BEI Electronics 7EPTX-AM2-5E AM-2.5E, 2.5 KW AM Stereo Transmitter User Manual WARNINGS

BEI Electronics, LLC AM-2.5E, 2.5 KW AM Stereo Transmitter WARNINGS

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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 POSSI-

BLY 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 includ-

ing blindness. Cardiac pacemakers may be affected.

The effect of prolonged exposure to “low level” RF radiation continues to be a subject of investigation and controver-

sy. It is generally agreed that prolonged exposure of personnel to RF radiation should be limited to an absolute mini-

mum. It is also generally agreed that exposure should be reduced in working areas where personnel heat load is

above normal. A 10 mW/cm2 per one tenth hour average level has been adopted by several U.S. Government agen-

cies including the Occupational Safety and Health Administration (OSHA) as the standard protection guide for em-

ployee work environments. An even stricter standard is recommended by the American National Standards Institute

which recommends a 1.0 mW/cm2 per one tenth hour average level exposure between 30 Hz and 300 MHz as the

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 regu-

lar 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 oper-

ated to off. To prevent serious burns, take care to prevent and avoid any bodily contact with these surfaces both dur-

ing and for a reasonable cooling down period after operation.

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 ElecĆ

tronics. However, the transmitter must be properly installed at a site with adequate

lightning protection and transmission line systems. TO ENSURE THE TRANSMITĆ

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 LIGHTĆ

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, conĆ

tact the Broadcast Electronics Customer Service Department.

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 reĆ

quirements of Section 73.44 of the Commission's Rules. It is the broadcast station's responĆ

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.

BROADCAST ELECTRONICS, INC.

WARNING WARNING

OPERATING HAZARDS

WARNING

THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT

GROUNDS WITH HIGH AC AND DC POTENTIALS WITH

RESPECT TO THE CABINET WHICH IS AT EARTH POĆ

TENTIAL. DO NOT ENERGIZE THE TRANSMITTER

WITH TEST EQUIPMENT CONNECTED TO THE

TRANSMITTER OUTPUT NETWORK, RF POWER MODĆ

ULE, RF COMBINER, OR POWER SUPPLY COMPOĆ

NENTS.

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 transĆ

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 transĆ

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.

 Broadcast Electronics 1999

Printed in the U.S.A.

-i -

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

-ii -

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

-iii-

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

-iv-

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

-v -

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)

1-1

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 transĆ

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 mod-

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

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.

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

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 indeĆ

pendently quadrature modulated stereo (L-R) information. The results produce a stereo

transmission system compatible with mono receivers.

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

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.

1-2

FIGURE 1-1. AM-2.5E TRANSMITTER

597-1114-1

1-3

597-1114-2

FIGURE 1-2. AM-5E TRANSMITTER

1-4

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

bly. Instrumentation amplifiers provide balanced left and right channel transformerless

audio inputs. The exciter carrier frequency is established by a digital frequency synthesizĆ

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 conĆ

troller circuit board. The controller circuit board consists of CMOS logic control and moniĆ

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 detecĆ

tion circuit operates in association with the power control circuit to foldback the transmitĆ

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. 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 proĆ

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.

1-13. RF POWER MODULE. The AM-2.5E and AM-5E transmitters are equipped with RF powĆ

er modules. A power module is a modular plug-in assembly containing two RF power amĆ

plifier circuit boards and one modulator circuit board. Each power module is equipped

with MOSFET transistors to produce approximately 1375 watts of RF power.

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

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.

1-15. 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 modĆ

ules for control and regulation. A fault detection circuit monitors power supply activity for

failure conditions. A separate modular switching power supply provides operating potenĆ

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 mainĆ

tain on-air operation.

1-5

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

available by local or remote control. Will operate

at a reduced power output (30-50% typical) with

one-half of the power modules.

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.

1-6

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 require-

SUPPRESSION 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.

1-7

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.

1-8

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.

1-9

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.

CUBAGE 42.8Ft3 (1.2 m3).

ENVIRONMENTAL

COOLING

Type Low velocity air with disposable filters.

Requirements - AM2.5E/AM-5E 500 Cubic Feet Per Minute (14.15 m3/min).

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

OPERATING HUMIDITY 0 TO 95% (non-condensing)

1-10

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.

2-1

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. ENVIRONMENTAL REQUIREMENTS.

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

ter installation. Refer to Table 1-2 in SECTION I, INTRODUCTION and ensure the

transmitter is to be installed in an acceptable environment.

2-8. COOLING AIR REQUIREMENTS.

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

adequate air flow. The air must be dry and well filtered. If intake louvers are used, operaĆ

tion of the louvers must be electrically interlocked with the transmitter operation.

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

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 sysĆ

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.

