD 4-1 4-13 CONTROLLER CIRCUIT BOARD 4-2 4-18 POWER SUPPLY 4-2 4-19 RF POWER MODULE 4-2 4-24 RF COMBINER 4-7 4-27 OUTPUT NETWORK 4-7 4-31 POWER SUPPLY 4-8 4-34 POWER SUPPLY CIRCUIT BOARD 4-8 4-39 METERING 4-9 4-42 COOLING FANS 4-9 4-44 INTERFACE CIRCUIT BOARD (AM-5E ONLY) 4-9 4-46 DETAILED DESCRIPTION 4-9 4-47 POWER SUPPLIES 4-9 4-49 AC INPUT CIRCUITRY 4-9 4-53 ECU POWER SUPPLY ASSEMBLY 4-10 4-57 TRANSMITTER FLUSHING FANS 4-10 4-60 LOW-VOLTAGE POWER SUPPLY TRANSFORMER 4-10 4-62 POWER SUPPLY CIRCUIT BOARD 4-10 4-65 CONVENTIONAL RECTIFIER CIRCUITRY 4-13 4-68 SWITCHING POWER SUPPLY CIRCUIT 4-13 4-76 MODULATOR CIRCUIT BOARD 4-14 4-81 POWER AMPLIFIER CIRCUIT BOARDS 4-15 4-86 SEQUENCE OF OPERATION 4-15 4-91 RF CIRCUITRY 4-16 4-92 EXCITER CIRCUIT BOARD 4-16 4-98 STEREO CIRCUIT BOARD 4-17 4-102 RF POWER MODULE 4-17 4-109 RF COMBINER 4-21 4-110 HARMONIC BAND-PASS FILTER 4-22

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PARAGRAPH PAGE NO.

4-111 DIRECTIONAL COUPLER CIRCUIT BOARD 4-22 4-115 T-MATCHING NETWORK 4-22 4-116 LIGHTNING PROTECTION CIRCUIT BOARD 4-22 4-117 LIGHTNING DETECTION CIRCUIT BOARD 4-23 4-119 RF OUTPUT POWER CONTROL CIRCUITRY 4-23

SECTION V MAINTENANCE

5-1 INTRODUCTION 5-1 5-3 SAFETY CONSIDERATIONS 5-1 5-6 FIRST LEVEL MAINTENANCE 5-1 5-8 ROUTINE MAINTENANCE 5-1 5-9 INSPECTION AND CLEANING 5-2 5-10 CONTROLLER BATTERY 5-2 5-11 AIR FILTERS 5-2 5-12 FLUSHING FANS 5-2 5-14 SPARK GAP 5-2 5-15 SECOND LEVEL MAINTENANCE 5-2 5-18 ELECTRICAL ADJUSTMENTS 5-4 5-20 TRANSMITTER FREQUENCY RE-PROGRAMMING 5-4 5-22 TROUBLESHOOTING 5-4 5-24 TRANSMITTER INDICATORS 5-5 5-25 RF POWER MODULE REMOVAL 5-8 5-26 TRANSMITTER TROUBLESHOOTING 5-8

PROCEDURES 5-27 TRANSMITTER COMPONENT LOCATIONS 5-8 5-28 COMPONENT REPLACEMENT PROCEDURE 5-13 5-34 INTEGRATED CIRCUITS 5-14

SECTION VI PARTS LIST

6-1 INTRODUCTION 6-1

SECTION VII DRAWINGS

7-1 INTRODUCTION 7-1

LIST OF TABLES

TABLE DESCRIPTION PAGE NO.

1-1 ELECTRICAL CHARACTERISTICS 1-5 1-2 PHYSICAL AND ENVIRONMENTAL 1-9

CHARACTERISTICS 3-1 AM-2.5E/AM-5E CONTROLS AND INDICATORS 3-1 3-2 ECU CONTROLS AND INDICATORS 3-3 3-3 POWER MODULE CONTROLS AND INDICATORS 3-11 5-1 AM-2.5E/AM-5E INDICATORS 5-5 5-2 AM-2.5E/AM-5E TROUBLESHOOTING 5-9 6-1 AM-2.5E/AM-5E REPLACEABLE PARTS LIST INDEX 6-1

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LIST OF ILLUSTRATIONS

FIGURE DESCRIPTION PAGE NO.

1-1 AM-2.5E TRANSMITTER 1-2 1-2 AM-5E TRANSMITTER 1-3 2-1 AM-2.5E TRANSMITTER INSTALLATION 2-3 2-2 AM-5E TRANSMITTER INSTALLATION 2-5 2-3 TRANSMITTER MOVING 2-7 2-4 COMPONENT INSTALLATION 2-9 2-5 EXCITER CIRCUIT BOARD PROGRAMMING 2-11 2-6 STEREO CIRCUIT BOARD PROGRAMMING 2-13 2-7 CONTROLLER CIRCUIT BOARD PROGRAMMING 2-14 2-8 REMOTE CONTROL AND AUDIO CONNECTIONS 2-17 2-9 AM-2.5E/AM-5E RF OUTPUT CONNECTIONS 2-21 2-10 AM-2.5E PRIMARY AC WIRING 2-23 2-11 AM-5E PRIMARY AC WIRING 2-24 2-12 ANTENNA LIGHTNING PROTECTION SYSTEM 2-27 2-13 TEST EQUIPMENT CONNECTIONS, POWER LEVEL 2-30

CALIBRATION 2-14 TEST EQUIPMENT CONNECTIONS, SEPARATION 2-31 2-15 EQUALIZATION LISSAJOUS PATTERNS 2-33 3-1 AM-2.5E/AM-5E CONTROLS AND INDICATORS 3-2 3-2 ECU CONTROLS AND INDICATORS 3-7 3-3 POWER MODULE CONTROLS AND INDICATORS 3-11 4-1 AM-2.5E BLOCK DIAGRAM 4-3 4-2 AM-5E BLOCK DIAGRAM 4-5 4-3 AM-2.5E/AM-5E POWER SUPPLY SIMPLIFIED 4-11

SCHEMATIC

4-4 AM-2.5E/AM-5E RF CIRCUITRY SIMPLIFIED 4-18

SCHEMATIC 5-1 REMOVING THE AIR FILTER 5-3 5-2 AM-2.5E COMPONENT LOCATOR 5-15 5-3 AM-5E COMPONENT LOCATOR 5-18 5-4 AM-2.5E/AM-5E ECU/POWER BLOCK/OUTPUT 5-21

NETWORK ASSEMBLY COMPONENT LOCATOR

PART II - TABLE OF CONTENTS

I - POWER SUPPLY ASSEMBLY

II - RF POWER MODULE

III - OUTPUT NETWORK

IV - EXCITER/CONTROLLER UNIT (ECU)

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Page 10

SECTION I

GENERAL INFORMATION

1-1. INTRODUCTION.

1-2. Information presented by this section provides a general description of the Broadcast

Electronics AM-2.5E and AM-5E transmitters and lists equipment specifications.

1-3. EQUIPMENT DESCRIPTION.

1-4. GENERAL.

1-5. The Broadcast Electronics AM-2.5E transmitter is a CE compliant 2.5 kW solid-state

C-QUAM stereo AM transmitter designed for continuous operation in the 522 kHz to

1705 kHz broadcast band (refer to Figure 1-1). The Broadcast Electronics AM-5E trans

mitter is a CE compliant 5 kW solid-state C-QUAM stereo AM transmitter designed for

continuous operation in the 522 kHz to 1705 kHz broadcast band (refer to Figure 1-2). The AM-2.5E and AM-5E transmitters consists of modular components assembled in a single cabinet. The modular components include: 1) an exciter/control unit, 2) an output network assembly, 3) power block assemblies containing two RF power modules and a star combiner assembly, 4) power supply panel assemblies, and 5) an AC distribution panel assembly. Specific AM-2.5E/AM-5E features include:

1. Built-in C-QUAM AM stereo circuitry.

2. High efficiency Class E solid-state RF power amplifier modules.

3. A high efficiency switching power supply.

4. Star combiner assembly. Each star combiner allows the removal of RF power modules without the use of dummy modules or bypass switches.

5. A built-in output matching network.

6. A CMOS digital controller with extensive VSWR detection and foldback circuitry which reduces carrier interruptions by weather conditions.

7. CE compliant design.

1-6.

1-7. Stereo Circuit Board. The ECU stereo circuit board is a modular plug-in assembly con

1-8. The stereo circuit board is designed with remote/local controlled mono left, mono right,

EXCITER/CONTROL UNIT. The transmitter exciter/control unit (ECU) is a modular as

sembly containing plug-in stereo, exciter, and controller circuit boards. In addition to the circuit boards, the ECU is equipped with forward and reflected power meters to provide transmitter output power status indications.

taining C-QUAM AM stereo circuitry. The C-QUAM stereo system is a mode of AM

stereo transmission utilizing amplitude modulated monaural (L+R) information and inde pendently quadrature modulated stereo (L-R) information. The results produce a stereo transmission system compatible with mono receivers.

mono L+R, and stereo modes of operation. Two equalization circuits are provided to allow the transmitter to be configured for operation into two different antennas.

C-QUAM is a registered trademark of Motorola Inc.

1-1

Page 11

FIGURE 1-1. AM-2.5E TRANSMITTER

597-1114-1

1-2

Page 12

FIGURE 1-2. AM-5E TRANSMITTER

1-3

597-1114-2

Page 13

1-9. Exciter Circuit Board. The ECU exciter circuit board is a modular plug-in exciter assem

bly. Instrumentation amplifiers provide balanced left and right channel transformerless audio inputs. The exciter carrier frequency is established by a digital frequency synthesiz er. The synthesizer is a phase-locked-loop circuit which provides extremely accurate and reliable carrier frequency operation. A PWM (pulse-width-modulation) circuit is used to generate an RF drive signal for application to a modulator circuit board in an RF power module. If a stereo circuit board failure is encountered or when the stereo circuit board is removed from the ECU chassis, the exciter circuitry is designed to automatically configure to monophonic operation.

1-10. Controller Circuit Board. All transmitter control operations are directed by the ECU con

troller circuit board. The controller circuit board consists of CMOS logic control and moni toring circuitry. The circuitry is designed to interface to all popular remote control systems such as the Broadcast Electronics VMC-16 remote control system.

1-11. The transmitter power is controlled by a power control circuit. The circuit allows the

transmitter to be operated at five power levels. A power trim circuit allows the transmitter output power to be adjusted to a precise level. An antenna interlock circuit is provided to prevent the transmitter from operating into an incorrect antenna. A reflected power detec tion circuit operates in association with the power control circuit to foldback the transmit ter power during high VSWR conditions. In addition to the reflected power detector, a lightning detector circuit is provided to mute the transmitter when high voltage is present at the transmitter output during a lightning storm.

1-12.

1-13.

1-14. The RF power modules are designed using Class E amplifier technology. A Class E ampli

1-15.

OUTPUT NETWORK ASSEMBLY. Matching of the transmitter impedance to the antenna is

accomplished by the output network assembly. The assembly is equipped with an LC T network to match the transmitter output to the antenna. A bandpass filter is pro vided to attenuate all harmonic frequencies to FCC, DOC, and CCIR levels. The assembly also contains the lightning detection circuit board, a lightning protection circuit board, and a directional coupler assembly.

RF POWER MODULE. The AM-2.5E and AM-5E transmitters are equipped with RF pow

er modules. A power module is a modular plug-in assembly containing two RF power am plifier circuit boards and one modulator circuit board. Each power module is equipped with MOSFET transistors to produce approximately 1375 watts of RF power.

fier exhibits high efficiency and provides superior audio performance. In addition to the superior efficiency and audio performance, the power modules are designed to be removed from the chassis for maintenance. The remaining power modules will provide full power to maintain on-air operation.

POWER SUPPLY. A modular switching power supply provides operating potentials for two

RF power modules. The power supply design uses an SCR controlled bridge to rectify the ac line voltage into a dc potential. The supply is filtered and routed to the RF power mod ules for control and regulation. A fault detection circuit monitors power supply activity for failure conditions. A separate modular switching power supply provides operating poten tials for the ECU circuitry.

1-16.

COMBINER ASSEMBLY. The AM-2.5E and AM-5E are equipped with a star combining

system. The system combines the outputs of the RF power modules to provide: 1) a 2.5 kW output in AM-2.5E models and 2) a 5 kW output in AM-5E models. If a power module is removed from the chassis, the remaining power modules will continue operation to main tain on-air operation.

1-4

Page 14

1-17. TRANSMITTER CONFIGURATIONS.

1-18. The AM-2.5E and AM-5E transmitters can be ordered in the following configurations:

P/N DESCRIPTION

907-2500-100 AM-2.5E 2.5 kW AM Transmitter for operation in

the 522 kHz to 1705 kHz broadcast band, 10 kHz spacing, 196V - 256V ac single phase supply.

907-5000-100 AM-5E 5 kW AM Transmitter for operation in

the 522 kHz to 1705 kHz broadcast band, 10 kHz spacing, 196V - 256V ac single phase supply.

1-19.

ACCESSORIES AND SPARE PARTS KITS.

1-20. The following text presents accessories and spare parts kits available for use with the

AM-2.5E and AM-5E transmitters.

P/N DESCRIPTION

977-0038 AM-2.5E/AM-5E recommended semi-conductor

kit.

977-0039 AM-2.5E 100% semi-conductor kit.

977-0040 AM-2.5E/AM-5E recommended spare parts kit.

Includes selected meters, switches, fuses, filters, etc. Does not include semi-conductors.

977-0041 AM-5E 100% semi-conductor kit.

907-0016-110 VMC-16 Voice Remote Control Unit, AM-10A/

AM-6A/AM-2.5E/AM-5E.

977-0037 Basic semi-conductor kit, AM-10A/AM-6A/

AM-1A/AM-2.5E/AM-5E.

1-21. EQUIPMENT SPECIFICATIONS.

1-22. Refer to Table 1-1 for electrical specifications or Table 1-2 for physical specifications of the

AM-2.5E and AM-5E transmitters.

TABLE 1-1. ELECTRICAL CHARACTERISTICS

(Sheet 1 of 5)

PARAMETER SPECIFICATION

RF POWER OUTPUT

AM-2.5E 12.5 W to 2.8 kW. Five preset power levels

AM-5E 25 W to 5.6 kW. Five preset power levels

available by local or remote control. Will operate at a reduced power output (30-50% typical) with one-half of the power modules.

1-5

Page 15

TABLE 1-1. ELECTRICAL CHARACTERISTICS

(Sheet 2 of 5)

PARAMETER SPECIFICATION

OUTPUT POWER REGULATION Less than 1% change in output power with vari-

ation of ac line input voltage from 196V to 252V ac.

RF CARRIER FREQUENCY 522 kHz to 1705 kHz (as ordered). RANGE Accommodates 9 kHz or 10 kHz channel spacing

(9 kHz spacing requires an optional crystal).

RF OUTPUT IMPEDANCE 50 Ohms, unbalanced. Matching network to

optimize VSWR of 1.5 : 1 at any phase angle and carrier frequency.

OUTPUT CONNECTOR Female 7/16 DIN connector. AM-5E Requires 7/8 inch RF transmission line with 7/16

male DIN connector.

AM-2.5E Requires 1/2 inch RF transmission line with 7/16

male DIN connector.

LOAD VSWR 1.5 : 1 at full carrier power. Will operate into a

higher VSWR with automatic power reduction. Open and short circuit protected.

HARMONIC AND SPURIOUS Meets or exceeds FCC, DOC, and CCIR requireSUPPRESSION ments when preceded by external NRSC-1 com-

patible audio low-pass filters.

CARRIER FREQUENCY ±3ppm, 0° to 50° C (+32° to +122° F).

STABILITY

CARRIER SHIFT Less than 1% at 95% negative modulation at

1 kHz.

TYPE OF MODULATION Pulse Width Modulation of L+R envelope with

integrated C-QUAM AM stereo. An RF input connector is also provided for an external stereo exciter.

OPERATING MODES Stereo, mono L+R, mono L, mono R, by local or

remote control.

MODULATION CAPABILITY

AM-2.5E Greater than 145% peak positive capability at

2.5 kW.

AM-5E Greater than 145% peak positive capability at

5 kW.

MODULATION INPUT INDICATION Peak reading, color coded, LED bar graph display

with an autorange feature for monitoring positive or negative input levels of four different audio channels (L/R or L+R/L-R).

AUDIO INPUT LEVEL +10 dBm, ±1 dB, L=R (or mono) to produce 100%

L+R envelope modulation. Other input levels can be accommodated.

1-6

Page 16

TABLE 1-1. ELECTRICAL CHARACTERISTICS

(Sheet 3 of 5)

PARAMETER SPECIFICATION

AUDIO INPUT IMPEDANCE 600 Ohms. Inputs are balanced, transformerless,

and resistive with passive RFI filtering. Other impedances can be accommodated.

AUDIO FREQUENCY ±0.5 dB, 20 Hz to 10 kHz at 90% negative

RESPONSE (MONOPHONIC) modulation (linear phase mode). +0.1 dB

-3 dB, 20 Hz to 10 kHz at 90% negative modulation, standard configuration.

AUDIO HARMONIC DISTORTION

Mono Less than 0.8%, 20 Hz to 10 kHz at rated power.

Less than 1.5%, 20 Hz to 10 kHz at 50% power. Less than 2.0%, 20 Hz to 10 kHz at 25% power. Less than 3.0%, 20 Hz to 10 kHz at 10% power. All mono audio harmonic distortion specifications are referenced to an audio input level which generates 90% modulation at 1 kHz (9 dBm).

Stereo Less than 1.5% at 50% single channel

modulation, 50 Hz to 10 kHz at rated power.

INTERMODULATION DISTORTION 1.2% or less at 1:1 ratio. 1.7% or less at 4:1 ratio. (MONO) 60/7000 Hz SMPTE standards with 85%

modulation at rated power.

CCIF INTERMODULATION 1.0% or less at 1:1 ratio. 4 kHz/5 kHz with 85% DISTORTION (MONO) modulation at rated power.

TRANSIENT INTERMODULATION 1.0% or less at 4:1 ratio. 2.96 kHz square wave DISTORTION (MONO) 8 kHz sinewave with 85% modulation at rated

power.

INCIDENTAL PHASE Less than 2.0 degrees (0.035 radians) average or 30 MODULATION dB (40 dB typical) below equivalent 100% L-R (STEREOPHONIC) C-QUAM modulation, 50 Hz to 10 kHz at rated

power. Measured with an audio input level which generates 95% negative L+R envelope modulation at 1 kHz (9.5 dBm).

STEREO SEPARATION -30 dB or greater, 50 Hz to 10 kHz. Measured

with 50% single channel modulation into a 50 ohm resistive load at rated power.

SQUAREWAVE OVERSHOOT

Mono 0.1% or less at 400 Hz, 90% modulation with high

frequency boost disabled.

Stereo 1.0% or less at 400 Hz, 50% single channel modu-

lation with high frequency boost disabled.

1-7

Page 17

TABLE 1-1. ELECTRICAL CHARACTERISTICS

(Sheet 4 of 5)

PARAMETER SPECIFICATION

SQUAREWAVE TILT 1.0% or less at 40 Hz. 1.5% or less at 20 Hz.

Measured with 90% negative modulation.

NOISE

Mono Greater than 65 dB below a reference level

equivalent to 100% negative modulation in a 22 Hz to 30 kHz bandwidth, unweighted.

Stereo Greater than 55 dB below a reference level

equivalent to 100% negative modulation of either left or right channel in a 22 Hz to 30 kHz bandwidth, unweighted.

AC INPUT VOLTAGE 196V to 252V ac 50/60 Hz, single phase.

Includes built-in MOVs for surge suppression.

AC POWER CONSUMPTION

AM-2.5E 3.3 kW, no modulation of 2.5 kW carrier.

2.05 kW, 100% modulation of 2.5 kW carrier. Measured at 2.5 kW into a 50 ohm resistive load at 220V ac. 0.9 power factor.

AM-5E 6.7 kW, no modulation of 5 kW carrier.

10 kW, 100% modulation of 5 kW carrier. Measured at 5 kW into a 50 ohm resistive load at 220V ac. 0.9 power factor.

OVERALL EFFICIENCY

AM-2.5E 75% or greater, 100% sinusoidal modulation

of carrier, ac line to RF output. Measured at into 2.5 kW a 50 ohm resistive load at 220V ac.

AM-5E 75% or greater, 100% sinusoidal modulation of

carrier, ac line to RF output. Measured at 5 kW into a 50 ohm resistive load at 220V ac.

SAFETY Meets IEC 215 specifications.

REGULATORY Meets CE specifications.

METERING

AM-2.5E Output Forward Power: 1) High scale - 0 to

3000 watts and 2) Low scale - 0 to 750 watts. Output Reflected Power: 1) High scale - 0 to 300 watts and 2) Low scale - 0 to 60 watts. Ac Line Voltage: Scale - 150 to 300 volts. AM-2.5

Forward Power Meter complies with FCC rule

78.1215 (a) within the 150 watt to 2800 watt range.