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

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 overĆ

come wind pressures if the duct is vented to the outside.

2-12. PRIMARY POWER.

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

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 installaĆ

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.

2-2

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 shipĆ

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.

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

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 proceĆ

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

SECURELY SEATED INTO THE CONNECTORS.

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.

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

IN DAMAGE TO THE MODULE.

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.

597-1114-7

FIGURE 2-1. AM-2.5E TRANSMITTER INSTALLATION

(2-3/2-4)

597-1114-8

FIGURE 2-2. AM-5E TRANSMITTER INSTALLATION

(2-5/2-6)

2-7

597-1114-27

FIGURE 2-3. TRANSMITTER MOVING

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

ment. If the power supply circuit boards have been removed, locate the shipping container.

Install each circuit board as follows:

CAUTION

THE TRANSMITTER MAY BE DAMAGED IF THE

POWER SUPPLY CONNECTORS ARE NOT SEĆ

CURELY SEATED INTO THE POWER SUPPLY

CIRCUIT BOARD RECEPTACLES.

CAUTION

TO PREVENT DAMAGE TO THE POWER SUPĆ

PLY CIRCUIT BOARD, ENSURE THE CIRCUIT

BOARD IS INSERTED INTO THE MOUNTING

PINS AND THE CAPACITORS ON THE CIRCUIT

SIDE OF THE BOARD ARE PLACED INTO THE

PANEL CUTOUT PRIOR TO SLIDING THE CIRĆ

CUIT BOARD TO SEAT THE MOUNTING SLOTS

INTO THE PINS.

CAUTION

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.

2-8

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

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

2-26. CIRCUIT BOARD PROGRAMMING.

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

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.

2-28. 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.

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

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.

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

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 programĆ

ming is not identical to programming recorded in the factory test data sheets, contact the

Broadcast Electronics Customer Service Department.

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

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

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

synthesizer band of operation. Refer to the factory test data sheets to check the programĆ

ming of the header.

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

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.

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

grammable header J13 control an exciter second order 10 Hz high-pass filter. The high-

pass filter is provided to remove low frequency residual products from specific audio proĆ

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.

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

programmable header J3 control an exciter high frequency boost circuit. The high frequenĆ

cy boost circuit provides increased high frequency response to compensate for a Bessel filĆ

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 reĆ

sponse performance. If the high frequency boost circuit is enabled, the transmitter freĆ

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 reĆ

sponse will decrease approximately 2 dB at 10 kHz and the transient response will imĆ

prove. The high frequency boost circuit is shipped from the factory in the disabled posiĆ

tion.

597-1114-14

FIGURE 2-5. COMPONENT INSTALLATION

(2-9/2-10)

2-11

597-1111-11

FIGURE 2-5. EXCITER CIRCUIT BOARD PROGRAMMING

2-12

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 chanĆ

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 equalĆ

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 bandĆ

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 circuitĆ

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 transĆ

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 transmitĆ

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 operĆ

ate at 5% above the power level 5 output due to the previously retained raise/lower inĆ

formation. The transmitter is shipped with power level trim reset circuit configured to reĆ

set.

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

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 asĆ

signed to an antenna by switch 1 on S1, S2, and S3. Power level 3 is assigned to an antenĆ

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 minĆ

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 interĆ

lock circuit. The circuit can be disabled if the transmitter is to operate into only one antenĆ

na. The transmitter is shipped from the factory with the antenna interlock circuit disĆ

abled.

2-13

597-1111-6

FIGURE 2-6. STEREO CIRCUIT BOARD PROGRAMMING

2-14

597-1112-5

FIGURE 2-7. CONTROLLER CIRCUIT BOARD PROGRAMMING

2-15

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 conĆ

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. ProĆ

gram jumpers P8 and P9 as required.

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

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 reĆ

flected power meter indications.

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

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 forĆ

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 conĆ

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 preĆ

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 difĆ

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

2-16

2-58. REMOTE CONTROL.

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BEĆ

FORE PROCEEDING.

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

trol operations (refer to Figure 2-8 ). The transmitters will interface with almost any reĆ

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 funcĆ

tions and indications. The remote control connections are located at 25-pin D-type conĆ

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 adjustĆ

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 transĆ

mitter off control is located at J1-14. The off indicator will go LOW (0 volts dc) when actiĆ

vated.

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

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 sigĆ

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 loĆ

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 indiĆ

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.

2-17

597-1114-3

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

2-18

597-1114-3A

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

2-19

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 loĆ

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 preĆ

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 indiĆ

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 indiĆ

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 sigĆ

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 cirĆ

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

activate the function.

2-20

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 supĆ

ply emergency condition, or 3) an open interlock condition. A power supply emergency conĆ

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. WIRING.

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

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

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

with electronically balanced 600 Ohm left and right channel audio inputs. The audio inĆ

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 BEĆ

FORE PROCEEDING.

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

ing the cable to the terminals of 9-pin D-type connector J3. J3 is located on the transmitĆ

ter top-panel. To interface audio to the transmitter: 1) use Belden 8760 cable or equivaĆ

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 conĆ

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 transĆ

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. 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 conĆ

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.

2-90. 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 exterĆ

nal interlock.

2-91. MODULATION MONITOR. The modulation monitor connection is located on the transĆ

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

MONITOR SAMPLE OUTPUT receptacle.

2-21

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

597-1114-22

2-22

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BEĆ

FORE PROCEEDING.

WARNING

ENSURE AN EARTH GROUND CONDUCTOR IS SEĆ

CURELY CONNECTED TO THE TRANSMITTER AC

GROUND LUG.

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 disconĆ

nect (refer to Figures 2-10 and 2-11).

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BEĆ

FORE PROCEEDING.

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 comĆ

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

input/control device S1 through a fused service disconnect as shown. Ensure a utility comĆ

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.

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BEĆ

FORE PROCEEDING.

WARNING

ENSURE AN EARTH GROUND CONDUCTOR IS SEĆ

CURELY CONNECTED TO THE TRANSMITTER

GROUND LUG.

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

THE TRANSMITTER SITE LIGHTNING PROTECTION

SYSTEM MUST BE INSPECTED AND IN PROPER

WORKING CONDITION FOR RELIABLE TRANSMITĆ

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 transĆ

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.

2-23

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

597-1114-10

2-24

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

597-1114-9

2-25

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 opĆ

eration. As a general rule: 1) a separation of approximately 0.020 in. for each peak kiloĆ

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 preĆ

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.

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. AdĆ

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 groundĆ

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.

2-26

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

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 inĆ

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

THE TRANSMISSION LINE AND ANTENNA MUST BE

INSPECTED AND IN PROPER WORKING CONDITION

FOR RELIABLE TRANSMITTER OPERATION.

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 transmisĆ

sion line and antenna.

2-113. 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 anĆ

tenna will require the installation of an additional tuning unit to reduce the antenna

VSWR.

2-114. COAXIAL SWITCH CONTROLLER. To prevent damage to the transmitter, the transmitĆ

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.

2-27

FIGURE 2-12. ANTENNA LIGHTNING PROTECTION SYSTEM

597-1111-36

2-28

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 reĆ

place any devices to prevent arcing during peak modulation periods.

2-116. INITIAL CHECKOUT.

WARNING

ENSURE PRIMARY POWER IS DISCONNECTED BEĆ

FORE PROCEEDING.

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. PRELIMINARY OPERATION AND ADJUSTMENT.

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

WARNING

THE TRANSMITTER POWER SUPPLY OPERATES

FROM A HIGH FLOATING GROUND POTENTIAL.

NEVER OPERATE THE TRANSMITTER WITH THE

REARĆDOOR 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.

2-29

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.

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 connecĆ

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 modulaĆ

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.

AM-5E

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

programmed by a jumper on the controller circuit board.

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

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

2-30

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

597-1114-11

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER

BEFORE PROCEEDING.

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 priĆ

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 perĆ

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 measureĆ

ments on the proof of performance sheet at the end of this section.

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER

BEFORE PROCEEDING.

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.

2-31

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 STEĆ

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.

2-32

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 counter-

clockwise.

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 maxi-

mum 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 operĆ

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 conĆ

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 transĆ

mitters operating in the stereo mode, adjust the single channel level control as follows:

597-0095-19

FIGURE 2-15. EQUALIZATION LISSAJOUS PATTERNS

(2-33/2-34)

2-35

WARNING

DISCONNECT ALL TRANSMITTER PRIMARY POWER

BEFORE PROCEEDING.

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 folĆ

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 moniĆ

tor.

3-1

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.

3-2

597-1114-13

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

3-3

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.

3-4

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.

3-5

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 indi-

cator 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 auto-

matic power decrease.

3-6

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 informa-

tion. 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.

597-1114-23

FIGURE 3-2. ECU CONTROLS AND INDICATORS

(3-7/3-8)

3-9

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.

3-10

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 opera-

tion 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.

3-11

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.

597-1112-31

FIGURE 3-3. POWER MODULE CONTROLS AND INDICATORS

3-12

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 TRANSMITĆ

TER AND THE RF DRIVE AND PWM DRIVE INDICAĆ

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 FOLLOWĆ

ING PROCEDURES.

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:

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.

3-13

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

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 cirĆ

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

3-14. TURN OFF.

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

switch/indicator. The transmitter will operate to off.

3-16. METERING.

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

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.

3-18. 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. POWER ADJUST.