1-8

Page 18

TABLE 1-1. ELECTRICAL CHARACTERISTICS

(Sheet 5 of 5)

PARAMETER SPECIFICATION

METERING (CONT'D)

AM-5E Output Forward Power: 1) High scale - 0 to 6000

watts and 2) Low scale - 0 to 1500 watts. Output Reflected Power: 1) High scale - 0 to 600 watts and 2) Low scale - 0 to 150 watts. Ac Line Voltage: Scale - 150 to 300 volts. AM-5 Forward Power Meter complies with FCC rule

73.1215 (a) within the 300 watt to 5600 watt range.

RF MONITORING PROVISIONS 2 volts RMS nominal RF output sample into a 50

Ohm input. Adjustable from the transmitter front panel for each of the five power levels.

REMOTE INTERFACE Built-in interface for most control and monitoring

systems.

TABLE 1-2. PHYSICAL AND ENVIRONMENTAL CHARACTERISTICS

(Sheet 1 of 2)

PARAMETER SPECIFICATION

PHYSICAL

DIMENSIONS Width: 24.82 Inches (63.0 cm).

Height: 71.32 Inches (181.2 cm) Depth: 31.55 Inches (80.1 cm)

WEIGHT

AM-2.5E 410 Pounds (186 kg), unpacked. AM-5E 525 Pounds (238 kg), unpacked.

(1.2 m3).

CUBAGE 42.8Ft

ENVIRONMENTAL

COOLING

Type Low velocity air with disposable filters.

Requirements - AM2.5E/AM-5E 500 Cubic Feet Per Minute (14.15 m

OPERATING TEMPERATURE 0° to 50° C (+32° to +122° F)

OPERATING HUMIDITY 0 TO 95% (non-condensing)

/min).

1-9

Page 19

TABLE 1-2. PHYSICAL AND ENVIRONMENTAL CHARACTERISTICS

(Sheet 2 of 2)

PARAMETER SPECIFICATION

MAXIMUM ALTITUDE

60 Hz Models 0 to 10,000 feet above sea level (0 to 3048 Meters).

50 Hz Models 0 to 7,500 feet above sea level (0 to 2286 Meters).

NOTE -

For AM-2.5E, All specifications measured at 2.5 kW into a 50 ohm resistive load using Broadcast Electronics AS-10 modulation monitor. For AM-5E, All specifications measured at 5 kW into a 50 ohm resistive load using Broadcast Electronics AS-10 modulation monitor.

1-10

Page 20

SECTION II

INSTALLATION

2-1. INTRODUCTION.

2-2. This section contains information required for the installation and preliminary checkout of

the Broadcast Electronics AM-2.5E and AM-5E transmitters.

2-3. UNPACKING.

2-4. The equipment becomes the property of the customer when the equipment is delivered to

the carrier. Carefully unpack the transmitter. Perform a visual inspection to determine that no apparent damage has been incurred during shipment. All shipping materials should be retained until it is determined that the unit has not been damaged. Claims for damaged equipment must be promptly filed with the carrier or the carrier may not accept the claim.

2-5. The contents of the shipment should be as indicated on the packing list. If the contents are

incomplete, or if the unit is damaged electrically or mechanically, notify both the carrier and Broadcast Electronics.

2-6.

2-7. Table 1-2 provides environmental conditions which must be considered prior to transmit

2-8.

2-9. If outside air is to be used to cool the transmitter, the air inlet duct must be sized to allow

2-10. If the heated transmitter air is to be ducted from the room, the duct system must not

2-11. As a minimum requirement, any duct work must have a cross-sectional area equal to the

2-12.

2-13. The AM-2.5E and AM-5E transmitters are designed for operation from a 196V to 252V ac

ENVIRONMENTAL REQUIREMENTS.

ter installation. Refer to Table 1-2 in SECTION I, INTRODUCTION and ensure the transmitter is to be installed in an acceptable environment.

COOLING AIR REQUIREMENTS.

adequate air flow. The air must be dry and well filtered. If intake louvers are used, opera tion of the louvers must be electrically interlocked with the transmitter operation.

introduce any back-pressure on the equipment. Proper allowances for air flow will ensure that only a limited amount of heat is dissipated into the equipment interior. The duct sys tem must allow for a minimum air flow of: 1) 500 cubic feet of air per minute for AM-2.5E models and 2) 700 cubic feet of air per minute for AM-5E models.

exhaust area of the cabinet (refer to Figure 2-1 and 2-2). Sharp bends in the duct system will introduce back pressure and are not permissible. A radius bend must be used if a right angle turn is required. An exhaust fan may be used to overcome duct losses or over come wind pressures if the duct is vented to the outside.

PRIMARY POWER.

50/60 Hz single phase power source. Consult the local electric utility company to ensure that the correct service is provided before connection of the transmitter to the primary power source.

2-14. INSTALLATION.

2-15. Each transmitter is wired, operated, tested, and inspected at the factory prior to shipment

and is ready for installation when received. Prior to installation, this publication should be studied to obtain an understanding of the operation, circuitry, nomenclature, and installa tion requirements. Installation is accomplished as follows: 1) placement, 2) component installation, 3) circuit board programming, 4) remote control connections, 5) wiring,

6) initial checkout, and 7) preliminary operation and tuning.

2-1

Page 21

2-16. EQUIPMENT PLACEMENT.

2-17. The transmitter is designed with access holes in the top of the cabinet to allow for the

over-head ducting of ac power, RF transmission line, and ground strap wiring (refer to Figure 2-1/2-2). The floor must be capable of supporting the total transmitter weight of approximately 90 pounds per square foot. The floor support should be more than marginal to maintain proper cabinet alignment and reduce vibration.

2-18. Evaluate the installation site and determine the location of the transmitter. Once the

location is determined, refer to Figure 2-3 and use a forklift to move the transmitter to the desired location. After the transmitter is placed in the desired location, remove the ship ping skid as follows:

1. Refer to Figure 2-3 and remove the 5/16 inch shipping bolts securing the transmitter to the skid.

2. Once the bolts are removed, slide the transmitter off the skid.

3. Slide the transmitter to the exact location.

2-19.

COMPONENT INSTALLATION.

WARNING

ENSURE NO PRIMARY POWER IS CONNECTED TO THE TRANSMITTER BEFORE PROCEEDING.

WARNING

2-20. Selected components of the AM-2.5E and AM-5E transmitters have been removed to pre

vent damage during shipment. The components removed from the transmitter are shipped in separate containers.

2-21. Remove all tape, wire ties, string, and packing material used for shipment. In addition,

locate the component containers. To install the components, perform the following proce dures.

2-22.

ECU CIRCUIT BOARDS. The ECU circuit boards are removed for shipment. Locate the

circuit board shipping container. To re-install the circuit boards, proceed as follows:

CAUTION

THE TRANSMITTER MAY BE DAMAGED IF THE ECU CIRCUIT BOARDS ARE NOT

CAUTION

1. Refer to Figure 2-4 to determine the circuit board location.

2. Insert the circuit board in the appropriate location.

3. Firmly press the circuit board into the connector.

SECURELY SEATED INTO THE CONNECTORS.

4. Firmly press the circuit board into the connector again to ensure the circuit board is seated.

5. Repeat the procedure for each ECU circuit board.

CAUTION

REMOVING OR INSTALLING AN RF POWER MODULE WITH THE TRANSMITTER ENERGIZED MAY RESULT

CAUTION

2-23. RF POWER MODULES. Each RF power module is removed for shipment. Locate the RF

power module shipping containers. Refer to Figure 2-4 and re-install the modules.

IN DAMAGE TO THE MODULE.

2-2

Page 22

597-1114-7

FIGURE 2-1. AM-2.5E TRANSMITTER INSTALLATION

(2-3/2-4)

Page 23

597-1114-8

FIGURE 2-2. AM-5E TRANSMITTER INSTALLATION

(2-5/2-6)

Page 24

FIGURE 2-3. TRANSMITTER MOVING

2-24. POWER SUPPLY. The transmitter power supply circuit boards may be removed for ship

ment. If the power supply circuit boards have been removed, locate the shipping container. Install each circuit board as follows:

597-1114-27

CAUTION

THE TRANSMITTER MAY BE DAMAGED IF THE POWER SUPPLY CONNECTORS ARE NOT SE

CAUTION

CURELY SEATED INTO THE POWER SUPPLY CIRCUIT BOARD RECEPTACLES.

CAUTION

TO PREVENT DAMAGE TO THE POWER SUP PLY CIRCUIT BOARD, ENSURE THE CIRCUIT

CAUTION

BOARD IS INSERTED INTO THE MOUNTING PINS AND THE CAPACITORS ON THE CIRCUIT

CAUTION

SIDE OF THE BOARD ARE PLACED INTO THE PANEL CUTOUT PRIOR TO SLIDING THE CIR

CAUTION

CUIT BOARD TO SEAT THE MOUNTING SLOTS INTO THE PINS.

1. Locate the mounting slots in the power supply circuit board and insert the board into the power supply mounting pins on the power supply panel. Ensure the circuit board is inserted with the capacitors on the circuit side of the board placed into the panel cutout prior to seating the circuit board in the mounting pins.

2. Slide the circuit board in a position to seat the circuit board slots in the mounting pins.

2-7

Page 25

3. Secure the power supply circuit board mounting hardware.

4. Connect the power supply circuit board cables as follows:

A. Securely connect 16-pin connector P1 to J1 on the power supply circuit board.

B. Securely connect 12-pin connector P2 to J2 on the power supply circuit board.

C. Securely connect 24-pin connector P3 to J3 on the power supply circuit board.

5. Repeat the procedure for each power supply circuit board.

2-25.

2-26. CIRCUIT BOARD PROGRAMMING.

2-27. The AM-2.5E and AM-5E transmitters are designed with programmable transmitter oper

2-28.

2-29. External Stereo Generator Select. Programmable header J7 programs the circuitry if:

2-30. Carrier Frequency Programming. Eight position switch S2 programs the exciter carrier

2-31. PWM Frequency Programming. Four position switch S1 programs the PWM frequency.

2-32. Frequency Synthesizer Programming. Programmable header J6 determines the frequency

2-33. Pilot Tone Programming. Programmable header J5 establishes the pilot tone frequency for

2-34. High-Pass Filter Defeat. Left channel programmable header J12 and right channel pro

2-35. High Frequency Boost Defeat. Left channel programmable header J2 and right channel

BATTERY INSTALLATION. The ECU is equipped with a battery system. Refer to Figure

2-4 and install the battery in the battery receptacle.

ating characteristics. The operating characteristics are determined by the programmable circuitry on the ECU circuit boards (refer to Figure 2-4). Refer to the following text and program the circuitry for the desired operating characteristics.

EXCITER CIRCUIT BOARD. Exciter circuit board programming is presented in Figure

2-5. Refer to Figure 2-5 and program the circuit board as required.

1) an external stereo generator is to be used with the transmitter or 2) the internal stereo circuit board is to be used with the transmitter. The transmitter is shipped with the circuit programmed for the internal stereo circuit board operation.

frequency. The switch is programmed for the station frequency at the factory. Refer to the factory test data sheets to check the programming of the switch. If the switch program ming is not identical to programming recorded in the factory test data sheets, contact the Broadcast Electronics Customer Service Department.

Refer to the factory test data sheets to check the programming of the switch.

synthesizer band of operation. Refer to the factory test data sheets to check the program ming of the header.

10 kHz carrier frequency operation and 9 kHz carrier frequency operation. Refer to the factory test data sheets to check the programming of the header.

grammable header J13 control an exciter second order 10 Hz high-pass filter. The highpass filter is provided to remove low frequency residual products from specific audio pro cessing units. The filter is shipped from the factory in the enabled position. Evaluate the audio processor and determine if low frequency residual products are present at the output of the audio processing unit. If no low frequency residual products are present, refer to Figure 2-5 and disable the high pass filter.

programmable header J3 control an exciter high frequency boost circuit. The high frequen cy boost circuit provides increased high frequency response to compensate for a Bessel fil ter in the PWM modulator. If the high frequency boost circuit is enabled to compensate for the filter, the circuit will result in a compromise between the frequency and transient re sponse performance. If the high frequency boost circuit is enabled, the transmitter fre quency response will increase approximately 2 dB at 10 kHz and the transient response will degrade. If the high frequency boost circuit is disabled, the transmitter frequency re sponse will decrease approximately 2 dB at 10 kHz and the transient response will im prove. The high frequency boost circuit is shipped from the factory in the disabled posi tion.

2-8

Page 26

597-1114-14

FIGURE 2-5. COMPONENT INSTALLATION

(2-9/2-10)

Page 27

2-11

597-1111-11

FIGURE 2-5. EXCITER CIRCUIT BOARD PROGRAMMING

Page 28

2-36. Monophonic Transmitter Operation Channel Select. Programmable header J4 selects

either the left or right audio channel when the transmitter is operating in the monophonic mode with the stereo circuit board removed. The transmitter is shipped with the left chan nel audio selected for monophonic operations.

2-37. STEREO CIRCUIT BOARD. Stereo circuit board programming is presented in Figure 2-6.

Refer to Figure 2-6 and program the circuit board as required.

2-38. Antenna C Equalization Select. Programmable header J6 selects equalization circuit 1 or

equalization circuit 2 for operation with antenna C. The transmitter is shipped with equal ization circuit 2 configured for operation with antenna C.

2-39. Bandpass Filter Alignment. Programmable header J5 configures the bandpass filter for

alignment. The jumper must be installed in position 1-2.

2-40. Bandpass Filter Programming. Four position switches S2 through S4 program the band

pass filter. Refer to the factory test data sheets to check the programming of the switches.

2-41. Equalization Control Select. Programmable header J7 configures the equalization circuit

ry for either a momentary or constant antenna status signal. The transmitter is shipped with equalization control circuitry configured for a constant status signal.

2-42. CONTROLLER CIRCUIT BOARD. Controller circuit board programming is presented in

Figure 2-7. Refer to Figure 2-7 and program the circuit board as required.

2-43. Power Level Trim Reset Select. Programmable header J12 determines if the power level

control circuit is to reset when a power level switch/indicator is depressed. If the circuit is programmed to reset, the previous raise/lower information will be deleted and the trans mitter will operate at the selected power level. If the circuit is programmed to retain the previous raise/lower information, the transmitter will operate above or below the selected power level as determined by previous raise/lower operations. For example, the transmit ter is operating at power level 4 with the power level raised 5% by the power level raise/ lower circuit. When power level 5 switch/indicator is depressed, the transmitter will oper ate at 5% above the power level 5 output due to the previously retained raise/lower in formation. The transmitter is shipped with power level trim reset circuit configured to re set.

2-44. Antenna Power Level Programming. Switches S1, S2, and S3 assign power levels to a spe

cific antenna. This programs the antenna interlock circuit to the station antenna system to prevent the transmitter from operating into an antenna at an incorrect power level. Switch S1 programs the power levels for antenna A. Switch S2 programs the power levels for antenna B. Switch S3 programs the power levels for antenna C. Power level 2 is as signed to an antenna by switch 1 on S1, S2, and S3. Power level 3 is assigned to an anten na by switch 2 on S1, S2, and S3. Power level 4 is assigned to an antenna by switch 3 on S1, S2, and S3. Power level 5 is assigned to an antenna by switch 4 on S1, S2, and S3. Power level 1 is assigned to each antenna. Evaluate the antenna system and program the circuit as required.

2-45. AC Power Failure Automatic Transmitter Shutdown Time. Programmable headers J4, J5,

J6, and J7 program the transmitter ac power failure automatic transmitter shutdown timer circuit. The circuit is designed to automatically operate the transmitter to off during a power failure after a specific time delay programmed by headers J4, J5, J6, and J7. J4 programs the circuit for a 1 minute shutdown time. J5 programs the circuit for a 4.5 min ute shutdown time. J6 programs the circuit for a 17 minute shutdown time. J7 programs the circuit for a 68 minute shutdown time. The transmitter is shipped from the factory for a 1 minute shutdown time.

2-46. Antenna Interlock Control Select. Programmable header J1 controls the antenna inter

lock circuit. The circuit can be disabled if the transmitter is to operate into only one anten na. The transmitter is shipped from the factory with the antenna interlock circuit dis abled.

2-12

Page 29

FIGURE 2-6. STEREO CIRCUIT BOARD PROGRAMMING

597-1111-6

2-13

Page 30

2-14

597-1112-5

FIGURE 2-7. CONTROLLER CIRCUIT BOARD PROGRAMMING

Page 31

2-47. Power Level Reference. Programmable headers J10 and J19 provide a reference for the

power level circuit. For AM-2.5E/AM-5E transmitters, ensure jumpers P10 and P19 are removed.

2-48. Power Level 3 Assignment. Programmable header J8 and J9 control the assignment for

the power level 3 switch/indicator. For the AM-2.5E, the power level 3 switch/indicator can be programmed to control power from: 1) 250 watts to 1250 watts or 2) 750 watts to 2800 watts. For the AM-5E, the power level 3 switch/indicator can be programmed to con trol power from: 1) 500 watts to 2500 watts or 2) 1500 watts to 5600 watts. The power level 3 switch/indicator is shipped from the factory to control power from: 1) 250 watts to 1250 watts on AM-2.5E models and 2) 500 watts to 2500 watts on AM-5E models. Pro gram jumpers P8 and P9 as required.

2-49. Remote Reflected Power Sample Voltage Programming. Programmable header J3 con

trols the remote reflected power meter sample voltage. The remote reflected power sample can be programmed for a +5.0 volt dc or +2.5 volt dc full-scale meter indications. The transmitter is shipped from the factory programmed for +5.0 volt dc full-scale remote re flected power meter indications.

2-50. Remote Forward Power Sample Voltage Programming. Programmable header J2 con

trols the remote forward power meter sample voltage. The remote forward power sample can be programmed for a +5.0 volt dc or +2.5 volt dc full-scale meter indications. The transmitter is shipped from the factory programmed for +5.0 volt dc full-scale remote for ward power meter indications.

2-51. High Forward Power Defeat. Programmable header J11 controls the high forward power

detector circuit. Ensure jumper P11 is removed.

2-52. Reflected/Forward Power Sample Programming. Programmable headers J15, J16, J17,

and J18 control the reflected and forward power sample levels. Headers J15 and J17 con trol the forward power sample. Headers J16 and J18 control the reflected power sample. For AM-2.5E models: 1) remove jumpers P15 and P16 and 2) install jumpers P17 and P18. For AM-5E models: 1) install jumpers P15 and P16 and 2) remove jumpers P17 and P18.

2-53. Forward Power Reference Voltage Programming. Programmable headers J13 and J14

establish the forward power reference level for a comparator circuit. For AM-2.5E/AM-5E models, ensure jumpers P13 and P14 are installed.

2-54. Temperature Sense. Header J20 controls the temperature sense sample voltage. Ensure

P20 is removed for all models.

2-55.

POWER SUPPLY CIRCUIT BOARD. The power supply circuit board programming is pre

sented in the following text. Refer to the following text to check the power supply circuit board programming.

2-56. Future Corrector Circuit. Programmable headers J9 and J10 establish parameters for a

future corrector circuit. Ensure jumper P9 is removed and P10 is installed.

2-57. Model Programming. Programmable headers J5 through J8 establish parameters for dif

ferent AM E-Series transmitters. Refer to the following text for the programming information.

TRANSMITTER J5 J6 J7 J8

AM-2.5E Not Used Not Used Not Used Not Used

AM-5E Not Used Not Used Not Used Not Used

2-15

Page 32

2-58. REMOTE CONTROL.

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BE FORE PROCEEDING.

WARNING

2-59. GENERAL. The AM-2.5E and AM-5E transmitters are designed for complete remote con

trol operations (refer to Figure 2-8 ). The transmitters will interface with almost any re mote control unit such as the Broadcast Electronics model VMC-16 voice remote control system. The following text presents a description of the transmitter remote control func tions and indications. The remote control connections are located at 25-pin D-type con nectors J1 and J2. J1/J2 are located on the transmitter top-panel. The remote control functions are activated using a +5 to +15 volt dc signal. The remote indication functions:

1) require current limiting resistors and 2) provide up to 100 mA for indicators. A +5 volt supply is provided at J1 for remote control operations.

2-60. Power Level Controls/Indicators. The transmitter is designed with five customer adjust

able operating power controls. The controls are located at J1-1 through J1-5. A +5 to +15 volt dc signal is required to activate the desired function.

2-61. Indications of power level control operations are located at J1-7 through J1-11. The power

level status indicators will go LOW (0 volts dc) when activated.

2-62. Transmitter Off Control/Indicator. The transmitter off control is located at J1-6. A +5 to

+15 volt dc signal is required to operate the transmitter to off. The indicator for the trans mitter off control is located at J1-14. The off indicator will go LOW (0 volts dc) when acti vated.

2-63. Power Level Raise/Lower Controls. The transmitter is designed with raise and lower con

trols to adjust the transmitter output power level. The controls are equipped with ability to raise/lower power from 10% to 15% of the selected output power level. The controls are located at J1-15 and J1-16. A +5 to +15 volt dc signal is required to activate the desired function.