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

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 switch to decrease the transmitter output power. Observe

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.

3-14

3-21. MONO/STEREO OPERATION.

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

ing procedures.

3-23. STEREO OPERATION. To configure the transmitter for stereo operations, depress the exĆ

citer mode control switch to illuminate the stereo indicator on the stereo circuit board. In

addition, the ECU front-panel stereo indicator will illuminate.

3-24. 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) automatiĆ

cally configuring the transmitter by removing the stereo circuit board. To configure the

transmitter for mono operations, proceed as follows:

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

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.

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

the transmitter will automatically configure to the monophonic mode when the stereo cirĆ

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, ENĆ

SURE THE TRANSMITTER PRIMARY POWER IS OPERĆ

ATED TO OFF BEFORE REMOVING THE STEREO CIRĆ

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. EXCITER MONITOR OPERATION.

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

the appropriate procedure for the type of monitor function desired.

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

ating mode of the exciter. The MONO indicator will illuminate to indicate when the excitĆ

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.

3-32. 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.

3-15

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. FAULT RESET.

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

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 enĆ

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 cirĆ

cuitry, depress the RESET switch. The fault circuitry will be reset.

3-37. POWER SUPPLY FAULT RESET.

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

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.

3-39. OVER-CYCLE OFF.

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

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.

3-41. OVER-MODULATION PWM MUTE.

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

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.

3-43. TRANSMITTER MONITOR.

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

exciter, 2) the RF power modules, 3) the power supply, 4) the antenna, 5) the remote conĆ

trol, 6) antenna conflict conditions, 7) lightning conditions, 8) interlocks, 9) foldback condiĆ

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. BATTERY TEST.

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

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.

3-16

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 exĆ

citer fault, 3) reflected power emergency conditions, 4) an open remote control fail-safe, or

5) a transmitter mute control signal.

3-49. CONTROLLER REMOTE FAIL-SAFE INDICATOR.

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

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

3-51. EXCITER LOCK INDICATOR.

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

the programmed carrier frequency. The indicator will extinguish when the exciter is unĆ

locked from the programmed carrier frequency.

3-53. EXCITER +5V/+15V/-15V INDICATORS.

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

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.

3-55. STEREO EQUALIZATION INDICATORS.

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

circuit 1 is selected. The stereo circuit board equalization 2 indicator illuminates to indiĆ

cate when equalization circuit 2 is selected.

3-57. RF POWER MODULE INDICATORS.

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

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. POWER SUPPLY INDICATORS.

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

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 indiĆ

cate a failure in a power supply.

3-61. EXCITER NEGATIVE LIMITER INDICATOR.

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

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.

3-63. HIGH/LOW AC LINE CONDITIONS.

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

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.

4-1

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. FUNCTIONAL DESCRIPTION.

4-6. ECU.

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

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.

4-8. 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.

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

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.

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

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.

4-2

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. 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.

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

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.

4-15. 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 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.

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

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.

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

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. 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.

4-19. RF POWER MODULE.

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

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.

597-1114-5

FIGURE 4-1. AM-2.5E BLOCK DIAGRAM

(4-3/4-4)

597-1114-4

FIGURE 4-2. AM-5E BLOCK DIAGRAM

(4-5/4-6)

4-7

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. RF COMBINER.

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

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.

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

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.

4-27. OUTPUT NETWORK.

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

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.

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

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.

4-8

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.

4-9

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. COOLING FANS.

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

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.

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

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

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.

4-46. DETAILED DESCRIPTION.

4-47. POWER SUPPLIES.

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

(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.

4-10

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. ECU POWER SUPPLY ASSEMBLY.

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

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

boards.

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

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.

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

the controller logic for several months. Replace the battery approximately once a year to

ensure proper transmitter operation during ac power failure conditions.

4-57. TRANSMITTER FLUSHING FANS.

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

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

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

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. LOW-VOLTAGE POWER SUPPLY TRANSFORMER.

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

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.

4-62. POWER SUPPLY CIRCUIT BOARD.

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

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.

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

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.

597-1114-6

FIGURE 4-3.

AM-2.5E/AM-5E POWER SUPPLY

SIMPLIFIED SCHEMATIC

(4-11/4-12)

4-13

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.

4-14

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.

4-15

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

4-16

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 B-

leg 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.

4-17

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. 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.

4-99. Left channel audio from the exciter circuit board is applied to the left channel

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.

4-100. The output of each equalization circuit is routed to an equalization and mono/stereo select

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.

4-101. The output of the equalization and mono/stereo select circuits is applied to a summing

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-sideband-

suppressed-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.