2-64. Antenna Interlock Input. The antenna interlock inputs are designed for the connection of

the status signals from antenna A, B, and C. The inputs are located at J1-19 through J1-21. The inputs require a +5 to +15 volt dc signal to indicate an antenna ready status.

2-65. Transmitter Mute Input. The transmitter mute input is designed to mute the transmitter

when activated. The input is located at J1-22. The input requires a +5 to +15 volt dc sig nal to mute the transmitter.

2-66. Remote Failsafe Input. The remote failsafe input is designed for the remote control unit

failsafe control line. The input is located at J1-23. The input requires a +5 to +15 volt dc signal to indicate an enabled remote control unit.

2-67. External Interlock Input. The external interlock input is for the connection of an interlock

external to the transmitter. The input is located at J1-24. The input requires a +5 to +15 volt dc signal to indicate a closed interlock.

2-68. Interlock +5V. The interlock +5 volt supply is provided for the external interlock. The +5

volt supply is located at J1-25.

2-69. Exciter Mode Controls/Indicators. The transmitter exciter is designed to be operated in

the mono left, mono right, mono L+R, or stereo modes of operation. The controls are lo cated at J2-1 through J2-4. A +5 to +15 volt dc signal is required to activate the desired function.

2-70. Indications of exciter modes of operations are located at J2-5 though J2-8. The exciter

mode indicators will go LOW when activated.

2-71. Remote Forward/Reflected Power Meter Indications. Remote reflected power meter indi

cations are located at J2-9 and J2-10. The indications are designed to be programmed for +5 volt dc full-scale meter indications or +2.5 volt dc full-scale meter indications.

2-16

Page 33

FIGURE 2-8. REMOTE CONTROL AND AUDIO CONNECTIONS (SHEET 1 OF 2)

597-1114-3

2-17

Page 34

FIGURE 2-8. REMOTE CONTROL AND AUDIO CONNECTIONS (SHEET 2 OF 2)

597-1114-3A

2-18

Page 35

2-72. Remote Enabled Indications. The remote enabled indicator provides a signal to indicate

the status of transmitter remote control operations. The remote enabled indicator is lo cated at J2-11. The indicator will go LOW to indicate when remote control operations are enabled.

2-73. Maintenance Indications. The maintenance indicator provides a signal to indicate when

a transmitter power supply or an RF power module is removed from the transmitter for maintenance. The maintenance indicator is located at J2-12. The indicator will go LOW (0 volts dc) to indicate when a power supply is removed for maintenance.

2-74. Lightning Indications. The lightning indicator provides a signal to indicate when a greater

than: 1) 1500 volt potential is present at the output for AM-2.5E models or 2) 2100 volt potential is present at the output for AM-5E models. The lightning indicator is located at J2-13. The indicator will go LOW (0 volts dc) to indicate when a lightning potential is pre sent at the transmitter output.

2-75. 1.2 : 1 VSWR Indications. The 1.2 : 1 VSWR indicator provides a signal to indicate when a

greater than 1.2 : 1 VSWR condition is present at the transmitter output. The 1.2 : 1 indi cator is located at J2-14. The indicator will go LOW (0 volts dc) to indicate when a 1.2 : 1 VSWR condition is present at the transmitter output.

2-76. Exciter/PWR Supply/PWR Module Fault Indications. The exciter, power supply, and power

module fault indicators provide signals to indicate when an exciter, power supply, or a power module fault has occurred. The exciter, power supply, and power module fault indi cators are located at J2-15 through J2-17. The indicators will go LOW (0 volts dc) to indicate when an exciter, power supply, or a power module fault has occurred.

2-77. RFL PWR High Indications. The reflected power high indicator provides a signal to indicate

when: 1) 100 watts of reflected power is present at the transmitter output for AM-2.5E models or 2) 200 watts of reflected power is present at the transmitter output for AM-5E models. The high reflected power indicator is located at J2-18. The indicator will go LOW (0 volts dc) to indicate when a reflected power high condition is present at the transmitter output.

2-78. RFL PWR Emergency Indications. The reflected power emergency indicator provides a sig

nal to indicate when greater than: 1) 500 watts of reflected power is present at the output of the AM-2.5E transmitter or 2) 1000 watts of reflected power is present at the output of the AM-5E transmitter. The reflected power emergency indicator is located at J2-19. The indicator will go LOW (0 volts dc) to indicate when a reflected power emergency condition is present at the transmitter output.

2-79. Overtemp Indications. The overtemp indicator provides a signal to indicate when the

transmitter temperature is greater than 70°C. The overtemp indicator is located at J2-20.

The indicator will go LOW (0 volts dc) to indicate when the transmitter temperature is

greater than 70°C.

2-80. Foldback Indications. The transmitter is designed to automatically reduce power when

one of the following fault condition occurs: 1) high reflected power, 2) high forward power,

3) high temperature, or 4) detection of a high voltage by the lightning circuit. The foldback indicator is located at J2-21. The indicator will go LOW (0 volts dc) to indicate when the transmitter is in a foldback condition.

2-81. Alarm Status Indications. The alarm status provides a signal to indicate when a fault or

foldback condition occurs. The alarm status indicator is located at J2-22. The indicator will go LOW (0 volts dc) to indicate when the transmitter is in a fault or foldback condition.

2-82. Alarm Reset Control. The alarm reset control is designed to reset the fault detection cir

cuitry. The alarm reset control is located at J2-23. A +5 to +15 volt dc signal is required to activate the function.

2-19

Page 36

2-83. Emergency Off Indications. The emergency off indicator provides a signal to indicate

when the transmitter is operated to off by any condition or event other than the use of the off switch. These conditions/events include: 1) an overcycle off condition, 2) a power sup ply emergency condition, or 3) an open interlock condition. A power supply emergency con dition is when all the power supplies in the transmitter encounter faults. The emergency off indicator is located at J2-24. The indicator will go LOW (0 volts dc) to indicate when an emergency off condition is encountered.

2-84.

2-85. Wiring consists of connecting audio, the RF transmission line, and ac power to the trans

2-86. AUDIO INPUT CONNECTION. The AM-2.5E and AM-5E transmitters are equipped

WIRING.

mitter. Refer to the following text and connect the wiring to the transmitter.

with electronically balanced 600 Ohm left and right channel audio inputs. The audio in puts are located on the transmitter top-panel at J3 (refer to Figure 2-8). The inputs are designed to accept a +10 dBm signal at 600 Ohms.

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BE FORE PROCEEDING.

WARNING

2-87. Audio is interfaced to the transmitter by: 1) selecting the appropriate cable and 2) connect

ing the cable to the terminals of 9-pin D-type connector J3. J3 is located on the transmit ter top-panel. To interface audio to the transmitter: 1) use Belden 8760 cable or equiva lent and 2) refer to Figure 2-8 and connect the audio to the transmitter as follows:

1. Connect the plus signal line to the + terminal.

2. Connect the minus signal line to the - terminal.

3. Connect the shield to ground at the audio source end.

2-88.

EXTERNAL STEREO RF INPUT. The transmitter is equipped with an external stereo RF

input on the transmitter top-panel (refer to Figure 2-9). The input is designed for the con nection of an external stereo generator or reference oscillator with a signal level from 5 to 15 volts peak-to-peak. If an external stereo signal/reference is to be applied to the trans mitter, connect the signal to the EXTERNAL RF INPUT connector on the transmitter top-panel and program jumper P7 on the exciter circuit board in position 1-2.

2-89.

2-90.

2-91.

AM-2.5E/AM-5E RF TRANSMISSION LINE CONNECTION. The AM-2.5E/AM-5E

transmitter RF output connection is located on the transmitter top-panel (refer to Figure 2-9). The AM-5E requires 7/8 inch transmission line with a 7/16 male DIN connector. The AM-2.5E requires 1/2 inch transmission line with a 7/16 male DIN connector. To con nect the RF transmission line to the transmitter, refer to Figure 2-9 and connect the 7/16 male DIN type connector to the RF OUT connector on the transmitter top-panel.

EXTERNAL INTERLOCK. The AM-2.5E/AM-5E is equipped with an external interlock

such as for a test load. The interlock will turn off the transmitter RF output when opened. The interlock is located at J1-24 and J1-25 on the transmitter top-panel. Refer to External Interlock Input and Interlock +5v in the REMOTE CONTROL section of the preceding text and perform the procedures to connect equipment to the transmitter exter nal interlock.

MODULATION MONITOR. The modulation monitor connection is located on the trans

mitter top-panel. Refer to Figure 2-9 and connect the modulation monitor to the MOD MONITOR SAMPLE OUTPUT receptacle.

2-20

Page 37

2-21

FIGURE 2-9. AM-2.5E/AM-5E RF OUTPUT CONNECTIONS

597-1114-22

Page 38

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BE FORE PROCEEDING.

WARNING

ENSURE AN EARTH GROUND CONDUCTOR IS SE CURELY CONNECTED TO THE TRANSMITTER AC

WARNING

2-92. AC POWER CONNECTIONS. The AM-2.5E transmitter requires a single-phase source

of 196V to 252V ac, 50 Hz or 60 Hz at 75 Amperes. The AM-5E transmitter requires a single-phase source of 196V to 252V ac, 50 Hz or 60 Hz at 125 amperes. For operating safety, the power source must be routed to the transmitter through a fused power discon nect (refer to Figures 2-10 and 2-11).

WARNING

GROUND LUG.

ENSURE PRIMARY POWER IS DISCONNECTED BE FORE PROCEEDING.

WARNING

2-93. Main ac Input -AM-2.5E. Refer to Figure 2-10 and connect the 75 Ampere service to ac

input/control device S1 through a fused service disconnect as shown. Ensure a utility com pany ground conductor is securely connected to the transmitter common ground system and the ac service ground wire is securely connected to the ac ground lug as shown.

2-94. Main ac Input - AM-5E. Refer to Figure 2-11 and connect the 125 ampere service to ac

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BE FORE PROCEEDING.

WARNING

ENSURE AN EARTH GROUND CONDUCTOR IS SE CURELY CONNECTED TO THE TRANSMITTER

WARNING

2-95. GROUND. The transmitter is equipped with a cabinet ground system for operating safety.

The ground system requires the connection of an earth ground. Refer to Figures 2-10 and 2-11 and connect an earth ground to the cabinet ground lug as shown using a 2 inch (5.08 cm) wide copper strap.

2-96.

TRANSMITTER SITE LIGHTNING PROTECTION SYSTEM CHECKOUT.

CAUTION

GROUND LUG.

THE TRANSMITTER SITE LIGHTNING PROTECTION SYSTEM MUST BE INSPECTED AND IN PROPER

CAUTION

WORKING CONDITION FOR RELIABLE TRANSMIT TER OPERATION.

2-97. For reliable transmitter operation, the transmitter site lightning protection system must

be inspected and in proper working condition. Due to the solid-state design of the trans mitter, high voltage potentials from lightning activity can cause severe damage to the transmitter circuitry. Therefore, perform the following procedures to inspect and improve the lightning protection system at the transmitter site. Refer to the NAB Radio Handbook for additional transmitter site lightning protection system information.

2-22

Page 39

2-23

FIGURE 2-10. AM-2.5E PRIMARY AC WIRING

597-1114-10

Page 40

2-24

FIGURE 2-11. AM-5E PRIMARY AC WIRING

597-1114-9

Page 41

2-98. ANTENNA BALL-GAP LIGHTNING ARRESTOR. Each tower in the antenna system must

be equipped with a ball-gap lightning arrestor (refer to Figure 2-12). The ball-gap arrestor is designed to safely conduct lightning potentials to ground. Inspect the ball-gap arrestors by performing the following procedures.

2-99. Ball-Gap Position. The antenna ball-gap lightning arrestor must be aligned horizontally.

Do not align the ball-gaps vertically. Vertical alignment allows rain water to collect on the balls. This reduces the gap separation and results in arcing during rain activity.

2-100. Ball-Gap Separation. The antenna ball-gap lightning arrestor must be adjusted for the

proper separation. If the ball-gap separation is too wide, the arrestor will not function. If the ball-gap separation is too narrow, the arrestor will arc during normal transmitter op eration. As a general rule: 1) a separation of approximately 0.020 in. for each peak kilo volt at the transmitter tower is required or 2) 0.125 inch for each 9.4 peak kilovolt at the transmitter tower is required.

2-101. The recommended method for ball-gap separation adjustment is to adjust the gap to pre

vent arcing during peak modulation activity. To adjust the separation, proceed as follows:

1. Adjust the ball-gap separation using the general rule presented in the preceding text.

2. Operate the transmitter at peak modulation and check the ball-gap for arcing activity.

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER BEFORE PROCEEDING.

WARNING

3. Operate the transmitter to off.

4. Adjust the ball-gap separation as follows:

A. If no arcing activity is detected, reduce the ball-gap separation.

B. If arcing activity is detected, increase the ball-gap separation.

5. Repeat the procedure until the ball-gap separation is adjusted for the smallest gap possible without arcing during peak modulation activity.

2-102. ANTENNA-TUNING-UNIT SPARK-GAP LIGHTNING ARRESTOR. The

antenna-tuning-unit (ATU) must be equipped with a spark-gap lightning arrestor (refer to Figure 2-12). The spark-gap arrestor can be: 1) a ball-gap type or 2) a horn type. Ad just the spark-gap for the smallest possible gap without arcing during peak modulation activity.

2-103.

TRANSMITTER SITE GROUNDING SYSTEM. The transmitter site grounding system must

be properly connected for reliable transmitter operation. A typical transmitter site ground ing system is shown in Figure 2-12. Perform the following procedures to ensure the grounding system connections are secure.

1. Ensure the antenna base ground strap is securely connected to the antenna ground plane radials.

2. Ensure the antenna ball-gap lightning arrestor is securely connected to the lightning ground rod system and to the antenna ground plane radials.

3. Ensure the ATU ground and the station RF ground is securely connected to the antenna ground plane radials.

2-25

Page 42

2-104. CABLE PROTECTION. The ac line cable, audio/control cables, and the RF output trans

mission line require a combination of MOV and ferrite core protection to prevent the entry of lightning potentials (refer to Figure 2-12). Refer to the following text to install MOV and ferrite cores on the cables to prevent the conductance of lightning potentials. Ensure MOVs are connected from the ac line and audio/control cable conductors to the station RF ground as shown. The MOVs should be rated for 20,000 Ampere surges (BE P/N 140-0032).

2-105. Ferrite Core. The ac line cable, the audio/control cables, and the RF output transmission

line also require the placement of ferrite cores. The cores are designed to create a high impedance for undesired current paths such as lightning. Ferrite cores for placement on ac line audio/control and RF output transmission line cables are located in the accessory parts kit. Locate the ferrite cores and install the cores by performing the following procedures.

2-106. Modulation Monitor Core. One 375-0009-001 ferrite core is designed to be installed on

the modulation monitor cable. Install the core on the modulation monitor cable by:

1) routing the cable through the core and 2) wrapping the cable to create one cable loop around the core. The core can be installed at any location on the cable.

2-107. Audio/Remote Control/Status Core. A second 375-0009-001 ferrite core is designed to be

installed on the audio and remote control/status cables. Install the core on the audio and remote control/status cables by: 1) routing the cables through the core and 2) if possible, wrapping the cables to create one cable loop cable around the core. The core can be installed at any location on the cables.

2-108. Ac Input Core. A 375-0007-001 ferrite core is shipped with the unit for installation on

the transmitter ac input cable. Install the core by routing: 1) all ac line phase cables through the core or 2) all ac line phase cables and ground cable through the core. Place the core at any location between the wall mounted fused disconnect and the transmitter ac in put switch.

2-109. RF Output Core. A second 375-0007-001 ferrite core is designed to be installed on the

transmitter RF output transmission line cable. Install the core by routing the RF output cable through the core. Place the core at any location between the transmitter RF output connector and the next equipment connection in the RF output system such as the antenna phasing system. It is recommended the core be placed outside the transmitter cabinet.

2-110. ANTENNA RF FEED LINE. Check the antenna RF feed line between the ATU and the

tower. Ensure the line contains one or more one foot diameter loops. The loops function as a series inductance and increase the impedance of the line.

2-111. TRANSMISSION LINE AND ANTENNA CHECKOUT.

CAUTION

2-112. The transmission line and antenna must be inspected and in proper working condition for

reliable transmitter operation. Perform the following procedures to inspect the transmis sion line and antenna.

2-113.

2-114.

ANTENNA VSWR. The AM-2.5E/AM-5E are designed to operate into an antenna with a

maximum VSWR of 1.5 : 1. Check the antenna VSWR. If the VSWR is greater than

1.5 : 1, contact the Broadcast Electronics Customer Service Department. Typically, the an tenna will require the installation of an additional tuning unit to reduce the antenna VSWR.

COAXIAL SWITCH CONTROLLER. To prevent damage to the transmitter, the transmit

ter must be muted during any antenna change sequence. Inspect the motorized coaxial switch controller and ensure the unit outputs a +5 volt to +15 volt mute signal. Ensure the mute signal is applied to the transmitter.

THE TRANSMISSION LINE AND ANTENNA MUST BE INSPECTED AND IN PROPER WORKING CONDITION FOR RELIABLE TRANSMITTER OPERATION.

2-26

Page 43

2-27

FIGURE 2-12. ANTENNA LIGHTNING PROTECTION SYSTEM

597-1111-36

Page 44

2-115. ATU AND PHASOR CHECKOUT. Inspect the ATU and the antenna phasor unit (if

installed in the system) for arcing activity during peak modulation periods. Repair or re place any devices to prevent arcing during peak modulation periods.

2-116.

INITIAL CHECKOUT.

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BE FORE PROCEEDING.

WARNING

2-117. Prior to performing the preliminary operating procedures, the transmitter should be

checked to ensure all installation and connection procedures have been performed. To check the transmitter, proceed as follows:

A. Ensure all ECU circuit boards, RF power modules, and power supply circuit boards

are installed.

B. Ensure the RF output transmission line is connected to the transmitter output

network.

C. Ensure the station earth ground is connected to the transmitter ground terminal.

D. Ensure all audio and control cables are connected to the transmitter.

E. Ensure the modulation monitor is connected to the transmitter.

F. Ensure all ac power connections are secure.

G. Ensure the station RF output transmission line system and antenna are in proper

working condition.

H. Ensure the antenna lightning protection system is in proper working condition.

2-118.

2-119. Adjust the transmitter for operation with the equipment at the installation site as follows:

PRELIMINARY OPERATION AND ADJUSTMENT.

WARNING

THE TRANSMITTER POWER SUPPLY OPERATES FROM A HIGH FLOATING GROUND POTENTIAL.

WARNING

NEVER OPERATE THE TRANSMITTER WITH THE REARDOOR OPEN.

2-120. TUNING. The transmitter must be adjusted to operate into the station antenna. To tune

the transmitter, proceed as follows:

2-121. Operate the rear-door ac on/off switch to ON. The ECU and power module front-panel

indicators will illuminate.

2-122. Depress the power level 1 switch/indicator to illuminate the switch/indicator.

2-123. Operate the FORWARD POWER meter switch to LOW and observe the forward power

indication.

2-124. Operate the REFLECTED POWER meter switch to LOW and observe the reflected power

indication.

2-125. Tune the transmitter by adjusting the TUNING and LOADING controls as required for a

minimum reflected power indication on the REFLECTED POWER meter.

2-28

Page 45

2-126. POWER LEVEL AND MODULATION MONITOR CALIBRATION ADJUSTMENTS. The

transmitter power levels are adjusted to the levels specified in the sales order at the factory. If no power levels are specified, the levels are adjusted as follows:

AM-2.5E AM-5E

Power level 1 = 500 watts Power level 1 = 1000 watts

Power level 2 = 1000 watts Power level 2 = 2000 watts

Power level 3 = 1500 watts Power level 3 = 3000 watts

Power level 4 = 2000 watts Power level 4 = 4000 watts

Power level 5 = 2500 watts Power level 5 = 5000 watts

2-127. If desired, the transmitter power levels can be changed at any time. If the transmitter

power levels are adjusted, the modulation monitor output must also be re-calibrated. To change the power level and re-calibrate the modulation monitor output, proceed as follows:

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER BEFORE PROCEEDING.

WARNING

2-128. Operate the transmitter rear-door ac on/off control switch to OFF and open the rear-door.

2-129. Refer to Figure 2-13 and connect the test equipment to the transmitter modulation connec

tor as shown.

2-130. Operate the transmitter rear-door ac on/off control switch to ON.

2-131. Depress power level control 1 switch/indicator to illuminate the switch/indicator.

2-132. Operate the FORWARD POWER meter switch to LOW or HIGH as required and observe

the forward power indication.

2-133. Refer to Figure 2-7 and adjust the power level 1 control to obtain the desired indication on

the FORWARD POWER meter. The control range is from: 1) 250 watts to 1250 watts on AM-2.5E models and 2) 500 watts to 2500 watts on AM-5E models.

2-134. Refer to Figure 3-1 in SECTION III, OPERATION and adjust the power level 1 modula

tion monitor calibration control for a 5.7 volt peak-to-peak signal on the oscilloscope.

2-135. Repeat the procedure for power levels 2 through 5. The power level control ranges are as

follows:

AM-2.5E

1. Power level 2 - 250 watts to 1250 watts.

2. Power level 3 - 250 watts to 1250 watts or 750 watts to 2800 watts as

programmed by a jumper on the controller circuit board.

3. Power level 4 - 750 watts to 2800 watts.

4. Power level 5 - 750 watts to 2800 watts.

1. Power level 2 - 500 watts to 2500 watts.

2. Power level 3 - 500 watts to 2500 watts or 1500 watts to 5600 watts as

3. Power level 4 - 1500 watts to 5600 watts.

4. Power level 5 - 1500 watts to 5600 watts.

AM-5E

programmed by a jumper on the controller circuit board.

2-29

Page 46

597-1114-11

FIGURE 2-13. TEST EQUIPMENT CONNECTIONS, POWER LEVEL CALIBRATION

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER BEFORE PROCEEDING.

WARNING

2-136. Operate the transmitter rear-door ac on/off control switch to OFF.

2-137. Disconnect the cable from the transmitter modulation monitor connector.

2-138. STEREO ADJUSTMENT. If the transmitter is operated in the stereo mode, the transmitter

stereo circuitry must be adjusted to compensate for antenna system variances. The pri mary objective in the adjustment of the transmitter is to configure the stereo circuitry to minimize distortion and maximize separation across the entire audio band. A proof of per formance sheet is provided at the end of this section to record performance measurements. To adjust the stereo circuitry, perform the following procedures and record the measure ments on the proof of performance sheet at the end of this section.

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER BEFORE PROCEEDING.

WARNING

2-139. Operate the transmitter rear-door ac on/off control switch to OFF.

2-140. Refer to Figure 2-14 and connect the test equipment as shown.

2-30

Page 47

597-1114-12

FIGURE 2-14. TEST EQUIPMENT CONNECTIONS, SEPARATION

2-141. Operate the oscilloscope for: 1) 200 mV/div sensitivity and 2) dc coupled.

2-142. Refer to Figure 2-8 and connect an audio generator to the audio input terminals.

2-143. Operate the transmitter rear-door ac on/off control switch to ON.

2-144. Select the antenna which is configured for equalization circuit 1 operation (refer to STE

REO CIRCUIT BOARD PROGRAMMING in the preceding text if required) and determine a power level.

2-145. Depress the desired power level switch/indicator to illuminate the switch/indicator.

2-146. Refer to SECTION III, OPERATION and perform the following:

1. Operate the stereo circuit board mode control switch to illuminate the stereo indicator. When power is applied to the transmitter, the stereo circuit board will automatically be configured to the stereo mode.

2. Operate the stereo circuit board pilot switch to off.

3. Ensure the equalization circuit 1 indicator on the stereo circuit board is illuminated.

2-147. Adjust equalization circuit 1 as follows:

1. Adjust the audio generator for a 1 KHz left channel output at +10 dBm and observe the lissajous pattern displayed on the oscilloscope.

2-31

Page 48

2. Refer to Figure 2-6 and adjust the left channel level control to obtain a horizontal lissajous pattern (refer to Figure 2-15).

3. Adjust the group delay as follows:

A. Configure the group delay circuitry for adjustment as follows:

1. Refer to Figure 2-6 and configure the left channel 4 microsecond and 8 microsecond sections to in.

2. Refer to Figure 2-6 and operate the left channel delay control fully counterclockwise.

B. Refer to Figure 2-6 and adjust the left channel delay control to close the oscillo-

scope display and obtain a straight-line lissajous display as shown in the maximum left channel separation lissajous pattern (refer to Figure 2-15). If the display will not close, proceed as follows:

1. Refer to Figure 2-6 and: 1) configure only the 8 microsecond delay section to in and 2) adjust the left channel delay control to close the oscilloscope display.

2. If the display will not close refer to Figure 2-6 and: 1) configure only the 4 microsecond delay section to in and 2) adjust the left channel delay control to close the oscilloscope display.

4. Adjust the separation at 7 kHz as follows:

A. Adjust the audio generator for a 7 kHz left channel output at +10 dBm.

B. Refer to Figure 2-6 and adjust the left channel cutoff and peak controls to

obtain a maximum left channel separation lissajous pattern as shown in Figure 2-15.

C. If a maximum left channel lissajous pattern can not be obtained, refer to Figure

2-6 and adjust the left channel delay control to close the oscilloscope display and obtain a straight-line lissajous pattern (refer to Figure 2-15).

5. Repeat the entire procedure for the right channel. Adjust the right channel level, cutoff, peak, and delay controls as required to obtain optimum separation and distortion from the right channel.

6. Repeat the entire procedure for equalization circuit 2. Adjust the equalization circuit 2 using the equalization 2 left/right channel level, cutoff, peak, delay, controls and the equalization 2 group delay sections to obtain optimum separation and distortion.

2-148. Once the stereo adjustment is complete: 1) refer to SECTION III, OPERATION and oper

ate the pilot switch on the stereo circuit board to ON and 2) remove the test equipment.

2-149.

SINGLE CHANNEL LEVEL. The transmitter is equipped with a single channel level con

trol. When the transmitter is operating in the stereo mode, the level control is designed to boost a remaining audio channel level in the event of a failure in one channel. For trans mitters operating in the stereo mode, adjust the single channel level control as follows:

2-32

Page 49

597-0095-19

FIGURE 2-15. EQUALIZATION LISSAJOUS PATTERNS

(2-33/2-34)

Page 50

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER BEFORE PROCEEDING.

WARNING

2-150. Operate the transmitter rear-door ac on/off control switch to OFF.

2-151. If an audio processor is used with the transmitter, ensure the processor is connected as fol

lows:

1. Ensure normal program audio is connected to the processor input.

2. Ensure the audio processor output is connected to the transmitter audio input.

2-152. Operate the transmitter rear-door ac on/off control switch to ON.

2-153. Depress a desired power level switch/indicator to illuminate the switch/indicator.

2-154. Refer to SECTION III, OPERATION and operate the stereo circuit board mode control

switch to illuminate the stereo indicator.

2-155. Disable one channel applied to the transmitter.

2-156. If an audio processor is used with the transmitter, refer to the audio processor manual and

adjust the processor single channel limiter as described in the procedure.

2-157. Refer to SECTION III, OPERATION and operate the stereo circuit board mode control

switch to illuminate the mono left or mono right indicator as determined by the remaining operating audio channel applied to the transmitter.

2-158. Refer to Figure 2-5 and adjust the single channel level control on the exciter circuit board

as required to obtain an approximate 100% modulation indication on the modulation moni tor.

2-35

Page 51

SECTION III

OPERATION

3-1. INTRODUCTION.

3-2. This section identifies all controls and indicators associated with the AM-2.5E/AM-5E

transmitters and provides standard operating procedures.

3-3. CONTROLS AND INDICATORS.

3-4. Figures 3-1, 3-2, and 3-3 present the location of all controls and indicators associated with

normal operation of the AM-2.5E and AM-5E transmitters. Tables 3-1, 3-2, and 3-3 present the functions of each control or indicator. Refer to Figures 3-1 through 3-3 and Tables 3-1 through 3-3 for a description of the controls and indicators associated with the AM-2.5E/AM-5E transmitters.

TABLE 3-1. AM-2.5E/AM-5E CONTROLS AND INDICATORS

(Sheet 1 of 2)

INDEX

NO. NOMENCLATURE FUNCTION

1 FORWARD POWER Displays the transmitter forward power output in

Meter watts as selected by the FORWARD POWER Meter

LOW/HIGH/OFF switch.

2 FORWARD POWER Configures the FORWARD POWER meter: 1) to

Meter HIGH/LOW/OFF display forward power information on the HIGH Switch scale, 2) to display forward power information on the

LOW scale, or 3) to off. In the AM-2.5E: 1) the HIGH scale is from 0 to 3000 watts and 2) the LOW scale is from 0 to 750 watts. In the AM-5E: 1) the HIGH scale is from 0 to 6000 watts and 2) the LOW scale is from 0 to 1500 watts.

3 REFLECTED POWER Displays the transmitter reflected power output in

Meter watts or the ac input voltage in volts as selected by

the REFLECTED POWER HIGH/LOW/VAC Switch.

4 REFLECTED POWER Configures the REFLECTED POWER meter to

Meter HIGH/LOW/VAC display: 1) reflected power information on the HIGH Switch scale, 2) reflected power information on the LOW

scale, or 3) the ac input voltage. In the AM-2.5E:

1) the HIGH scale is from 0 to 300 watts and 2) the LOW scale is from 0 to 60 watts. In the AM-5E:

1) the HIGH scale is from 0 to 600 watts and 2) the LOW scale is from 0 to 150 watts. The ac volts scale is from 150 to 300 volts.

3-1

Page 52

3-2

597-1114-13

FIGURE 3-1. AM-2.5E/AM-5E CONTROLS AND INDICATORS

Page 53

TABLE 3-1. AM-2.5E/AM-5E CONTROLS AND INDICATORS

(Sheet 2 of 2)

INDEX

NO. NOMENCLATURE FUNCTION

5 RF POWER MODULE A modular plug-in assembly containing two RF

power amplifier circuit boards and one modulator circuit board. The AM-2.5E is equipped with 2 power modules. The AM-5E is equipped with 4 power modules. Each power module is designed to output 1375 watts of RF power.

6 POWER BLOCK An RF power amplifier assembly containing two RF

power modules and a combiner unit.

7 LOAD Control Operates in association with the TUNE control to

match the transmitter output impedance to the antenna.

8 TUNE Control Operates in association with the LOAD control to

match the transmitter output impedance to the antenna.

9 AC ON/OFF Controls the application of ac power to the transmit-

Switch ter.

10 Modulation Monitor Calibrates the modulation monitor sample to power

Calibration Controls levels 1 through 5.

11 POWER SUPPLY 1-2 Illuminates to indicate a failure in the 1-2 power

Fault Indicator supply. The supply provides power for RF power (AM-5E Only) modules 1-2.

12 POWER SUPPLY 3-4 Illuminates to indicate a failure in the 3-4 power sup-

Fault Indicator ply. The supply provides power for RF power modules (AM-5E Only) 3-4.

TABLE 3-2. ECU CONTROLS AND INDICATORS

(Sheet 1 of 6)

INDEX

NO. NOMENCLATURE FUNCTION

1 EXCITER Indicator Displays the operating status of the exciter.

GREEN Display - Indicates normal exciter operation. RED Display - Indicates an exciter fault.

3-3

Page 54

TABLE 3-2. ECU CONTROLS AND INDICATORS

(Sheet 2 of 6)

INDEX

NO. NOMENCLATURE FUNCTION

2 POWER MODULES Displays the operating status of the transmitter

Indicator power modules.

GREEN Display - Indicates all power modules are operating normally.

YELLOW Display - Indicates an RF power module is removed from the transmitter.

RED Display - Indicates a fault in an RF power

module.

3 POWER SUPPLY Displays the operating status of the transmitter

Indicator power supply system.

GREEN Display - Indicates normal power supply system operation.

YELLOW DISPLAY - Indicates one or more power supplies are removed from the transmitter.

RED Display - Indicates a power supply system fault.

4 ANTENNA VSWR Displays the condition of the antenna system.

Indicator

GREEN Display - Indicates a normal antenna load.

YELLOW Display - Indicates a VSWR condition

of 1.2 : 1.

RED Display - Indicates a high reflected/forward

power indication. In the AM-2.5E, indicates a 100 watt reflected power condition or a condition which results in a high forward power indication of greater than 20%. In the AM-5E, indicates a 200 watt reflected power condition or a condition which results in a high forward power indication of greater than 20%.

FLASHING RED Display - Indicates a reflected power emergency condition. In the AM-2.5E, indicates a 500 watt reflected power condition. In the AM-5E, indicates a 1000 watt reflected power condition.

3-4

Page 55

TABLE 3-2. ECU CONTROLS AND INDICATORS

(Sheet 3 of 6)

INDEX

NO. NOMENCLATURE FUNCTION

5 POWER CONTROL SWITCHES - A group of five switches designed to

Switch/Indicators select five customer adjustable transmitter operating

output power levels.

In the AM-2.5E, switches 1 and 2 can be adjusted to obtain output power levels from 250 to 1250 watts. Switches 4 and 5 can be adjusted to obtain output power levels from 750 to 2800 watts. Switch 3 is designed to be customer assigned to control power in the 250 to 1250 watt range or the 750 to 2800 watt range.

In the AM-5E, switches 1 and 2 can be adjusted to obtain output power levels from 500 to 2500 watts. Switches 4 and 5 can be adjusted to obtain output power levels from 1500 to 5600 watts. Switch 3 is designed to be customer assigned to control power in the 500 to 2500 watt range or the 1500 to 5600 watt range.

INDICATORS - Illuminates to indicate an associated power control switch has been selected.

6 OFF Switch/Indicator SWITCH - Deenergizes the transmitter RF output

power and configures the unit to off.

INDICATOR - Illuminates to indicate the OFF switch has been selected.

7 POWER Switch/ SWITCH - Instructs the system controller to raise

Indicator the transmitter output power. The switch is designed

with the ability to raise power from 10% to 15% of the selected output power level.

INDICATOR - During manual operating conditions, illuminates to indicate the POWER switch is selected. During automatic raise conditions, the indicator will illuminate to indicate the rate of automatic power increase.

8 POWER Switch/ SWITCH - Instructs the system controller to lower

Indicator the transmitter output power. The switch is designed

with the ability to lower power from 10% to 15% of the selected output power level.

INDICATOR - During manual operating conditions, illuminates to indicate the POWER switch is selected. During automatic lower conditions, the indicator will illuminate to indicate the rate of automatic power decrease.

3-5

Page 56

TABLE 3-2. ECU CONTROLS AND INDICATORS

(Sheet 4 of 6)

INDEX

NO. NOMENCLATURE FUNCTION

9 RESET Switch/ SWITCH - Clears the transmitter fault circuitry

Indicator when: 1) the switch is depressed and 2) if the fault

condition is removed.

INDICATOR - Illuminates to indicate a fault has been encountered.

10 EXCITER MONITOR Illuminates to indicate the exciter is configured

STEREO Indicator to the stereo mode.

11 EXCITER MONITOR SWITCH - Selects either left/right channel or

MODE Switch/ L-R/L+R information for presentation on the Indicator EXCITER MONITOR LED bar-graph display.

INDICATOR - Indicates the type of information selected for display on the exciter monitor. The L/R indicator will illuminate to indicate the display of left/right channel information. The L+R/L-R indi- cator will illuminate to indicate the display of L+R/ L-R information.

12 EXCITER MONITOR SWITCH - Selects either positive or negative peak

+/- POLARITY audio for application to the EXCITER MONITOR Switch/Indicator LED bar-graph display.

INDICATOR - Indicates the signal polarity selected for display on the exciter monitor. The + indicator will illuminate to indicate the display of positive information. The - indicator will illuminate to indicate the display of negative information.

13 EXCITER MONITOR Displays left, right, L+R, or L-R audio channel

LED Bar-Graph Display peak levels as selected by the EXCITER MONITOR

MODE and POLARITY switches. Each indicator will illuminate at the level indicated on the display. In addition, the display is equipped with an autorange feature to allow the monitoring of signals in the 0.5% to 14.5% range. Indications of autorange operation are provided by the R/L-R and L/L+R X10 indicators.

14 EXCITER MONITOR Illuminates to indicate the exciter is configured to the

MONO Indicator mono L, mono R, or mono L+R mode of operation.

15 R/L-R Display Illuminates to indicate the autorange feature is

X10 Indicator enabled to expand the R/L-R display by 10 to provide

the resolution required for low level audio monitoring.

3-6

Page 57

597-1114-23

FIGURE 3-2. ECU CONTROLS AND INDICATORS

(3-7/3-8)

Page 58

TABLE 3-2. ECU CONTROLS AND INDICATORS

(Sheet 5 of 6)

INDEX

NO. NOMENCLATURE FUNCTION

16 L/L+R Display Illuminates to indicate the autorange feature is

X10 Indicator enabled to expand the L/L+R display by 10 to provide

the resolution required for low level audio monitoring.

17 OVERTEMP Indicator Illuminates to indicate when the transmitter

operating temperature exceeds 70° C (158° F).

18 FOLDBACK Indicator Illuminates to indicate when the transmitter is in a

foldback condition. Foldback is when the transmitter output power is automatically reduced in response to one of the following fault conditions: 1) high reflected power, 2) high forward power, 3) high temperature, or

4) detection of a lightning potential.

19 INTERLOCK Illuminates to indicate the internal interlock, external

Indicator interlock, and the remote fail-safe are closed. The

remote control fail-safe must be closed only when the transmitter is configured for remote control operation.

20 REMOTE Indicator Illuminates to indicate transmitter remote control

operations are enabled.

21 CONFLICT Indicator Illuminates to indicate an incorrect power level is

selected for operation into the antenna connected to the transmitter.

22 LIGHTNING Indicator In the AM-2.5E, illuminates to indicate a 1500 volt or

greater potential is present at the transmitter output. In the AM-5E, illuminates to indicate a 2100 volt or greater potential is present at the transmitter output.

23 PWM Mute Indicator Illuminates to indicate the power control PWM signal

is muted in response to a fault such as lightning, an exciter fault, a reflected power emergency, an open remote control fail-safe, or an external transmitter mute.

24 Remote Fail-safe Illuminates to indicate the remote control unit is

Indicator enabled.

25 Remote/Local Controls the transmitter remote control operations.

Switch When the switch is operated to remote, remote control

operations are enabled. When the switch is operated to local, remote control operations are disabled.

3-9

Page 59

TABLE 3-2. ECU CONTROLS AND INDICATORS

(Sheet 6 of 6)

INDEX

NO. NOMENCLATURE FUNCTION

26 Battery OK Indicator When the battery test switch is depressed, the indi-

cator will: 1) illuminate to indicate the battery is operational or 2) not illuminate to indicate the battery is to be replaced.

27 Battery Test Switch When depressed, evaluates the controller battery

status. The status is displayed by the battery OK indicator.

28 Pilot On/Off Switch Enables and disables the stereo pilot signal.

29 Stereo Indicator Illuminates to indicate the exciter is configured to the

stereo mode.

30 Mono L+R Indicator Illuminates to indicate the exciter is configured to the

mono L+R mode.

31 Mono Right Indicator Illuminates to indicate the exciter is configured to the

mono right mode.

32 Mono Left Indicator Illuminates to indicate the exciter is configured to the

mono left mode.

33 Exciter Mode Configures the exciter for stereo, mono L+R, mono

Control Switch left, or mono right operation. The switch is designed

to configure the exciter to a different mode of operation each time the switch is depressed. The switch will advance to a mode of operation in the following order: 1) mono left, 2) mono right, 3) mono L+R, and

4) stereo.

34 Stereo Equalization 1 Illuminates to indicate the exciter stereo equalization

Indicator 1 circuit is active.

35 Stereo Equalization 2 Illuminates to indicate the exciter stereo equalization

Indicator 2 circuit is active.

36 Lock Indicator Illuminates to indicate the exciter is locked to the

programmed carrier frequency.

37 Exciter +5V Indicator Illuminates to indicate the ECU +5V supply is

operational.

38 Exciter +15V Indicator Illuminates to indicate the ECU +15V supply is

operational.

39 Exciter -15V Indicator Illuminates to indicate the ECU -15V supply is

operational.

40 Negative Limiter Illuminates to indicate the negative limiter circuit is

Indicator enabled. Factory adjusted to illuminate at

approximately 94% negative modulation.

3-10

Page 60

TABLE 3-3. POWER MODULE CONTROLS AND INDICATORS

(Sheet 1 of 2)

INDEX

NO. NOMENCLATURE FUNCTION

1 PA 1 RF DRIVE Illuminates to indicate RF drive is present at

Indicator power amplifier 1.

2 PA 1 FAULT Illuminates to indicate a fault has occurred

Indicator in power amplifier 1.

3 PA 2 RF DRIVE Illuminates to indicate RF drive is present at

Indicator power amplifier 2.

4 PA 2 FAULT Illuminates to indicate a fault has occurred in

Indicator power amplifier 2.

5 MOD PWM DRIVE Illuminates to indicate the exciter PWM drive

Indicator is present at the modulator circuit board.

6 MOD POWER Illuminates to indicate dc power is present at the

Indicator modulator circuit board.

FIGURE 3-3. POWER MODULE CONTROLS AND INDICATORS

597-1112-31

3-11

Page 61

TABLE 3-3. POWER MODULE CONTROLS AND INDICATORS

(Sheet 2 of 2)

INDEX

NO. NOMENCLATURE FUNCTION

7 MOD FAULT Illuminates to indicate a fault has occurred in the

Indicator modulator circuit board.

8 MOD FUSE Illuminates to indicate the modulator circuit

Indicator board fuse has blown.