4-18

FIGURE 4-4. AM-2.5E/AM-5E RF CIRCUITRY SIMPLIFIED SCHEMATIC (SHEET 1 OF 2) 597-1113-18

597-1113-18A

FIGURE 4-4. AM-2.5E/AM-5E RF CIRCUITRY

SIMPLIFIED SCHEMATIC (SHEET 2 OF 2)

(4-19/4-20)

4-21

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.

4-22

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. 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.

4-112. Forward And Reflected Power Sample Circuit. A voltage sample from the RF output is

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.

4-113. Modulation Monitor Calibration Circuit. A voltage sample for application to the

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.

4-114. A voltage is applied to the modulation monitor receptacle when the power level 5

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. 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.

4-116. LIGHTNING PROTECTION CIRCUIT BOARD. The transmitter is protected from

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.

4-23

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.

4-24

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.

5-1

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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

WITH RESPECT TO THE CABINET WHICH IS AT

EARTH POTENTIAL. DO NOT ENERGIZE THE

TRANSMITTER WITH TEST EQUIPMENT CONĆ

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. FIRST LEVEL MAINTENANCE.

5-7. First level maintenance consists of procedures applied to the equipment to prevent future

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.

5-8. ROUTINE MAINTENANCE.

5-2

WARNING: DISCONNECT POWER PRIOR TO SERVICING

WARNING

NEVER OPEN THE EQUIPMENT UNLESS ALL TRANSĆ

MITTER PRIMARY POWER IS DISCONNECTED. ENĆ

SURE ALL TRANSMITTER PRIMARY POWER IS DISĆ

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. 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.

5-11. 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.

5-12. 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. 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.

5-15. SECOND LEVEL MAINTENANCE.

5-16. Second level maintenance consists of procedures required to adjust the transmitter

circuitry or restore the transmitter to operation after a fault has occurred. The

procedures consist of electrical adjustments, troubleshooting, and component replacement

procedures.

5-3

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-15

FIGURE 5-1. REMOVING THE AIR FILTER

5-4

WARNING: DISCONNECT POWER PRIOR TO SERVICING

WARNING

NEVER OPEN THE EQUIPMENT UNLESS ALL TRANSĆ

MITTER PRIMARY POWER IS DISCONNECTED. ENĆ

SURE ALL TRANSMITTER PRIMARY POWER IS DISĆ

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 TRANSĆ

MITTER PRIMARY POWER IS DISCONNECTED. ENĆ

SURE ALL TRANSMITTER PRIMARY POWER IS DISĆ

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. TRANSMITTER FREQUENCY RE-PROGRAMMING.

5-21. The AM-2.5E/AM-5E transmitters are configured for a specific frequency when shipped

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.

5-22. TROUBLESHOOTING.

5-5

WARNING: DISCONNECT POWER PRIOR TO SERVICING

WARNING

THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT

GROUNDS WITH HIGH AC AND DC POTENTIALS

WITH RESPECT TO THE CABINET WHICH IS AT

EARTH POTENTIAL. DO NOT ENERGIZE THE

TRANSMITTER WITH TEST EQUIPMENT CONĆ

NECTED TO THE TRANSMITTER OUTPUT

NETWORK, RF POWER MODULE, RF COMBINER, OR

POWER SUPPLY COMPONENTS.

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.

TABLE 5-1. AM-2.5E/AM-5E INDICATORS

(Sheet 1 of 4)

ASSEMBLY INDICATOR FUNCTION

ECU ASSEMBLY

TRANSMITTER MONITOR

EXCITER GREEN DISPLAY - Indicates normal exciter

operation.

RED DISPLAY - Indicates no exciter RF drive or

PWM output.

POWER MODULES GREEN DISPLAY - Indicates all RF power modules

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.

POWER SUPPLY GREEN DISPLAY - Indicates normal power supply

operation.

RED DISPLAY - Indicates an open loop or over-

voltage fault in one or more power supply modules.

YELLOW Display - Indicates one or more power

supplies are removed from the transmitter.

5-6

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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

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.

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.

5-7

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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 failĆsafe, an external transmitter mute, lightning,

or high reflected or forward power.

Remote FailĆsafe 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.

5-8

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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 TRANSMITĆ

TER AND THE RF DRIVE AND PWM DRIVE INDICAĆ

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. 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.

5-27. 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.

5-9

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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.

5-10

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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 failĆsafe

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.

5-11

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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.

5-12

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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

5-13

WARNING: DISCONNECT POWER PRIOR TO SERVICING

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.

5-14

WARNING: DISCONNECT POWER PRIOR TO SERVICING

WARNING

MOST SOLVENTS WHICH WILL REMOVE ROSIN FLUX

ARE VOLATILE AND TOXIC BY THEIR NATURE AND

SHOULD BE USED ONLY IN SMALL AMOUNTS IN A

WELL VENTILATED AREA, AWAY FROM FLAME SUCH

AS FROM A SOLDERING IRON OR SMOKING MATERIĆ

ALS. OBSERVE THE MANUFACTURER'S CAUĆ

TIONARY INSTRUCTIONS.

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.

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.

5-15

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-18

FIGURE 5-2. AM-2.5E COMPONENT LOCATOR (SHEET 1 OF 3)

5-16

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-16

FIGURE 5-2. AM-2.5E COMPONENT LOCATOR (SHEET 2 OF 3)

5-17

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-16A

FIGURE 5-2. AM-2.5E COMPONENT LOCATOR (SHEET 3 OF 3)

5-18

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-19

FIGURE 5-3. AM-5E COMPONENT LOCATOR (SHEET 1 OF 3)

5-19

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-24

FIGURE 5-3. AM-5E COMPONENT LOCATOR (SHEET 2 OF 3)

5-20

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-17

FIGURE 5-3. AM-5E COMPONENT LOCATOR (SHEET 3 OF 3)

5-21

WARNING: DISCONNECT POWER PRIOR TO SERVICING

ECU COMPONENT LOCATOR

POWER BLOCK COMPONENT LOCATOR

597-1114-20

FIGURE 5-4. AM-2.5E/AM-5E ECU/POWER BLOCK/OUTPUT NETWORK

ASSEMBLY COMPONENT LOCATOR (SHT 1 OF 2)

5-22

WARNING: DISCONNECT POWER PRIOR TO SERVICING

597-1114-21

FIGURE 5-4. AM-2.5E/AM-5E ECU/POWER BLOCK/OUTPUT NETWORK

ASSEMBLY COMPONENT LOCATOR (SHT 2 OF 2)

AM-2.5E/AM-5E OUTPUT NETWORK ASSEMBLY COMPONENT LOCATOR

6-1

SECTION VI

PARTS LIST

6-1. INTRODUCTION.

6-2. This section provides parts lists for the AM-2.5E/AM-5E transmitter. The parts lists proĆ

vide descriptions and part numbers of electrical components, assemblies, and selected meĆ

chanical parts required for maintenance. Each parts list entry in this section is indexed

by reference designators appearing on the applicable schematic diagrams.

TABLE 6-1. AM-2.5E/AM-5E REPLACEABLE PARTS LIST INDEX (Sheet 1 of 2)