9 MOD SAMPLE Provides a dc voltage sample of the modulator circuit

board output. In the AM-2.5E, the sample will be equal to approximately 5.6 volts dc at 2.5 kW (refer to factory test data sheets). In the AM-5E, the sample will be equal to approximately 5.6 volts dc at 5 kW (refer to factory test data sheets).

3-5. OPERATION.

CAUTION

WHEN AC POWER IS APPLIED TO THE TRANSMIT TER AND THE RF DRIVE AND PWM DRIVE INDICA

CAUTION

TORS ON RF POWER MODULES IN A POWER BLOCK ARE EXTINGUISHED, THE RF POWER MODULES MUST BE REMOVED FROM THE TRANSMITTER CHASSIS TO PREVENT DAMAGE TO THE MODULES.

NOTE

ENSURE THE TRANSMITTER IS COMPLETELY INSTALLED PRIOR TO PERFORMING THE FOLLOW

NOTE

3-6. TURN-ON.

3-7. Operate the transmitter to ON by performing the following procedure.

3-8. Ensure the transmitter rear-panel ac on/off switch is operated to ON. The ECU and RF

power module front-panel indicators will illuminate.

3-9. Observe the ECU and RF power module indicators. Ensure normal operating conditions

are displayed by all indicators. If an indicator displays a fault condition, operate the ac power switch to off and refer to SECTION V, MAINTENANCE to locate the problem.

3-10. Select an output power level by depressing the desired power level switch/indicator. The

following events will occur:

ING PROCEDURES.

1. The power level switch indicator will illuminate.

2. The transmitter flushing fans will begin operation.

3. The transmitter output power will be displayed on the FORWARD and REFLECTED power meters.

3-12

Page 62

3-11. Operate the FORWARD and REFLECTED power meters to observe the transmitter for

ward and reflected power indications.

3-12. Adjust the transmitter output power if required by performing the POWER ADJUST

procedure presented in the following text.

3-13. If remote control operation is desired, operate the local/remote switch on the controller cir

cuit board to remote. This will enable both local and remote operation.

3-14.

3-15. Operate the transmitter to OFF by depressing the OFF switch/indicator to illuminate the

3-16. METERING.

3-17. FORWARD POWER. The forward power meter presents forward power indications. To

3-18.

TURN OFF.

switch/indicator. The transmitter will operate to off.

operate the meter, proceed as follows:

1. To monitor low forward power levels, operate the FORWARD POWER meter switch to LOW. In the AM-2.5E, the LOW scale is from 0 to 300 watts. In the AM-5E, the LOW scale is from 0 to 1500 watts.

2. To monitor high forward power levels, operate the FORWARD POWER meter switch to HIGH. In the AM-2.5E, the HIGH scale is from 0 to 3000 watts. In the AM-5E, the HIGH scale is from 0 to 6000 watts.

3. To configure the FORWARD POWER meter to off, operate FORWARD POWER meter switch to OFF.

REFLECTED POWER. The reflected power meter presents reflected power and ac input

indications. To operate the meter, proceed as follows:

1. To monitor low reflected power levels, operate the REFLECTED POWER meter switch to LOW. In the AM-2.5E, the LOW scale is from 0 to 60 watts. In the AM-5E, the LOW scale is from 0 to 150 watts.

2. To monitor high reflected power levels, operate the REFLECTED POWER meter switch to HIGH. In the AM-2.5E, the HIGH scale is from 0 to 300 watts. In the AM-5E, the HIGH scale is from 0 to 600 watts.

3. To monitor the ac input voltage, operate the REFLECTED POWER meter switch to VAC.

3-19.

3-20. The POWER and switches adjust the transmitter output power. To adjust the trans

POWER ADJUST.

mitter power, proceed as follows:

1. Depress the POWER switch to increase the transmitter output power. Observe the transmitter output power indications on the FORWARD and REFLECTED power meters.

The switch will increase power from 10% to 15% of the selected power level.

2. Depress the POWER the transmitter output power indications on the FORWARD and REFLECTED power meters.

The switch will decrease power from 10% to 15% of the selected power level.

switch to decrease the transmitter output power. Observe

3-13

Page 63

3-21. MONO/STEREO OPERATION.

3-22. To configure the transmitter for monophonic or stereophonic operation, perform the follow

ing procedures.

3-23.

3-24.

3-25. Mono Operation - Stereo Circuit Board. To configure the transmitter for mono operation

3-26. Mono Operation - No Stereo Circuit Board. In the event of a stereo circuit board failure,

STEREO OPERATION. To configure the transmitter for stereo operations, depress the ex

citer mode control switch to illuminate the stereo indicator on the stereo circuit board. In addition, the ECU front-panel stereo indicator will illuminate.

MONO OPERATION. The transmitter can be configured to the monophonic mode by:

1) manually selecting the desired mono mode using the stereo circuit board or 2) automati cally configuring the transmitter by removing the stereo circuit board. To configure the transmitter for mono operations, proceed as follows:

using the stereo circuit board, depress the exciter mode control switch to illuminate the mono L+R, mono left, or mono right indicators on the stereo circuit board. In addition, the ECU front-panel MONO indicator will illuminate.

the transmitter will automatically configure to the monophonic mode when the stereo cir cuit board is removed from the ECU. To remove the stereo circuit board and configure the transmitter for monophonic operation, proceed as follows:

CAUTION

TO PREVENT DAMAGE TO THE TRANSMITTER, EN SURE THE TRANSMITTER PRIMARY POWER IS OPER

CAUTION

ATED TO OFF BEFORE REMOVING THE STEREO CIR CUIT BOARD.

1. Operate the transmitter primary power to off.

2. Completely remove the stereo circuit board from the ECU. Do not leave the circuit board in the ECU chassis.

3. Refer to Figure 2-5 in SECTION II, INSTALLATION and ensure the monophonic audio channel select jumper is configured for the desired audio channel.

4. If required, adjust the single channel level by referring to SECTION II, INSTALLATION and performing the SINGLE CHANNEL LEVEL procedure.

3-27. PILOT CONTROL.

3-28. The pilot switch on the stereo circuit board controls the pilot tone. Operate the pilot switch

to on to enable the pilot tone. Operate the pilot switch to off to disable the pilot tone.

3-29.

3-30. The following text presents procedures for specific exciter monitoring functions. Perform

3-31. MONO/STEREO INDICATIONS. The MONO and STEREO indicators display the oper

3-32.

EXCITER MONITOR OPERATION.

the appropriate procedure for the type of monitor function desired.

ating mode of the exciter. The MONO indicator will illuminate to indicate when the excit er is configured for mono L+R, mono left, or mono right operation. The STEREO indicator will illuminate to indicate when the exciter is configured for stereo operation.

INPUT SELECTION. Depress the L/R/L+R/L-R MODE switch/indicator to: 1) illuminate

the L/R indicator to select left and right channel information or 2) illuminate the L+R/L-R indicator to select L+R and L-R information. The selected parameter will appear on the EXCITER MONITOR display.

3-14

Page 64

3-33. POLARITY SELECTION. Depress the POLARITY switch/indicator to: 1) illuminate the +

indicator to select positive peak audio or 2) illuminate the - indicator to select negative peak audio. The selected parameter will appear on the EXCITER MONITOR display.

3-34. X10 AUTORANGE INDICATIONS. The EXCITER MONITOR display is designed with

an autorange function to provide the appropriate resolution for the applied signal level. The L/L+R display X10 indicator will illuminate to indicate the display is expanded by 10. The R/L-R display X10 indicator will illuminate to indicate the display is expanded by 10.

3-35.

3-36. The transmitter monitors several parameters for fault conditions. The RESET indicator

FAULT RESET.

will illuminate to indicate a fault when one of the following conditions occur:

1) over-temperature, 2) exciter fault, 3) power supply fault, 4) RF power module fault,

5) high reflected/forward power, 6) reflected power emergency, or 7) lightning. Once the fault condition is removed, the fault circuitry must be reset. If a power supply fault is en countered, the transmitter AC power must be disconnected to remove the fault condition (refer to POWER SUPPLY FAULT RESET in the following text). To reset the fault cir cuitry, depress the RESET switch. The fault circuitry will be reset.

3-37.

3-38. If a power supply fault is encountered, ac power must be disconnected from the transmitter

3-39.

3-40. The transmitter controller is equipped with an on/off cycle counter circuit. The circuit is

3-41.

3-42. The transmitter is protected from modulation levels above 150% by an over-modulation

3-43.

3-44. The TRANSMITTER MONITOR is designed to present the operating status of: 1) the

POWER SUPPLY FAULT RESET.

to clear the fault. To reset a power supply fault, proceed as follows:

1. Operate the rear-door ac ON/OFF switch to off.

2. Operate the rear-door ac on/off switch to on.

3. Depress the RESET switch.

OVER-CYCLE OFF.

designed to monitor transmitter on/off cycles. If the transmitter is operated on/off seven times within 15 seconds, the transmitter will automatically operate to OFF. The power level or OFF switch/indicators will not respond. To operate the transmitter to ON, proceed as follows:

1. Do not depress any power level switch/indicators or the OFF switch/indicator for approximately 30 seconds. This allows the circuit to reset.

2. Depress the desired power level switch/indicator.

OVER-MODULATION PWM MUTE.

circuit. If the transmitter modulation increases to a level above 150%, the PWM signal will be muted. This will mute the output power and prevent damage to the transmitter power supply modules.

TRANSMITTER MONITOR.

exciter, 2) the RF power modules, 3) the power supply, 4) the antenna, 5) the remote con trol, 6) antenna conflict conditions, 7) lightning conditions, 8) interlocks, 9) foldback condi tions, and 10) over-temperature conditions. Use the information presented in Table 3-2 to determine the status of the transmitter components and operating conditions.

3-45.

3-46. The battery test and battery OK indicator check the ECU battery backup system. To check

BATTERY TEST.

the ECU battery, depress the battery test switch. The battery OK indicator will illuminate to indicate an acceptable battery voltage. If the battery OK indicator does not illuminate, replace the battery.

3-15

Page 65

3-47. CONTROLLER PWM MUTE INDICATOR.

3-48. The PWM mute indicator illuminates to indicate when the power control PWM signal is

muted. The power control PWM signal is muted during: 1) lightning conditions, 2) an ex citer fault, 3) reflected power emergency conditions, 4) an open remote control fail-safe, or

5) a transmitter mute control signal.

3-49.

3-50. The controller remote fail-safe indicator illuminates to indicate the remote control unit is

3-51. EXCITER LOCK INDICATOR.

3-52. The exciter circuit board lock indicator illuminates to indicate when the exciter is locked to

3-53.

3-54. The exciter circuit board +5V, +15V, and -15V indicators display the status of the operating

3-55. STEREO EQUALIZATION INDICATORS.

3-56. The stereo circuit board equalization 1 indicator illuminates to indicate when equalization

3-57. RF POWER MODULE INDICATORS.

3-58. The RF power module indicators are designed to present the operating status of the power

CONTROLLER REMOTE FAIL-SAFE INDICATOR.

enabled. The indicator will extinguish when the remote control unit is disabled.

the programmed carrier frequency. The indicator will extinguish when the exciter is un locked from the programmed carrier frequency.

EXCITER +5V/+15V/-15V INDICATORS.

potentials from the ECU power supply. The +5V, +15V, and -15V indicators will illuminate to indicate the +5 volt, +15 volt, and -15 supplies are operational.

circuit 1 is selected. The stereo circuit board equalization 2 indicator illuminates to indi cate when equalization circuit 2 is selected.

amplifier circuit boards and the modulator circuit board. Use the information presented in Table 3-3 to determine the status of the power amplifier circuit boards and the modulator circuit board.

3-59.

3-60. On AM-5E models, the power supply indicators on the transmitter lower front-panel are

3-61.

3-62. The exciter circuit board negative limiter indicator displays the status of the exciter nega

3-63. HIGH/LOW AC LINE CONDITIONS.

3-64. The transmitter is equipped with an ac line monitor. The monitor will deenergize the

POWER SUPPLY INDICATORS.

designed to present the operating status of the power supply circuit boards. The AM-5E transmitter is equipped with power supply 1-2 and 3-4. The indicators illuminate to indi cate a failure in a power supply.

EXCITER NEGATIVE LIMITER INDICATOR.

tive limiter circuit. The indicator will illuminate to indicate the negative limiter circuit is enabled. The indicator is factory adjusted to illuminate at approximately 94% negative modulation.

transmitter in the event the ac power line is below 190 Volts or above 260 Volts. If this condition occurs: 1) the transmitter output power will be disabled and 2) a no fault or emergency condition will be generated. The transmitter will re-energize when the high/ low ac line condition is removed.

3-16

Page 66

SECTION IV

THEORY OF OPERATION

4-1. INTRODUCTION.

4-2. This section presents the theory of operation for the Broadcast Electronics

AM-2.5E/AM-5E transmitters.

4-3. The following text presents the AM-2.5E/AM-5E transmitter overall theory of operation.

The transmitter is divided into modular components for the discussion. The modular components consist of the: 1) exciter/control unit (ECU), 2) output network, 3) RF power module, 4) RF combiner, and 5) power supply. The ECU, RF power module, and power supply are presented in further detail by the publication sections at the end of this manual.

4-4. Figures 4-1 and 4-2 present the AM-2.5E and AM-5E block diagrams. Figure 4-1

presents the AM-2.5E block diagram. Refer to Figure 4-1 and the AM-2.5E overall schematic diagram in SECTION VII as required for the following discussion. Figure 4-2 presents the AM-5E block diagram. Refer to Figure 4-2 and the AM-5E overall schematic diagram in SECTION VII as required for the following discussion.

4-5.

4-6. ECU.

4-7. GENERAL. The transmitter ECU (exciter/control unit) is a modular assembly containing

4-8.

4-9. The stereo circuit board is equipped with four modes of operation: 1) mono left, 2) mono

4-10. The stereo circuit board operates in association with the ECU exciter circuit board to

FUNCTIONAL DESCRIPTION.

plug-in stereo, exciter, controller, and extender circuit board assemblies. A forward power meter is provided to monitor the transmitter forward output power. A reflected power/primary ac power meter provides reflected power and primary ac voltage indications. The ECU switch and display circuitry is contained on switch and display circuit boards. Power for the ECU is provided by a modular switching power supply unit.

STEREO CIRCUIT BOARD. The ECU stereo circuit board consists of C-QUAM AM stereo

circuitry. C-QUAM AM stereo is a mode of AM stereo transmission utilizing amplitude modulated (L+R) information and independently quadrature modulated stereo (L-R) information. The results produce a stereo transmission system compatible with mono receivers.

right, 3) mono L+R, and 4) stereo. Configuring the circuit board to monophonic operation is accomplished by: 1) operating the circuit board to the mono left, mono right, or mono L+R mode or 2) removing the stereo circuit board. The circuit board is equipped with two equalization circuits. The circuits allow the transmitter to be configured for two different antenna patterns such as for a day pattern and a night pattern.

provide RF drive to the RF power modules. The stereo circuit board receives left and right channel audio and an unmodulated TTL level RF signal at 4 times the carrier frequency from the exciter circuit board. The stereo circuit board outputs a TTL level RF signal to the exciter circuit board.

4-11. EXCITER CIRCUIT BOARD. The ECU exciter circuit board is a modular plug-in exciter

assembly. The circuit board operates in association with the stereo circuit board to produce a C-QUAM AM stereo RF output. Instrumentation amplifiers provide balanced left and right channel transformerless audio inputs.

4-1

Page 67

4-12. The exciter circuit board generates: 1) a PWM (pulse-width-modulation) signal and 2) an

RF carrier frequency signal. The 122 kHz to 135 kHz PWM signal is routed for application to the modulator circuit boards in the RF power modules. The RF carrier frequency signal is applied to the power amplifier circuit boards in the RF power modules. The exciter carrier frequency is established by a digital frequency synthesizer. The synthesizer is a phase-locked-loop circuit which provides extremely accurate and reliable carrier frequency operation.

4-13.

4-14. The controller circuit board is designed with two interlock circuits. A transmitter

4-15. The transmitter power is controlled by a power control circuit. The circuit allows the

4-16. Several monitoring and display circuits provide information on transmitter operating

4-17. Additional display circuits include: 1) remote, 2) conflict, 3) lightning, 4) interlock,

CONTROLLER CIRCUIT BOARD. All transmitter control operations are directed by the

ECU controller circuit board. The controller circuit board is designed with CMOS control and monitoring circuitry.

external interlock is provided such as for a test load. An antenna interlock circuit is provided to prevent the transmitter from operating into an incorrect antenna.

transmitter to be operated at five power levels. A power trim circuit allows the transmitter power to be increased or decreased as required. A high reflected power detection circuit, a high forward power detection circuit, and a high temperature detection circuit operate in association with the power control circuit to foldback the transmitter power during high reflected power, high forward power, and high temperature conditions. In addition, a lightning detector circuit is provided to mute the transmitter when lightning is present at the antenna.

conditions. An RF power module status circuit displays: 1) if a module is removed for maintenance or 2) if a power module fault has occurred. A power supply status circuit displays: 1) if a power supply circuit board is removed for maintenance or 2) if a power supply fault has occurred. An exciter status circuit indicates if a fault has occurred in the exciter. An antenna status circuit displays: 1) 1.2 : 1 VSWR conditions, 2) high reflected power conditions, and 3) emergency reflected power conditions.

5) over-temperature, and 6) reset. A remote indicator displays the status of the remote control system. A conflict indicator illuminates to indicate an incorrect power level is selected for operation into an antenna. A lightning indicator illuminates to indicate the presence of lightning at the transmitter output. An interlock indicator displays the status of the internal and external interlock. An over-temperature indicator illuminates to indicate a transmitter temperature greater than 70 degrees C. A reset indicator illuminates to indicate a transmitter fault has occurred. Transmitter faults include:

1) exciter failure, 2) power supply failure, 3) RF power module failure, 4) high reflected power conditions, 5) reflected power emergency conditions, 6) over-temperature conditions, 7) lightning conditions, and 8) 1.2:1 VSWR conditions.

4-18.

4-19. RF POWER MODULE.

4-20. An RF power module is a plug-in assembly containing two RF amplifier circuit boards

POWER SUPPLY. DC operating potentials for the ECU assembly is provided by a modular

switching power supply unit. The unit provides +5V, +15V, and -15V dc operating potentials for the ECU circuit boards. +5V, +15V, and -15V indicators are provided on the exciter circuit board.

and a modulator circuit board. Each RF power module is designed to produce 1375 watts of RF power. Two RF power modules are contained in a power block. The AM-2.5E transmitter is equipped with 1 power block. The AM-5E transmitter is equipped with 2 power blocks.

4-2

Page 68

597-1114-5

FIGURE 4-1. AM-2.5E BLOCK DIAGRAM

(4-3/4-4)

Page 69

597-1114-4

FIGURE 4-2. AM-5E BLOCK DIAGRAM

(4-5/4-6)

Page 70

4-21. The modular design of the RF power modules allow the modules to be removed from the

transmitter for maintenance. The remaining power modules will provide power to maintain on-air operation.

4-22. The PWM signal from the exciter circuit board is applied to the modulator circuit board.

The modulator circuit board is designed to amplify and convert the PWM signal to a dc voltage which varies at an audio rate. The output of the modulator circuit board is applied to the RF amplifier circuit boards. Four indicator circuits monitor and display the status of the: 1) PWM drive signal, 2) B+ dc supply, 3) modulator fault conditions, and

4) blown fuse conditions.

4-23. The RF amplifier circuit boards are designed with Class E amplifier technology and

MOSFET power transistors. The circuit board operates from: 1) the varying dc voltage from the modulator circuit board and 2) the RF drive signal from the exciter circuit board. The RF drive signal from the exciter circuit board and the varying dc voltage from the modulator are applied to a push-pull power MOSFET transistor amplifier circuit. The amplifier circuit is designed to output approximately 687.5 watts of RF power. A fault detection circuit monitors amplifier operation for fault conditions.

4-24.

4-25. Power from each RF amplifier circuit board is applied to a star combiner network. The

4-26. In addition to combining the RF power from the RF power modules, the combiner design

4-27.

4-28. The output network is a modular assembly designed to match the transmitter impedance

4-29. The bandpass filter is an eight element LC filter designed to attenuate all harmonic

RF COMBINER.

combiner components are located on the rear panel of each power block. The star combiner network consists of individual transformer and inductor networks for each amplifier circuit board. The combiner accepts RF power from each RF power module to produce the rated RF output power.

allows one or more RF power modules to be removed from the transmitter for maintenance. The remaining RF power modules will continue to operate to maintain on-air operation. This is accomplished without the use of dummy modules or bypass switches.

OUTPUT NETWORK.

to the antenna. The assembly consists of a: 1) bandpass filter, 2) directional coupler circuit board, 3) T-matching network, 4) lightning protection circuit board, and 5) a lightning detection circuit board.

frequencies to FCC, DOC, and CCIR levels. The directional coupler circuit board consists of a circuit designed to sample the transmitter RF output. The circuit board generates both forward and reflected power samples for application to the controller circuit board. The T" matching network consists of an LC network. The network is designed to match the transmitter impedance to the antenna.