TABLE DESCRIPTION PART NO. PAGE

6-2 AM-2.5E Transmitter 907-2500-100 6-3

6-3 AM-5E Transmitter 907-5000-100 6-3

6-4 AC Sample Circuit Board Assembly 917-0306-007 6-4

6-5 Temperature Sensor Circuit Board Assembly 917-0306-009 6-5

6-6 PFC Relay Board Circuit Board Assembly 917-0330 6-5

6-7 Optically Coupled Relay Circuit Board Assembly 919-0096-001 6-5

6-8 Optically Coupled Relay Circuit Board Assembly 919-0096 6-5

6-9 Harness Assembly 947-0210 6-6

6-10 Power Block Assembly, AM-2.5E 957-0022-021 6-7

6-11 Power Block Assembly, AM-5E 957-0022-051 6-7

6-12 Power Block Motherboard Circuit Board Assembly 917-0303 6-7

6-13 Combiner Circuit Board Assembly, AM-2.5E 917-0321-002 6-7

6-14 Combiner Circuit Board Assembly, AM-5E 917-0321-005 6-7

6-15 Accessory Parts Kit, AM-2.5E 957-0069 6-8

6-16 Accessory Parts Kit, AM-5E 957-0071 6-8

6-17 Frequency Dependant Kit, AM-2.5E, 522 - 650 KHZ 957-0015-121 6-9

6-18 Frequency Dependant Kit, AM-2.5E, 651 - 770 KHZ 957-0015-122 6-9

6-19 Frequency Dependant Kit, AM-2.5E, 771 - 920 KHZ 957-0015-123 6-9

6-20 Frequency Dependant Kit, AM-2.5E, 921 - 1080 KHZ 957-0015-124 6-9

6-21 Frequency Dependant Kit, AM-2.5E, 1081 - 1300 KHZ 957-0015-125 6-9

6-22 Frequency Dependant Kit, AM-2.5E, 1301 - 1580 KHZ 957-0015-126 6-10

6-23 Frequency Dependant Kit, AM-2.5E, 1581 - 1700 KHZ 957-0015-127 6-10

6-24 Frequency Dependant Kit, AM-5E, 522 - 650 KHZ 957-0015-151 6-10

6-25 Frequency Dependant Kit, AM-5E, 651 - 770 KHZ 957-0015-152 6-10

6-26 Frequency Dependant Kit, AM-5E, 771 - 920 KHZ 957-0015-153 6-10

6-27 Frequency Dependant Kit, AM-5E, 921 - 1080 KHZ 957-0015-154 6-11

6-28 Frequency Dependant Kit, AM-5E, 1081 - 1300 KHZ 957-0015-155 6-11

6-29 Frequency Dependant Kit, AM-5E, 1301 - 1580 KHZ 957-0015-156 6-11

6-30 Frequency Dependant Kit, AM-5E, 1581 - 1700 KHZ 957-0015-157 6-11

6-31 Power Block Frequency Dependant Kit, 522 - 650 KHZ 957-1025-061 6-11

6-32 Power Block Frequency Dependant Kit, 651 - 770 KHZ 957-1025-062 6-12

6-33 Power Block Frequency Dependant Kit, 771 - 920 KHZ 957-1025-063 6-12

6-2

TABLE 6-1. AM-2.5E/AM-5E REPLACEABLE PARTS LIST INDEX (Sheet 2 of 2)

TABLE DESCRIPTION PART NO. PAGE

6-34 Power Block Frequency Dependant Kit, 921 - 1080 KHZ 957-1025-064 6-12

6-35 Power Block Frequency Dependant Kit, 1081 - 1300 KHZ 957-1025-065 6-12

6-36 Power Block Frequency Dependant Kit, 1301 - 1580 KHZ 957-1025-066 6-12

6-37 Power Block Frequency Dependant Kit, 1581 - 1700 KHZ 957-1025-067 6-12

6-3

TABLE 6-2. AM-2.5E TRANSMITTER - 907-2500-100

REF. DES. DESCRIPTION PART NO. QTY.

B1, B2 Fan, Patriot, 230 Vac 380-9001 2

C1 Capacitor, 50 uF, 370 Vac, Motor Run 047-5063-370 1

F1, F2 Fuse, 50 Amperes, Dual Element, Time Delay 334-2501 2

F7, F8 Fuse, 3AG, 250V, 2 Amperes 330-0200 2

K2 Contactor, 40 Amperes, 220/240 Vac, 50/60 Hz 341-0076 1

L3, L4 Inductor, 5.8 mH, 30 Amperes 370-2366 2

MOV1 Metal-Oxide Varistor, B40K275, 275V, 1680 Joules 140-0021 1

MOV2 Metal-Oxide Varistor, B40K275, 275V, 1680 Joules 140-0021 1

MOV3 Metal-Oxide Varistor, B40K275, 275V, 1680 Joules 140-0021 1

S1 Switch, Disconnect, Safety Interlock, 60 Amperes 341-0061 1

TB1 Barrier Strip, 9 Terminal 412-0090 1

TB2 Terminal Block, GOULD 63133 412-0050 1

---- Meter, 3.5 Inch (8.89 cm), Taut Band Type, FS = 1 mA dc 310-0068 1

±1%, 35 Ohm Resistance (REFLECTED POWER Meter)

---- Meter, 3.5 Inch (8.89 cm), Taut Band Type, FS = 1 mA dc 310-0069 1

±1%, 35 Ohm Resistance (FORWARD POWER Meter)

---- Filter, RFI, 30 Amperes 339-0030 1

---- Fuseholder, 60 Amperes, 250V, Reject Type 415-0019 1

---- Fuse Holder, AGC 415-2012 2

---- Connector, 7/16 DIN,Panel Jack, Solder 417-0716 1

---- Cable, L5PDF-BH, L5PDR ,17.5", LDF5 610-0009 1

---- Cable, L5PDM, L5PDR, 11.8", LDF5 610-0010 1

---- AC Sample Circuit Board Assembly 917-0306-007 1

---- Temperature Sensor Circuit Board Assembly 917-0306-009 1

---- PFC Relay Board Circuit Board Assembly 917-0330 1

---- Optically Coupled Relay Circuit Board Assembly 919-0096-001 1

---- Harness, AM-2.5E 947-0210 1

---- Exciter/Controller Assembly 957-0009-100 1

---- Power Module Assembly 957-0010-001 2

---- Power Block Assembly 957-0022-021 1

---- Output Network Assembly 957-0068 1

---- Accessory Parts Kit 957-0069 1

---- Power Supply Panel Assembly 957-0315-100 1

TABLE 6-3. AM-5E TRANSMITTER - 907-5000-100

(Sheet 1 of 2)

REF. DES. DESCRIPTION PART NO. QTY.