4-30. A lightning protection circuit board is provided to protect the transmitter circuitry from

direct lightning potentials. The circuit protects the transmitter by shunting lightning potentials to ground. The lightning detector circuit board is designed to mute the transmitter RF output during the presence of a lightning potential. The lightning detector circuit board is controlled by a spark gap. The circuit will respond to potentials of 1500 volts in AM-2.5E models and 2100 volts in AM-5E models. This prevents the transmitter from muting during near-by lightning activity.

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4-31. POWER SUPPLY.

4-32. A single phase source of 196 to 252 volts ac 50/60 Hz is required to operate the

transmitter. The power source is routed through an RFI filter to prevent the coupling of RFI components into or out-of the transmitter. A rear-door ac on/off switch provides ac power control and disconnects all ac power to the transmitter when the door is opened. The ac line is monitored for high/low conditions by an ac line voltage monitor. The transmitter primary ac power will be interrupted if the ac line is above 260 volts or below 195 volts. Primary fuses protect the transmitter from over-current conditions. A power factor corrector circuit modifies the ac line impedance to provide a power factor of approximately 0.9.

4-33. The ac line voltage is sampled at the ac sample circuit board. The sample circuit board

provides an ac line voltage sample for application to the meter switch circuit board.

4-34.

POWER SUPPLY CIRCUIT BOARD. DC operating potentials for the RF power modules

are provided by power supply circuit boards. One power supply circuit board provides dc operating potentials for one power block. The AM-2.5E transmitter is equipped with 1 power supply circuit board. The AM-5E transmitter is equipped with 2 power supply circuit boards.

4-35. The power supply circuit board consists of a: 1) switching power supply circuit,

2) conventional bridge rectifier circuit, 3) fault detection circuit. The switching power supply circuit operates directly from the ac power source. No primary ac power transformer is included in the circuit. An SCR controlled bridge rectifier circuit and a switching regulator circuit converts ac potentials to dc potentials at a desired voltage. Control of the dc output voltage is provided by a power control PWM signal from the controller.

4-36. A transformer with five secondary windings provide low-voltage ac potentials to five

full-wave bridge rectifiers circuits. The circuits provide dc operating potentials for the power supply circuit board and RF power module circuitry.

4-37. The power supply design provides the RF power modules with a constant and stable dc

operating supply by not responding to fluctuations or surges in the ac line voltage. The supply will produce a constant dc voltage during high/low ac line voltage or surge conditions.

4-38. The switching power supply output voltage is controlled by a power control PWM signal

from the controller circuit board. Current reduction at turn-on is controlled by a soft-start circuit. The circuit is designed to generate start pulses synchronized to the ac line phase to slowly bias the SCR bridge rectifier circuit on during initial turn-on operations. The switching regulator circuitry is monitored for proper operation by an overvoltage and loss-of-PWM signal circuitry. The switching regulator operation is performed by IGBT (insulated-gate-bi-polar-transistors) transistors. The IGBTs are designed to provide extremely reliable and efficient operation.

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4-39. METERING.

4-40. The transmitter metering consists of the forward power meter, reflected power/primary ac

input voltage meter, and the exciter modulation meter. Forward power information is presented on the forward power meter. Reflected power/primary ac input voltage information is presented on the reflected power/primary ac input voltage meter. The meters are controlled by three-position switches. Forward and reflected power samples for the metering circuitry are provided by the directional coupler circuit board. An ac sample for the reflected power/primary ac input voltage meter is provided by an ac sample circuit board.

4-41. Monitoring of exciter operations is provided by the exciter modulation monitor. Two 30

segment multi-color bar graph displays present L/L+R and R/L-R information. A X10 mode allows the monitoring of low level signals such as the pilot tone.

4-42.

4-43. The AM-2.5E/AM-5E transmitters are equipped with 2 cooling fans. The fans are

4-44. INTERFACE CIRCUIT BOARD (AM-5E ONLY).

4-45. On AM-5E models, communication between the controller, RF power modules, and the

4-46.

4-47. POWER SUPPLIES.

4-48. The AM-2.5E/AM-5E transmitters require a 196V to 252V ac single phase power source

COOLING FANS.

controlled by an optically-coupled-relay. In the fans provide 500 CFM of cooling air for the transmitter. A temperature sensor circuit board monitors the transmitter air temperature and provides status information to the controller.

power supply circuit boards is provided by an interface circuit board. The circuit board:

1) routes status information from the RF power modules and power supply circuit boards to the controller and 2) routes control signals from the controller to the RF power modules and the power supply circuit boards.

DETAILED DESCRIPTION.

(refer to Figure 4-3). The following text presents ac power source required for each transmitter.

TRANSMITTER AC POWER SOURCE

AM-2.5E 196V to 252V ac 50/60 Hz single phase at 75 Amperes.

AM-5E 196V to 252V ac 50/60 Hz single phase at 125 Amperes.

4-49. AC INPUT CIRCUITRY.

4-50. When the transmitter fused disconnect is closed, single phase ac power is routed through

an RFI filter to rear-door ac input switch S1. The filter prevents the coupling of RFI components into or out-of the transmitter. S1 is the transmitter primary ac power safety device. S1 disconnects primary ac power when the transmitter rear door is opened.

4-51. The ac line is monitored for high/low conditions by an ac line voltage monitor. The

monitor controls ac power contactor K2. The transmitter primary ac power will be interrupted if the ac line is above 260 volts or below 190 volts. Overload protection for the transmitter is provided by fuses F1 and F2.

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4-52. A power factor corrector circuit consisting of inductors L3/L4 and capacitor C1 modifies

the ac line impedance to provide a power factor of approximately 0.9. C1 is switched into the circuit during soft-start by the power factor corrector relay circuit board. The relay circuit board is controlled by a circuit on the power supply circuit board. Metal-Oxide-Varistors MOV1, MOV2, and MOV3 protect the transmitter power supply circuitry from ac line voltage surge potentials. AC power from the MOVs is applied to the following circuits: 1) the ECU power supply assembly, 2) the transmitter flushing fans, 3) low voltage power supply transformer T1, 4) the power supply circuit board, and

5) the ac sample circuit board.

4-53.

4-54. The ECU power supply is a 40W modular switching power supply unit. The power supply

4-55. The power supply for the ECU controller circuit board is backed-up by a 9V battery.

4-56. The battery back-up system requires a standard 9V battery. The battery will maintain

4-57.

4-58. Cooling air for the transmitter circuitry is provided by flushing fans B1 and B2. Control

4-59. The flushing fans are controlled by a signal from the ECU controller circuit board. When

ECU POWER SUPPLY ASSEMBLY.

assembly provides regulated +5V, +15V, and -15V operating potentials for the ECU circuit boards.

During an ac power failure, the battery will maintain the transmitter operating configuration stored in the controller logic circuitry. Once power is returned to the transmitter, the transmitter will automatically resume operation in the configuration appearing prior to the ac failure. If an extended ac power failure occurs, the transmitter will be operated to off by an ac loss/auto shutdown circuit.

the controller logic for several months. Replace the battery approximately once a year to ensure proper transmitter operation during ac power failure conditions.

TRANSMITTER FLUSHING FANS.

of the fans is provided by optically-coupled-relay (OCR) K1.

a power level switch/indicator is depressed, the controller circuit board will enable optically-coupled relay (OCR) K1 to energize the fans. The fans will operate during transmitter operation.

4-60.

4-61. Low-voltage operating potentials for the transmitter power supply circuit board and RF

4-62.

4-63. Low and high voltage dc operating potentials for the RF power modules are provided by

4-64. The power supply circuit board is equipped with: 1) a switching power supply circuit

LOW-VOLTAGE POWER SUPPLY TRANSFORMER.

power modules are provided by ac power transformer T1. Transformer T1 consists of:

1) one primary winding and 2) five secondary windings. The secondary windings provide low-voltage ac potentials for application to five rectifier circuits on the power supply circuit board. The circuitry provides dc operating potentials for the power supply and the RF power modules.

POWER SUPPLY CIRCUIT BOARD.

the power supply circuit board. The AM-2.5E is equipped with 1 power supply circuit board. The AM-5E is equipped with 2 power supply circuit boards. Each power supply circuit board provides dc operating potentials for two RF power modules.

designed to produce high-voltage operating potentials and 2) conventional rectifier circuitry designed to produce low-voltage operating potentials. The following text describes the circuitry.

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597-1114-6

FIGURE 4-3. AM-2.5E/AM-5E POWER SUPPLY SIMPLIFIED SCHEMATIC

(4-11/4-12)

Page 75

4-65. CONVENTIONAL RECTIFIER CIRCUITRY. +30V and +20V dc operating potentials for the

RF power modules are provided by four conventional rectifier circuits. AC power from a winding of ac power transformer T1 is applied to bridge rectifier D9. D9 rectifies the ac potential into an unregulated +20 volt ac supply for application to: 1) the modulator circuit board and 2) to regulator U3. U3 is a +15 volt dc regulator. The output of U3 routed for application to the components on the power supply circuit board.

4-66. AC power from a second winding of transformer T1 is applied to bridge rectifier D10. D10

rectifies the ac potential into an unregulated +20V dc supply for application to the RF power module power amplifier circuit boards. AC power from a third winding of power transformer T1 is applied to bridge rectifier D11. D11 rectifies the ac potential into an unregulated +30V dc supply for application to the RF power module power amplifier circuit boards. AC power from a fourth winding of power transformer T1 is applied to bridge rectifier D12. D12 rectifies the ac potential into an unregulated +15V dc supply for application to: 1) the power supply circuit board and 2) regulator U4. U4 is a +12 volt dc regulator. The output of U4 routed for application to the components on the power supply circuit board.

4-67. An ac sample from a winding of T1 is also routed to a soft-start circuit. The soft-start

circuit is designed to generate control pulses synchronized with the ac line phase. A complete description of the soft-start circuit is presented in Rectifier/Soft-Start Circuit (refer to the following text).

4-68.

SWITCHING POWER SUPPLY CIRCUIT. AC power from the power factor corrector

circuitry is applied to fuses F1 and F2 on the power supply circuit board. The fuses protects the power supply circuitry from overload conditions. Metal-Oxide-Varistor MOV1 prevents damage to the switching power supply circuit from ac line voltage surge potentials.

4-69. Rectifier/Soft-Start Circuit. The ac line is full-wave rectified by an isolated SCR

controlled bridge rectifier circuit. The SCR bridge rectifier consists of diodes D15 through D17 and SCRs D13 and D14. The rectifier is controlled by a soft-start circuit. The soft-start circuit is designed to: 1) determine when the ac line waveform crosses the 0 volt axis and 2) generate short duration pulses in synchronization with the ac line 0 volt crossings. The pulses are amplified and applied to the gates of the rectifier circuit SCR components to slowly bias the components on during initial start operations. This operation eliminates the component stress at power-on by limiting the supply in-rush current. The rectifier will output an unregulated and unfiltered dc supply at approximately 300V to an inductor and capacitor filter network.

4-70. The output of the rectifier circuit is applied to afilter consisting of capacitors C24 through

C27. The output of the LC filter generates a 300V main operating supply for the RF power modules. The positive leg of the dc supply is the common for the dc voltages contained in the switching regulator circuitry and the RF power modules. The negative leg of the supply is regulated and controlled to generate the required operating potentials for the RF power modules.

4-71. Switching Regulator Circuit. The main operating supply is regulated by a buck-type

switching regulator circuit. The switching regulator circuit generates the negative leg of the B supply. The regulator circuit consists of: 1) a power supply mute circuit, 2) a switching regulator power control PWM circuit, 3) optical coupler U17 4) inverting buffer U19, and 5) switching regulator transistors Q21 and Q22.

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4-72. A dc operating supply for optical coupler U17 and buffer U19 is generated by bridge

rectifier D25. D25 full-wave rectifies an ac potential from ac transformer T1 into an unregulated +20V supply. The supply is applied to +18V regulator U16. U16 outputs a +18V supply which is further regulated to a 5V operating potential by a resistive divider and a zener diode. The 5V supply is applied to optical couplers U17 and buffer U19.

4-73. Control of the regulator circuit is provided by the switching regulator power control PWM

circuit, a current sampling circuit, and a voltage and current feedback correction circuit. Together, the circuits function in a closed-loop to control regulator operation. The switching regulator power control PWM circuit is designed to produce two out-of-phase square wave signals with varying duty cycles. The duty cycle is varied in response to the signal from the correction circuit. The output of the control circuit is applied to optical coupler U17. U17 provides isolation between two different ground circuits. The output of the coupler is applied to gate drive inverting buffer U19. The output of U19 is applied to the gates of IGBT switching regulator transistors Q21 and Q22. Q21 and Q22 are operated to on for a specific time duration to regulate the output voltage for varying load conditions.

4-74. The regulator circuit output voltage is directed by a 1 kHz power control PWM signal

from the controller. The signal is applied to the correction circuit on the power supply circuit board. In addition to the 1 kHz PWM signal, a voltage and current sample from the regulator output is routed to the voltage and current feedback correction circuit. The correction circuit responds by evaluating the output samples and the power control signal and generating a correction voltage. The voltage is applied to the switching regulator power control PWM circuit to adjust the output of the regulator.

4-75. The output of the transistor switching regulator circuit is applied to filter inductor L2.

Protection of the transistors from switching transients during turn on/off operation is provided by clamp diode D32. Clamp diode D32 protects the transistors by limiting positive peak voltages. The output of the regulator circuit is applied to circuitry on RF power module modulator circuit boards.

4-76.

MODULATOR CIRCUIT BOARD.

4-77. The B- leg from the power supply circuit board is routed to circuitry on the RF power

module modulator circuit board. The B- leg is applied to relay K1 on the modulator circuit board. K1 is controlled by a fault detector circuit. The relay is designed to immediately remove the supply from the forward converter circuit during a fault condition. The output of the relay is applied to the converter circuit.

4-78. Transistors Q1 and Q2 are the switching devices in the forward converter circuit. The

circuit is controlled by the audio PWM signal from the driver circuit board. The circuit operates by switching the applied B- leg at a 122 kHz to 135 kHz rate. The duty cycle of the PWM signal is 40% with no modulation. The output of the forward converter circuit is applied to an LC PWM low-pass filter network. Protection of the transistors from switching transients is provided by clamp diodes D2 and D3. D2 and D3 limit the positive peak transients appearing on the output.

4-79. A sample of the modulator circuit output is routed to a fault detector circuit. The circuit

will respond to a fault by: 1) routing a control signal to relay K1 to disconnect the amplifier circuit from the B- supply and 2) route a control signal to the power supply circuit board to momentarily mute the power supply. After a short delay, a control signal is routed to the power supply to enable the supply to provide power to RF module 2.

4-80. The B+ leg of the supply is also routed to the modulator circuit board. The B+ leg is

applied to fuse F1 and is the common for the dc voltages contained in the power supply circuit board switching regulator circuit and the RF power modules. F1 is provided to protect clamp diodes D2 and D3 from overcurrent conditions.

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4-81. POWER AMPLIFIER CIRCUIT BOARDS.

4-82. The power amplifier circuit board circuitry is configured in a Class E switching amplifier

design. A Class E design is recognized by: 1) the application of the B+ power supply through an RF choke to combining transformers and 2) the use of only two MOSFET power transistors in a push-pull configuration per amplifier. The circuitry on each amplifier circuit board is identical, therefore only amplifier circuit board 1 will be discussed.

4-83. The dc voltage output of the modulator circuit board is routed to the power amplifier 1

circuitry through fuse F1. F1 protects the amplifier circuitry from over-current conditions. The supply is applied to a switching amplifier circuit consisting of transistors Q1 and Q2. The B+ leg of the main dc supply from the power supply circuit board is applied to Q1 and Q2 through choke L4 to a primary center tap of combiner transformer T4. RF choke L4: 1) prevents RF signals from entering the dc supply and 2) functions as the last series inductor for the PWM low-pass filter on the modulator circuit board.

4-84. The amplifier circuit is driven by the RF drive signal from the exciter circuit board. The

RF drive signal consists of a square-wave signal at the carrier frequency. The signal is amplified prior to application to Q1 and Q2 by a driver circuit.

4-85. The amplifier circuit functions by switching the dc voltage from the modulator circuit

board at an RF rate to produce a monophonic or a C-QUAM AM stereo signal at the programmed carrier frequency. The signal appears at the primary of combiner transformer T4. The RF signal is transferred to the secondary of T4 and routed to power amplifier 2 circuit board combiner transformer T3. The RF output signal from T4 is combined with the RF output signal from transformer T3 to generate a C-QUAM signal at approximately 1375 watts of carrier.

4-86.

SEQUENCE OF OPERATION.

4-87. When transmitter switch S1 is closed, ac power is routed to contactor K2 and the ac line

monitor. If the ac power line is between 190 and 260 volts, power from K2 is applied to: 1) the power factor corrector circuitry, 2) the ECU power supply, 3) fan control relay K1, 4) low-voltage ac power transformer T1, and 5) the ac sample circuit board. If the ac line voltage is not between 190 and 260 volts, the ac line monitor will open K2 and deenergize the transmitter. When ac power is applied to T1, a soft start circuit will detect the ac waveform. When this occurs, the power factor corrector control circuit will energize the relays on the power factor corrector circuit board to switch capacitor C1 in the circuit. This enables the power factor corrector circuitry to change the power factor to approximately 0.9. In response to the application of ac power with no error conditions, the following controller and RF power module indicators will illuminate green:

CONTROLLER INDICATORS RF POWER MODULE INDICATORS

1. Exciter 1. PA 1 RF Drive

2. Power Modules 2. PA 2 RF Drive

3. Power Supply 3. PWM Drive

4. Antenna

5. Mono or Stereo (depending on exciter mode of operation)

6. Exciter Circuit Board: 1) +15V, 2) -15V

3) Lock, and 4) +5V

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7. Stereo Circuit Board: 1) Mono L+R/Stereo/ Mono L/Mono R (depending on exciter mode of operation), 2) Equalization 1 or Equalization 2 (depending on antenna configuration)

4-88. A start sequence is initiated when a power level switch/indicator is depressed. Logic from

the controller will enable optically-coupled-relay K1 to enable the flushing fans.

4-89. Logic from the controller will also enable the SCR controlled bridge rectifier circuit on the

power supply circuit board. The B+ dc potential from the rectifier is applied to the inductor and capacitor filter networks on the power supply panel. Generation of the Bleg is provided by the IGBT switching regulator circuit.

4-90. Power output of the regulator is controlled by the PWM signal from the controller. The

regulator will increase or decrease power as determined by the PWM signal. The output of the regulator is routed to the modulator circuit board. The modulator POWER indicator will illuminate if the B+ supply from the power supply circuit board is present. The modulated output from the modulator circuit board is routed to the power amplifier 1 and power amplifier 2 circuit board for amplification.

4-91.

RF CIRCUITRY.

4-92. EXCITER CIRCUIT BOARD. Audio for application to the AM-2.5E/AM-5E transmitter is

applied to the exciter circuit board (refer to Figure 4-4). The exciter circuit board is designed to: 1) process left/right channel or monaural audio to generate a Pulse-Width-Modulated (PWM) signal at 122 kHz to 135 kHz and 2) generate an RF signal using a frequency synthesizer, a phase modulator for IPM correction, and an RF driver network.

4-93. Left channel audio is applied to an RFI filter and a defeatable 10 Hz high-pass filter. The

10 Hz high-pass filter is provided to remove low frequency residual products from specific audio processing units. Balanced-to-unbalanced signal conversion is provided by an instrumentation amplifier. The output of the instrumentation amplifier is applied to a defeatable high frequency boost circuit. The high frequency boost circuit is provided to increase high frequency response to compensate for a Bessel filter in the PWM modulator. The output of the high frequency boost circuit is applied to an active PWM filter/equalizer and a mode switching circuit. The output of the PWM filter is routed for application to the stereo circuit board.

4-94. The mode switching circuit is designed to select the left or right channel for mono left or

mono right operation. A summing amplifier is provided as a mono support circuit to increase the gain of the circuit 6 dB during mono operations. The output of the summing amplifier is applied to a 24 uS delay and limiter circuit. The delay circuit is provided for stereo equalization. The negative limiter is provided to limit negative modulation from 90% to 100%.

4-95. The output of the 24 uS delay and negative limiter is applied to: 1) a PWM circuit and

2) an IPM comparator and corrector circuit. The PWM circuit is designed to output a

square wave signal in which the duty cycle changes in response to the applied audio level. The output of the PWM circuit is applied to a PWM driver circuit. The PWM driver circuit consists of parallel transistor drivers to lower the impedance and improve reliability.

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4-96. The transmitter carrier frequency is generated by digitally programmed frequency

synthesizer circuit. The frequency synthesizer is designed to output: 1) the carrier frequency to a mono/stereo select circuit, 2) a FcX4 (carrier frequency times four) signal for application to the stereo circuit board, and 3) a 25 Hz pilot signal for application to the stereo circuit board. A mono/stereo select circuit functions as an automatic mono/stereo select switch. If a stereo signal from the internal stereo circuit board or an external stereo generator is present, the exciter will be configured for stereo operation. If the stereo signal is not present, the circuit will configure the exciter for mono operation. The output of the mono/stereo select circuit is applied to the IPM (Incidental Phase Modulation) signal generator and modulator. The IPM signal generator is designed to produce a waveform similar to the signal produced by the RF amplifier circuitry. The IPM generator signal is out-of-phase with the signal generated by the RF power modules. The signal is applied to a modulator circuit which will generate a phase compensated RF signal at the carrier frequency. The phase compensation will effectively cancel the IPM generated in the RF circuitry.

4-97. The output of the IPM circuitry is applied to an RF driver network. The network consists

of a high/low side driver and output drive transistors.

4-98.

4-99. Left channel audio from the exciter circuit board is applied to the left channel

4-100. The output of each equalization circuit is routed to an equalization and mono/stereo select

4-101. The output of the equalization and mono/stereo select circuits is applied to a summing

STEREO CIRCUIT BOARD. Left/right channel audio and an RF signal at FcX4 (carrier

frequency times four) from the exciter circuit board is applied to the stereo circuit board. The stereo circuit board is designed to generate a TTL level RF signal. The circuit board contains identical left/right channel and equalization 1/2 circuitry. Therefore, only the left channel equalization 1 circuit will be discussed.

equalization 1 circuit. The equalization circuit consists of 1) a state variable low-pass filter, 2) an 8 uS group delay section, and 3) a 4 uS group delay section. The circuit is designed to equalize frequencies to produce maximum separation.

circuit. The equalization circuit selects equalization 1 or equalization 2 as determined by the selected antenna pattern. The mono/stereo circuit selects the required signals for stereo, mono left, mono right, or mono L+R operation.

amplifier network. The network functions as a matrix to generate the L+R and L-R stereo signals. The output of the summing amplifier network is applied to a digital switching modulator. The modulator accepts: 1) the L+R and L-R signals and 2) four RF out-of-phase signals at the carrier frequency. The modulator outputs two signals: 1) an AM modulated signal containing the L+R information and 2) a double-sidebandsuppressed-carrier signal referenced to a 90 degree carrier. The signals are summed and amplified at U37 to produce a quadrature signal. The output of U37 is applied to a fourth order linear phase bandpass filter. The output of the filter is applied to an amplitude limiter circuit. The limiting operation produces the phase modulation (L-R information) component of the C-QUAM signal. The output of the limiter circuit is routed to the exciter circuit board.

4-102.

RF POWER MODULE. The PWM and RF drive signals from the exciter circuit board are

routed to the RF power modules. The RF power modules consist of a modulator circuit board and two RF amplifier circuit boards.

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4-18

FIGURE 4-4. AM-2.5E/AM-5E RF CIRCUITRY SIMPLIFIED SCHEMATIC (SHEET 1 OF 2)

597-1113-18

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597-1113-18A

FIGURE 4-4. AM-2.5E/AM-5E RF CIRCUITRY

SIMPLIFIED SCHEMATIC (SHEET 2 OF 2)

(4-19/4-20)

Page 82

4-103. Modulator Circuit Board. The modulator circuit board consists of a MOSFET forward

converter circuit and a filter network. The forward converter circuit consists of MOSFET transistors Q1 and Q2. The filter network consists of inductors L1 through L3 and capacitors C13 through C16. A dc operating voltage for transistors Q1 and Q2 is provided by the power supply circuit board. The B- leg of the supply is routed through relay K1 to the transistors. K1 is provided to immediately terminate the supply during a modulator fault condition.

4-104. The PWM signal at a 15 volt level from the exciter circuit board is applied to the gates of

MOSFET transistors Q1 and Q2. Q1/Q2 function to switch the B- leg at a 122 kHz to 135 kHz rate. The output from Q1/Q2 is applied to the LC low-pass filter network to convert the square-wave PWM signal to a dc voltage. The output from the filter will produce a 50 volt dc signal with: 1) a nominal PWM duty cycle of 40% and 2) no audio modulation. The dc voltage will vary from 0 to 125 volts with -100% to +150% modulation. The output of the filter network is applied to the drains of MOSFET amplifier transistors on the power amplifier circuit boards.

4-105. Power Amplifier Circuit Boards. The RF circuitry on the power amplifier circuit boards

consists of a Class E MOSFET power amplifier circuit. Each power amplifier circuit board is designed to output approximately 350 watts. The power amplifier circuit boards are identical. Therefore, only power amplifier 1 will be discussed.

4-106. The MOSFET amplifier circuit is designed in a push-pull design Class E configuration.

Class E power amplifier characteristics consist of: 1) the transistor drain-to-source voltage must be nominally zero immediately prior to the turn-on of the transistor and

2) the time slope of the drain-to-source voltage waveform must be nominally zero prior to

the turn-on of the transistor. The Class E circuit results in: 1) lower device dissipation resulting in reduced transistor operating temperature which greatly increases component life, 2) an operating efficiency of 95% or greater, and 3) increased reliability when operated into VSWR conditions.

4-107. Additional characteristics of a Class E amplifier design is the application of dc power to

the amplifier transistors. The B+ leg of the B supply is applied to RF choke L1. The choke is connected to the primary center tap winding of combiner transformer T1. The transistors are connected to the primary winding of the transformers.

4-108. Two signals are applied to the power amplifier 1 circuit board: 1) an RF square-wave

signal from the driver circuit board and 2) a dc voltage from the modulator circuit board which varies at an audio rate. The RF square-wave signal at the carrier frequency is applied to the gates of MOSFETs Q1 and Q2. The varying dc voltage from the modulator circuit board is applied to the source of MOSFETs Q1 and Q2. Q1/Q2 operate in a push-pull configuration to develop approximately 350 watts of RF power at combiner transformer T1. The power at transformer T1 is combined with the 687.5 watts of RF power from power amplifier circuit board 2 to generate 1375 watts of RF power from the RF power module.

4-109.

RF COMBINER. The RF combiner components are located on the rear-panel of each

power block assembly. The combiner consists of a star combiner design. The star combiner contains an individual transformer, an RF choke, and an impedance matching circuit for each power amplifier circuit board. The impedance matching circuit consists of star inductors. The circuit presents the correct impedance when a module is removed from the chassis. This allows the transmitter to operate at an output power which is proportional to the modules removed from the power block chassis.

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4-110. HARMONIC BAND-PASS FILTER. The output signal harmonic and spur frequencies are

reduced to FCC, DOC, and CCIR levels by a band-pass filter. The filter consists of a fourth order LC network consisting of inductors L1 through L3 and capacitors C1 through C4. The components are located in the output network assembly and are frequency dependent. The output of the filter is routed to the directional coupler circuit board.

4-111.

4-112. Forward And Reflected Power Sample Circuit. A voltage sample from the RF output is

4-113. Modulation Monitor Calibration Circuit. A voltage sample for application to the

4-114. A voltage is applied to the modulation monitor receptacle when the power level 5

DIRECTIONAL COUPLER CIRCUIT BOARD. Transmitter forward and reflected power

are sampled by a directional coupler circuit board. The directional coupler circuit board is designed to: 1) process the forward and reflected power samples for application to the controller circuit board and 2) calibrate the RF modulation monitor sample.

obtained by transformer T203. A current sample of the RF output is obtained by transformers T201 and T202. The current sample is converted to a voltage by a resistor network and applied to transformer T203. A voltage proportional to the square root of the forward power is obtained by summing the voltage from the secondary of T203 with the voltage sample from T201. A voltage proportional to the square root of the reflected power is obtained by summing the voltage from the secondary of T203 and with the voltage sample from T202. The forward power sample voltage is half-wave rectified by diode D202. The reflected power sample voltage is half-wave rectified by diode D201. Diodes D205 through D208 and zener diodes D209 and D210 protect the rectifier diodes from overvoltage conditions. The rectified forward and reflected power samples are routed for application to the controller circuit board. Programmable header J206 is provided to increase the adjustment range of the directional coupler circuitry. The header is programmed at the factory for the adjustment range required by the transmitter.

modulation monitor calibration circuit is provided by the lightning detection circuit board. A sample from the RF output is obtained by a capacitor circuit and applied to a relay circuit on the directional coupler circuit board. The relay circuit is designed to select a voltage sample from a calibration potentiometer for application to the modulation monitor receptacle. The relays are controlled by power level 1 through 5 commands from the controller circuit board. Each relay circuit operates in an identical manner, therefore only the circuit for power level 5 will be explained.

command energizes relay K201. K201 applies a sample voltage to power level 5 modulation monitor calibration control R201. R201 is provided to obtain a 2 volt RMS sample to the modulation monitor receptacle. Frequency programming switch S201 is provided to compensate the RF sample for frequencies within the AM band for power levels 1 through 3. Power level programming switch P203 is provided to program the power level 3 circuit for low power range or high power range operation. The calibrated sample from potentiometer R201 is applied to the modulation monitor receptacle.

4-115.

4-116. LIGHTNING PROTECTION CIRCUIT BOARD. The transmitter is protected from

T-MATCHING NETWORK. Output matching to antenna loads for up to a VSWR

condition of 1.4:1 at any phase angle relative to the 50 Ohm load is provided by a T-matching network. The T-matching network consists of tune control L4, load control L6, inductor L5 and capacitor C5/C5A. Inductor L5 and capacitor C5/C5A are frequency dependent components. The tune and load controls are designed to be adjusted to present the optimum impedance for the power amplifier modules.

lightning potentials present at the output network by the lightning protection circuit board. The circuit board consists of series connected transzorbs. The AM-2.5E transmitter is equipped with transzorbs D1 through D6. The AM-5E transmitter is equipped with transzorbs D1 through D7. The transzorbs are designed to conduct the lightning potentials to ground prior to the operation of the lightning detection circuit spark-gap.

4-22

Page 84

4-117. LIGHTNING DETECTION CIRCUIT BOARD. Lightning potentials present at the

transmitter output are detected by the lightning detection circuit board. The circuit board is equipped with an RF sampling circuit and an optically operated transistor circuit.

4-118. The RF sampling circuit consists of a parallel capacitor circuit. The circuit is designed to

provide a constant RF voltage sample for application to the directional coupler circuit board. The optically operated transistor circuit is designed to detect lightning potentials present at the transmitter output. The circuit operates in association with the lightning detector spark-gap. When lightning is present at the transmitter RF output, the spark-gap will: 1) be biased on to conduct the potential to ground and 2) emit a light pulse to optically operated transistor Q401. Q401 will be biased on to output a lightning detect signal to the controller circuit board.

4-119.

RF OUTPUT POWER CONTROL CIRCUITRY. The transmitter output power is controlled

by circuitry on the controller and power supply circuit boards. The transmitter power level is controlled by a Pulse-Width-Modulated (PWM) signal generated by the controller circuit board. The power control PWM signal is routed for application to the power supply circuit board(s). The power supply circuit board(s) respond by routing the required dc voltage to the modulator circuit boards and the RF amplifier circuit boards. The following text presents a description of the RF power control circuitry.

4-120. RF Output Power Control - Controller Circuit Board. A transmitter RF output power level

is selected by the power control 1 through power control 5 switch/indicators. The power control switch/indicators route a LOW control signal to a priority encoder circuit. The priority encoder circuit determines which control pulse is routed to the power control circuitry. The circuit allows transmitter off commands to be assigned a high priority. With no transmitter off commands present, the power control signal is applied to multiplexer U39. U39 selects a reference voltage from the power control potentiometers on the controller circuit board. The potentiometers are designed to establish a preset transmitter power level such as 1 kW. The voltage is used as the reference for digital-to-analog converter U42. With no fault conditions present, the voltage is applied without change to power trim digital-to-analog converter U43. With no power trim commands present, the reference voltage is applied to a driver circuit which converts the dc control voltage to a power control PWM signal. The power control PWM duty cycle responds to the changes in the voltage reference level. When the voltage reference increases, the power control PWM signal duty-cycle increases. When the voltage reference decreases, the power control PWM signal duty-cycle decreases. The power control PWM signal is routed for application to the power supply circuit board(s).

4-121. The transmitter output power level is trimmed to a precise level by the power up and

down switches. The switches output a LOW control signal to a control logic circuit. The control logic circuit generates the required control signals to drive an up/down counter circuit. The circuit is designed to: 1) count up if power is required to be increased or

2) count down if power is required to be decreased. The up/down counter circuit output is

converted to a dc potential by digital-to-analog converter U43. The output of U43 is summed with the dc potential from power control switch digital-to-analog converter U42 to generate a dc power control signal. The power control signal is applied to the driver circuit which converts the signal to a power control PWM signal.

4-122. Automatic Power Control Circuitry. The transmitter power control circuitry is equipped

with several monitor circuits designed to determine if power control correction is required during adverse operating conditions. Circuitry on the controller circuit board monitors the transmitter components and the RF output for: 1) lightning, 2) high forward power,

3) high reflected power, and 4) over-temperature. If a lightning, high forward power,

high reflected power, or over-temperature, condition occurs, a signal is routed to the fault detection circuit.

4-23

Page 85

4-123. The fault detection circuit: 1) processes lightning and over-temperature signals and

2) analyzes forward and reflected power signals. As determined by the the fault

condition, the fault detection circuit will generate a fast or slow control signal to the up/down counter circuit. The counter circuit will respond by decreasing the power control voltage at digital-to-analog converter U42. U42 will respond by decreasing the output power to an acceptable level. Once the condition which caused the fault to occur is removed, the fault detection circuitry will automatically output a control signal to increase power to a normal level.

4-124. Forward/Reflected Power Circuitry. Samples of the transmitter forward and reflected

power are processed by forward and reflected power circuits on the controller circuit board. Forward power samples from the directional coupler circuit board are applied to the forward power circuit. The forward power circuit converts the sample into a dc signal for application to the fault detection circuitry and to the meter switch circuit board. Reflected power samples from the directional coupler circuit board are applied to the reflected power circuit. The reflected power circuit converts the sample into a dc signal for application to the fault detection circuit and the meter switch circuit board.

4-125. Meter Switch Circuit Board. Forward and Reflected power samples from the controller

circuit board are applied to the meter switch circuit board. The circuit board allows the selection of forward power, reflected power, and ac input samples for display on forward power meter M1 and reflected power meter M2.

4-126. RF Output Power Control - Power Supply Circuit Board/RF Power Modules. The power

control PWM signal from the controller circuit board is applied to a correction circuit on the power supply circuit board. The PWM signal is converted to a dc signal and combined with a dc feedback signal to generate a power control signal for application to the switch regulator power control PWM circuit. The circuit converts the dc signal into two PWM 180 degree out-of-phase square-wave drive signals. The square-wave drive signals are applied to a driver circuit. The driver circuit outputs the out-of-phase square-wave signals to an IGBT transistor regulator circuit. The regulator circuit transistors are operated to on for a specific time duration to generate a specific B- supply voltage. The B- supply voltage is filtered by capacitor C55 and applied to the forward power converter on the modulator circuit boards.

4-127. The main operating supply B+ leg is created by a SCR controlled bridge rectifier circuit.

AC power from an ac input filter is applied to the SCR controlled bridge rectifier. The rectifier is controlled by a soft-start circuit. The full-wave rectified dc potential is filtered by capacitors C24 through C27. The output of the filter generates the positive leg of a B supply. The B+ line of the power supply is applied to the forward power converter circuit on modulator circuit boards and the RF amplifier transistors on RF amplifier circuit boards.

4-128. To provide an example of output power control operation, a 10 kW output level is required

from the transmitter. The controller power control PWM duty-cycle will be approximately 85%. The power supply will respond by generating a 120 volt B- supply for application to the forward power converter on the modulator circuit boards. The modulator circuit boards will output a dc voltage which varies at an audio rate to the amplifier circuit boards. The amplifier circuit boards will respond by using the modulator circuit board dc voltage and the B+ leg of the main supply to amplify the RF drive signal from the exciter circuit board.

4-24

Page 86

SECTION V

MAINTENANCE

5-1. INTRODUCTION.

5-2. This section provides maintenance information, electrical adjustment procedures, and

troubleshooting information for the Broadcast Electronics AM-2.5E and AM-5E transmitters.

5-3.

SAFETY CONSIDERATIONS.

WARNING

THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT GROUNDS WITH HIGH AC AND DC POTENTIALS

WARNING

WITH RESPECT TO THE CABINET WHICH IS AT EARTH POTENTIAL. DO NOT ENERGIZE THE TRANSMITTER WITH TEST EQUIPMENT CON NECTED TO THE TRANSMITTER OUTPUT NETWORK, RF POWER MODULE, RF COMBINER, OR POWER SUPPLY COMPONENTS.

5-4. The AM-2.5E/AM-5E transmitters contain high voltages and currents. If safety

precautions are not practiced, contact with the high voltages and currents could cause serious injury or death. The transmitter is equipped with many built-in safety features, however good judgement, care, and common sense must be practiced to prevent accidents.

5-5. In addition to high voltages and currents, the transmitter contains multiple circuit

grounds with high ac and dc potentials with respect to the cabinet which is at earth potential. The potentials could cause serious injury or death if maintenance personnel simultaneously touch a circuit ground and the cabinet. As a result, operation of the transmitter with test equipment connected to transmitter output network, RF power module, RF combiner, or power supply components is extremely dangerous and must not be attempted. Therefore, never energize the transmitter with test equipment connected to the transmitter output network, RF power module, RF combiner, or power supply components. Test equipment may be connected to the ECU circuit boards from the front of the transmitter using the supplied extender circuit board with power energized. The maintenance procedures presented in this section should be performed only by trained and experienced maintenance personnel.

5-6.

5-7. First level maintenance consists of procedures applied to the equipment to prevent future

5-8.

FIRST LEVEL MAINTENANCE.

failures. The procedures are performed on a regular basis and the results recorded in a maintenance log. Preventive maintenance of the transmitter consists of good housekeeping and checking performance levels using the meters and various indicators built into the equipment.

ROUTINE MAINTENANCE.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-1

Page 87

WARNING

NEVER OPEN THE EQUIPMENT UNLESS ALL TRANS MITTER PRIMARY POWER IS DISCONNECTED. EN

WARNING

SURE ALL TRANSMITTER PRIMARY POWER IS DIS CONNECTED BEFORE ATTEMPTING MAINTENANCE ON ANY AREA WITHIN THE TRANSMITTER.

5-9. INSPECTION AND CLEANING. On a regular basis, clean the equipment of accumulated

dust using a brush and vacuum cleaner. Inspect the modulator circuit boards, RF amplifier circuit boards, and the power supply circuit boards for damage caused by components overheating. Overheated components are identified by circuit board discoloration near the component leads. Inspect the circuit boards for loose hardware as required.

5-10.

5-11.

5-12.

CONTROLLER BATTERY. Periodically, the controller battery in the ECU assembly should

be checked by depressing the battery test switch on the controller circuit board. The battery test indicator will illuminate to indicate the battery is operational. If the battery test indicator fails to illuminate, the battery must be replaced. A good-quality Alkaline battery is recommended for replacement. Typically, it is recommended the controller battery be replaced annually.

AIR FILTERS. The AM-2.5E/AM-5E transmitters are equipped with a single screen-type

air filter. The screen filter is designed to be removed and cleaned using a brush and vacuum. A dirty filter results in restricted air flow and increased operating temperatures for the transmitter solid-state components. Check the filter approximately once a week. The filter is designed to be removed during transmitter operation. To remove the filter, proceed as follows:

1. Refer to Figure 5-1 and remove the six filter housing screws.

2. Using the handles, lift the filter housing off of the rear door.

3. Remove the filter.

FLUSHING FANS. Inspect the transmitter flushing fans for dust accumulation and

periodically clean the fans using a brush and vacuum cleaner. Do not use compressed air and an air gun. The fans are cooled by air passing around each motor. If dust is allowed to accumulate on the motors, the ambient air temperature will increase due to restricted air flow. When the ambient air temperature increases, the fan motor bearing lubricant will gradually vaporize and bearing failure will occur.

5-13. It is recommended the flushing fan mounting hardware be periodically checked. The

flushing fans are equipped with sealed bearings which do not permit lubrication. If a bearing fails, the motor must be replaced.

5-14.

5-15. SECOND LEVEL MAINTENANCE.

5-16. Second level maintenance consists of procedures required to adjust the transmitter

SPARK GAP. The output network is equipped with a spark gap. The spark gap is

provided to safely conduct lightning potentials appearing at the transmitter output to ground. Inspect the spark gap annually to ensure the gap is operational.

circuitry or restore the transmitter to operation after a fault has occurred. The procedures consist of electrical adjustments, troubleshooting, and component replacement procedures.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-2

Page 88

FIGURE 5-1. REMOVING THE AIR FILTER

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-15

5-3

Page 89

WARNING

NEVER OPEN THE EQUIPMENT UNLESS ALL TRANS MITTER PRIMARY POWER IS DISCONNECTED. EN

WARNING

SURE ALL TRANSMITTER PRIMARY POWER IS DIS CONNECTED BEFORE ATTEMPTING MAINTENANCE ON ANY AREA WITHIN THE TRANSMITTER.

5-17. The maintenance philosophy for the AM-2.5E/AM-5E transmitters consists of isolating a

problem to a specific area. Once the specific area is located, subsequent troubleshooting using the information in the following text and the modular sections in PART II of this manual will assist in problem isolation to a replaceable assembly or component. If required, the assembly may be: 1) returned to the factory for repair or exchange or

2) repaired locally.

5-18.

ELECTRICAL ADJUSTMENTS.

WARNING

NEVER OPEN THE EQUIPMENT UNLESS ALL TRANS MITTER PRIMARY POWER IS DISCONNECTED. EN

WARNING

SURE ALL TRANSMITTER PRIMARY POWER IS DIS CONNECTED BEFORE ATTEMPTING MAINTENANCE ON ANY AREA WITHIN THE TRANSMITTER.

5-19. Adjustment procedures for controls associated with the transmitter circuitry is presented

in the ECU, output network, RF power module, and power supply module sections of this manual. Determine the transmitter modular component requiring adjustment and refer to the appropriate section of this manual for the adjustment procedures.

5-20.

5-21. The AM-2.5E/AM-5E transmitters are configured for a specific frequency when shipped

5-22.

TRANSMITTER FREQUENCY RE-PROGRAMMING.

from the factory. The transmitters are equipped with several frequency dependent parts and circuits. Due to the frequency dependent parts, frequency dependent circuits, and specialized procedures, the transmitters can not be reprogrammed for a different frequency in the field. If a transmitter is required to be programmed for a different frequency, contact the Broadcast Electronics Customer Service department.

TROUBLESHOOTING.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-4

Page 90

WARNING

THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT GROUNDS WITH HIGH AC AND DC POTENTIALS

WARNING

5-23. The AM-2.5E/AM-5E transmitters are equipped with extensive indicator and meter

circuitry to allow the operator to isolate problems to a specific area within the transmitter. Due to the hazardous voltages and currents contained in the equipment, operation of the transmitter with test equipment connected to transmitter output network, RF power module, RF combiner, or power supply components is extremely dangerous and must not be attempted. Test equipment may be connected to the ECU circuit boards from the front of the transmitter using the supplied extender circuit board with power energized. Therefore, the transmitter indicators and meters must be used to isolate a problem to a specific area.

5-24.

TRANSMITTER INDICATORS. The following text presents a description of the transmitter

indicators and typical meter indications. Refer to the following text as required to determine the function of a specific indicator.

ASSEMBLY INDICATOR FUNCTION

ECU ASSEMBLY

TRANSMITTER MONITOR

EXCITER GREEN DISPLAY - Indicates normal exciter

POWER MODULES GREEN DISPLAY - Indicates all RF power modules

POWER SUPPLY GREEN DISPLAY - Indicates normal power supply

TABLE 5-1. AM-2.5E/AM-5E INDICATORS

(Sheet 1 of 4)

operation. RED DISPLAY - Indicates no exciter RF drive or PWM output.

are operating normally. YELLOW DISPLAY - Indicates one or more RF power modules are removed from the transmitter for maintenance. RED DISPLAY - Indicates a modulator or power amplifier circuit board fault in one or more RF power modules.

operation. RED DISPLAY - Indicates an open loop or overvoltage fault in one or more power supply modules. YELLOW Display - Indicates one or more power supplies are removed from the transmitter.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-5

Page 91

TABLE 5-1. AM-2.5E/AM-5E INDICATORS

(Sheet 2 of 4)

ASSEMBLY INDICATOR FUNCTION

ANTENNA VSWR GREEN DISPLAY - Indicates a normal antenna load.

YELLOW DISPLAY - Indicates a VSWR condition of

1.2:1. RED Display - Indicates a high reflected/forward power condition. In the AM-2.5E, indicates a 100 watt reflected power condition or a condition which results in a high forward power indication of greater than 20%. In the AM-5E, indicates a 200 watt reflected power condition or a condition which results in a high forward power indication of greater than 20%. FLASHING RED Display - Indicates a reflected power emergency condition. In the AM-2.5E, indicates a 500 watt reflected power condition. In the AM-5E, indicates a 1000 watt reflected power condition.

REMOTE Illuminates to indicate transmitter remote control

operations are enabled. Extinguishes to indicate transmitter remote control operations are disabled:

1) using the remote/local switch on the controller circuit board or 2) due to a fault in the remote control unit.

CONFLICT Illuminates to indicate an incorrect power level is

selected for operation into the antenna connected to the

transmitter.

LIGHTNING In the AM-2.5E, Illuminates to indicate a 1500 volt

or greater potential is present at the transmitter output. In the AM-5E, illuminates to indicate a 2100 volt or greater potential is present at the transmitter output.

INTERLOCK Illuminates to indicate all internal and external

interlocks are closed.

FOLDBACK Illuminates to indicate when the transmitter is in a

4) detection of a lightning potential.

OVERTEMP Illuminates to indicate when the transmitter operating

temperature exceeds 70 °C (158 °F).

RESET Illuminates to indicate one or more of the following

transmitter faults have occurred: 1) over-temperature,

2) exciter fault, 3) power supply fault, 4) RF power module fault, 5) high reflected power, 6) reflected power emergency, or 7) lightning. Once the fault condition is removed, the fault circuitry must be reset.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-6

Page 92

TABLE 5-1. AM2.5E/AM-5E INDICATORS

(Sheet 3 of 4)

ASSEMBLY INDICATOR FUNCTION

CONTROLLER CIRCUIT BOARD

PWM Mute Illuminates to indicate the power control PWM signal is

muted in response to a fault such as lightning, an exciter

fault, a reflected power emergency, an open remote

control failsafe, an external transmitter mute, lightning,

or high reflected or forward power.

Remote Failsafe Illuminates to indicate the remote control unit is

enabled.

Battery OK When the battery test switch is depressed, the indicator

will: 1) illuminate to indicate the battery is operational or 2) not illuminate to indicate the battery is to be replaced.

STEREO CIRCUIT BOARD

Stereo Equalization 1 Illuminates to indicate stereo equalization circuit 1 is

active.

Stereo Equalization 2 Illuminates to indicate stereo equalization circuit 2 is

active.

EXCITER CIRCUIT BOARD

Exciter Lock Illuminates to indicate the exciter is locked to the

programmed carrier frequency.

Exciter +5V Illuminates to indicate the ECU +5V supply is

operational.

Exciter +15V Illuminates to indicate the ECU +15V supply is

operational.

Exciter -15V Illuminates to indicate the ECU -15V supply is

operational.

RF POWER MODULE

PA 1 RF DRIVE Illuminates to indicate RF drive from the exciter circuit

board is present at power amplifier 1.

PA 1 FAULT Illuminates to indicate a fault has occurred in power

amplifier 1.

PA 2 RF DRIVE Illuminates to indicate RF drive from the exciter circuit

board is present at power amplifier 2.

PA 2 FAULT Illuminates to indicate a fault has occurred in power

amplifier 2.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-7

Page 93

TABLE 5-1. AM-2.5E/AM-5E INDICATORS

(Sheet 4 of 4)

ASSEMBLY INDICATOR FUNCTION

MOD PWM DRIVE Illuminates to indicate the PWM drive signal from the

exciter is present at the modulator circuit board.

MOD POWER Illuminates to indicate dc power from the power supply

circuit board is present at the modulator circuit board.

MOD FAULT Illuminates to indicate a modulator, fuse, or power

supply fault has occurred in the modulator circuit board.

MOD FUSE Illuminates to indicate the modulator circuit board fuse

has blown.

POWER SUPPLY 1-2 Illuminates to indicate an open loop, over-current,

or over-voltage fault in the 1-2 power supply. The supply provides power for modules 1-2.

POWER SUPPLY 3-4 Illuminates to indicate an open loop, over-current,

(AM-5E Only) or over-voltage fault in the 3-4 power supply. The

supply provides power for modules 3-4.

Exciter -15V Illuminates to indicate the ECU -15V supply is

operational.

CAUTION

WHEN AC POWER IS APPLIED TO THE TRANSMIT TER AND THE RF DRIVE AND PWM DRIVE INDICA

CAUTION

TORS ON RF POWER MODULES IN A POWER BLOCK ARE EXTINGUISHED, THE RF POWER MODULES MUST BE REMOVED FROM THE TRANSMITTER CHASSIS TO PREVENT DAMAGE TO THE MODULES.

5-25. RF POWER MODULE REMOVAL. When ac power is applied to the transmitter, check the

RF DRIVE and PWM DRIVE indicators on the RF power modules. If the RF DRIVE and PWM DRIVE indicators on RF power modules in a power block are extinguished, the RF power modules must be removed from the transmitter to prevent damage to the modules.

5-26.

5-27.

TRANSMITTER TROUBLESHOOTING PROCEDURES. Table 5-2 presents troubleshooting

information for the AM-2.5E/AM-5E transmitters. Refer to Table 5-2 to isolate the problem to a specific assembly. Once the trouble is isolated, refer to the applicable modular section of this manual for the theory of operation and schematic diagrams to assist in problem resolution.

TRANSMITTER COMPONENT LOCATIONS. Figures 5-2 through 5-4 present

transmitter component locations. Refer to Figures 5-2 to 5-4 as required during the troubleshooting procedures to locate components within the transmitter.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-8

Page 94

TABLE 5-2. AM-2.5E/AM-5E TROUBLESHOOTING

(Sheet 1 of 5)

SYMPTOM CIRCUITRY TO CHECK

NO OUTPUT POWER 1. Check the ac line voltage using the reflected power/ NO NORMAL/FAULT ac voltage meter. If no line voltage is present, check INDICATIONS fuses F1 and F2.

2. Check the ±15 volt and +5 volt indicators on the

exciter circuit board. If no indicators are illuminated, check the ECU power supply.

NO OUTPUT POWER 1. Transmitter operated to off due to 7 on/off cycles NORMAL INDICATIONS within 15 seconds. Operate the transmitter to on NO CONTROL OPERATIONS as follows: 1) do not depress any controller

switch/indicators for approximately 30 seconds and

2) depress the desired power level switch/indicator.

2. Refer to the POWER SUPPLY section and troubleshoot the power supply circuit board for no 120 Hz signal output.

RED EXCITER INDICATION 1. Check the lock indicator on the exciter circuit

board. If the lock indicator is not illuminated, refer to the ECU section and troubleshoot the exciter circuit board for lock indicator extinguished.

2. Remove the stereo circuit board and perform the following: 1) depress the RESET switch and

2) initiate transmitter operation. If the transmitter will not operate, refer to the ECU section and troubleshoot the exciter circuit board. If the transmitter operates, refer to the ECU section and troubleshoot the stereo circuit board.

YELLOW POWER MODULE 1. Indicates one or more RF power modules are INDICATION removed from the transmitter.

RED POWER MODULE 1. Refer to the RF POWER MODULE section and INDICATION RED FAULT troubleshoot the RF power module. INDICATION ON A MODULE 2. Visually inspect the RF power module combiner

panel for discolored components.

YELLOW POWER SUPPLY 1. Indicates one or more power supply modules are INDICATION removed from the transmitter.

RED POWER SUPPLY 1. Check for an over-temperature condition by INDICATION inspecting the fans and filter.

2. If the fans and filter are normal, use the power supply fault display circuit boards in each cabinet to determine the defective power supply module. When the defective power supply is located, refer to the POWER SUPPLY MODULE section and troubleshoot the power supply module.

5-9

WARNING: DISCONNECT POWER PRIOR TO SERVICING

Page 95

TABLE 5-2. AM-2.5E/AM-5E TROUBLESHOOTING

(Sheet 2 of 5)

SYMPTOM CIRCUITRY TO CHECK

YELLOW ANTENNA INDICATION 1. Check the antenna and phasor equipment.

2. Visually inspect the T-matching network for discolored components.

3. Refer to the OUTPUT NETWORK section and troubleshoot the directional coupler circuit board.

RED ANTENNA INDICATION 1. Check the antenna and phasor equipment.

2. Visually inspect the T-matching network for discolored components.

3. Refer to the OUTPUT NETWORK section of this manual and troubleshoot the directional coupler circuit board.

FLASHING RED ANTENNA 1. Check the antenna and phasor equipment. INDICATION 2. Visually inspect the spark gap in the output network

assembly for a short circuit condition.

3. Check the antenna shorting switch on the output network assembly.

4. Visually inspect the T-matching network capacitors in the output network assembly for a short circuit condition.

5. Check the lightning protection circuit board in the output network assembly for a short circuit condition.

INTERLOCK INDICATOR 1. Operate remote/local switch to local. EXTINGUISHED WHEN IN THE A. If the interlock indicator illuminates, ensure REMOTE CONTROL MODE a +5 volt signal is applied to remote failsafe

input J1-23 on the ECU rear-panel when the remote control unit is enabled.

1. If the +5 volt signal is not present, troubleshoot the remote control unit.

2. If the +5 volt signal is present, check Q48 and U56 on the controller circuit board.

B. If the interlock indicator is extinguished,

check the cabinet and the external interlocks.

CONFLICT INDICATION 1. Ensure a +5 volt status signal from the selected

antenna is applied to the antenna A, B, or C input on the ECU rear-panel.

2. Ensure the correct transmitter power level is selected for operation into the antenna.

3. Check the antenna interlock circuit programming on the controller circuit board.

4. Refer to the ECU section and troubleshoot the controller circuit board for a conflict indication.

WARNING: DISCONNECT POWER PRIOR TO SERVICING

5-10

Page 96

TABLE 5-2. AM-2.5E/AM-5E TROUBLESHOOTING

(Sheet 3 of 5)

SYMPTOM CIRCUITRY TO CHECK

NO OUTPUT POWER 1. Transmitter operated to off due to 7 on/off cycles LIGHTNING INDICATOR within 15 seconds. Operate the transmitter to ILLUMINATED on as follows: 1) do not depress any controller

switch/indicators for approximately 30 seconds and 2) depress the desired power level switch/indicator.

2. Ensure J1 on output network is connected.

3. Check Q401 on the lightning detection circuit board.

NORMAL OUTPUT POWER 1. Indicates the presence of lightning at the output of LIGHTNING INDICATOR transmitter. Depress the RESET switch to reset the ILLUMINATED indicator.

INTERLOCK INDICATOR 1. Ensure a +5 volt signal is applied to external EXTINGUISHED interlock input J1-23 on the ECU rear panel.

OVERTEMP INDICATOR 1. Ensure the transmitter air filter is clean. ILLUMINATED 2. Check the transmitter fans in each cabinet. If the

fans are not operating, check optical-coupled-relay (OCR) K1.

3. Ensure the transmitter exhaust area is clear of obstructions.

MISSING NORMAL/FAULT 1. Check the fuses for the power supply: 1) power INDICATIONS FOR A POWER supply 1-2 = F6 and F7, 2) power supply 3-4 = BLOCK F8 and F9 (AM-5E only).

2. Check power transformer T1 on the power supply panel.

NO L+R MODULATION ACTIVITY 1. Ensure audio is present at J3-1/J3-2/J3-4/J3-5 DURING MONO OPERATION on the ECU rear panel.

2. Check for audio at J101-29 through J101-31 and J101-36/J101-37 on the ECU motherboard. If no audio is present, check the filter components on the ECU motherboard.

3. Refer to the ECU section and troubleshoot the exciter circuit board.

NO L+R MODULATION ACTIVITY 1. Ensure audio is present at J3-1/J3-2/J3-4/J3-5 on DURING STEREO OPERATION the ECU rear panel.

2. Check for audio at J101-29 through J101-31 and J101-36/J101-37 on the ECU motherboard. If no audio is present, check the filter components on the ECU motherboard.

3. Refer to the ECU section and troubleshoot the exciter circuit board.

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TABLE 5-2. AM-2.5E/AM-5E TROUBLESHOOTING

(Sheet 4 of 5)

SYMPTOM CIRCUITRY TO CHECK

RF DRIVE INDICATORS 1. Check the RF drive output on the ECU motherboard EXTINGUISHED FOR A as follows: 1) output 1 -P101-7 and 2) output 2 POWER BLOCK P101-47 (AM-5E only).

1. If no RF drive is present, refer to the ECU section and troubleshoot the exciter circuit board.

2. If RF drive is present at the exciter circuit board, check bridge rectifiers D10 and D11 on the power supply module for the power block.

2. Refer to the RF POWER MODULE section and troubleshoot each RF power module.

LOW DEMODULATOR LEFT 1. Refer to the ECU section and troubleshoot the CHANNEL MODULATION LEVEL exciter circuit board. WITH LOW EXCITER MONITOR LEFT CHANNEL MODULATION LEVEL

LOW DEMODULATOR RIGHT 1. Refer to the ECU section and troubleshoot the CHANNEL MODULATION LEVEL exciter circuit board. WITH LOW EXCITER MONITOR RIGHT CHANNEL MODULATION LEVEL

LOW DEMODULATOR LEFT 1. Refer to the ECU section and troubleshoot the CHANNEL MODULATION LEVEL stereo circuit board. WITH NORMAL EXCITER MONITOR LEFT CHANNEL MODULATION LEVEL

LOW DEMODULATOR RIGHT 1. Refer to the ECU section and troubleshoot the CHANNEL MODULATION LEVEL stereo circuit board. WITH NORMAL EXCITER MONITOR RIGHT CHANNEL MODULATION LEVEL

PWM DRIVE INDICATOR 1. Refer to the ECU section and troubleshoot the EXTINGUISHED ON A POWER exciter circuit board. BLOCK

PWM DRIVE AND RF DRIVE 1. Refer to the ECU section and troubleshoot the exciter INDICATORS EXTINGUISHED circuit board. ON ALL POWER BLOCKS

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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TABLE 5-2. AM-2.5E/AM-5E TROUBLESHOOTING

(Sheet 5 of 5)

SYMPTOM CIRCUITRY TO CHECK

MOD PWR INDICATORS 1. Check for a power control PWM signal at the EXTINGUISHED ON A POWER drain of Q22 on the controller circuit board. BLOCK A. If the PWM signal is not present, refer to the

ECU section and troubleshoot the controller circuit board for no power control PWM signal.

B. If the PWM output is present, check for a LOW at

Q13 on the controller circuit board.

1. If the LOW at Q13 is not present, refer to the ECU section and troubleshoot the controller circuit board for no transmitter on signal.

2. If the LOW at Q13 is present, refer to the POWER SUPPLY section and troubleshoot the power supply for no MOD POWER indicator on a power block.

REFLECTED POWER METER 1. Narrow-band antenna. Contact the Broadcast FLUCTUATES WITH MODULATION Electronics Customer Service Department.

FORWARD POWER METER 1. Enable the high-pass filter on the exciter circuit FLUCTUATES WITH MODULATION board.

5-28. COMPONENT REPLACEMENT PROCEDURE. Component replacement on printed

circuit boards requires extreme care to avoid damage to the circuit board traces. The following text describes the procedure to replace components on the circuit boards.

5-29. On all circuit boards, the adhesive securing the copper trace to the board melts at almost

the same temperature at which solder melts. A circuit board trace can be destroyed by excessive heat or lateral movement during soldering. Use of a small iron with steady pressure is required for circuit board repairs.

5-30. To remove a component from a circuit board, cut the leads from the body of the defective

component while the device is still soldered to the board.

5-31. Grip each component lead, one at a time, with long-nose pliers. Rotate the circuit board

and touch a soldering iron to the lead at the solder connection. When the solder begins to melt, push the lead through the back side of the board. Each lead may now be heated independently and pulled out of each hole. The holes may be cleared of solder by carefully re-heating each hole with a low wattage iron and removing the residual solder with a soldering vacuum tool.

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Page 99

WARNING

MOST SOLVENTS WHICH WILL REMOVE ROSIN FLUX ARE VOLATILE AND TOXIC BY THEIR NATURE AND

WARNING

5-32. Install the new component and apply solder from the bottom side of the circuit board.

After soldering, remove flux with a cotton swab moistened with a suitable solvent. Rubbing alcohol is highly diluted and is not effective.

5-33. The board should be checked to ensure the flux has been removed and not just smeared.

Rosin flux is not normally corrosive, but rosin will absorb enough moisture in time to become conductive and cause problems.

SHOULD BE USED ONLY IN SMALL AMOUNTS IN A WELL VENTILATED AREA, AWAY FROM FLAME SUCH AS FROM A SOLDERING IRON OR SMOKING MATERI ALS. OBSERVE THE MANUFACTURER'S CAU TIONARY INSTRUCTIONS.

5-34.

INTEGRATED CIRCUITS. Special care should be exercised with integrated circuits. Each

integrated circuit must be installed by matching the integrated circuit notch with the notch on the socket. Do not attempt to remove an integrated circuit from a socket with your fingers. Use an integrated circuit puller to lightly pry the component from the socket.

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5-15

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-18

FIGURE 5-2. AM-2.5E COMPONENT LOCATOR (SHEET 1 OF 3)