B1, B2 Fan, Patriot, 230 Vac 380-9001 2

C1, C2 Capacitor, 50 uF, 370 Vac, Motor Run 047-5063-370 2

F1, F2 Fuse, 100 Amperes, Dual Element, Time Delay 334-0002 2

F7 thru F10 Fuse, 3AG, 250V, 2 Amperes 330-0200 4

K2 Contactor, 80 Amperes, 220/240Vac, 50/60 Hz 341-0074 1

6-4

TABLE 6-3. AM-5E TRANSMITTER - 907-5000-100

(Sheet 2 of 2)

REF. DES. DESCRIPTION PART NO. QTY.

L3 thru L6 Inductor, 5.8 mH, 30 Amperes 370-2366 4

MOV1 thru Metal-Oxide Varistor, B40K275, 275V, 1680 Joules 140-0021 3

MOV3

S1 Switch, Disconnect, Safety Interlock, 60 Amperes 341-0061 1

TB1 Barrier Strip, 9 Terminal 412-0090 1

TB2 Terminal Block, GOULD 63133 412-0050 1

---- Meter, 3.5 Inch (8.89 cm), Taut Band Type, FS = 1 mA dc 310-0064 1

±1%, 35 Ohm Resistance (REFLECTED POWER Meter)

---- Meter, 3.5 Inch (8.89 cm), Taut Band Type, FS = 1 mA dc 310-0065 1

±1%, 35 Ohm Resistance (FORWARD POWER Meter)

---- Filter., RFI, 55 Amperes 339-0055 1

---- Fuseholder, 100 Amperes, 250V, Reject Type 415-0020 1

---- Fuse Holder, AGC 415-2012 4

---- Connector, 7/16 DIN,Panel Jack, Solder 417-0716 1

---- Cable, L5PDF-BH, L5PDR ,17.5", LDF5 610-0009 1

---- Cable, L5PDM, L5PDR, 11.8", LDF5 610-0010 1

---- AC Sample Circuit Board Assembly 917-0306-007 1

---- Temperature Sensor Circuit Board Assembly 917-0306-009 1

---- PFC Relay Board Circuit Board Assembly 917-0330 2

---- Optically Coupled Relay Circuit Board Assembly 919-0096-001 1

---- Exciter/Controller Assembly 957-0009-100 1

---- Power Module Assembly 957-0010-001 4

---- Power Block Assembly 957-0022-051 2

---- Output Network Assembly 957-0070 1

---- Accessory Parts Kit 957-0071 1

---- Power Supply Panel Assembly 957-0315-100 2

---- Harness, AM-5E 947-0212 1

TABLE 6-4. AC SAMPLE CIRCUIT BOARD ASSEMBLY - 917-0306-007

REF. DES. DESCRIPTION PART NO. QTY.

C701 Capacitor, Polypropylene Film, .47 uF ±10%, 600V 033-4763 1

D701 thru Diode, 1N4005, Silicon, 600V @ 1 Ampere 203-4005 4

D704

E701, E702 Terminal, Male Disconnect 410-0025 2

J701 Connector, 2-Pin 417-0700 1

R701 thru Resistor, 150 k Ohm±1%, 1/4W 103-1561 6

R706

R707 Resistor, 3.3 Meg Ohm ±5%, 1/4W 100-3373 1

---- Blank, AC Sample Circuit Board 517-0306-007 1

6-5

TABLE 6-5. TEMPERATURE SENSOR CIRCUIT BOARD ASSEMBLY - 917-0306-009

REF. DES. DESCRIPTION PART NO. QTY.

C902 Capacitor, Monolythic Ceramic, 0.1 uF ±10%, 50V 003-1066 1

C906 Capacitor, Monolythic Ceramic, 0.1 uF ±10%, 50V 003-1066 1

C907 Capacitor, Ceramic, 0.001 uF, 1 kV 002-1034 1

J901 Socket, 4-Pin 418-0255 1

R901 Resistor, 10 k Ohm ±1%, 1/4W 100-1051 1

R902 Resistor, 2.21 k Ohm ±1%, 1/4W 103-2241 1

R903 Resistor, 10 k Ohm ±1%, 1/4W 100-1051 1

TP901, Terminal, Turret, Double Shoulder 413-1597 2

TP902

U901 Integrated Circuit, LM35DZ, Celsius Temperature Sensor, 220-0035 1

TO-92 Case

---- Blank, Temperature Sensor, Circuit Board 517-0306-009 1

TABLE 6-6. PFC RELAY BOARD CIRCUIT BOARD ASSEMBLY - 917-0330

REF. DES. DESCRIPTION PART NO. QTY.

J1 Socket, 4-Pin 418-0255 1

J2, J3 Stud, PEM, KFH-832-5ET, PCB Mount 426-8008 2

K1, K2 Relay, SPST, 30 Amperes 270-1213 2

R1 Resistor, 100k Ohm, 2W, ±5% 130-1062 1

---- Blank, PFC Relay Board Circuit Board 517-0330 1

TABLE 6-7. OPTICALLY COUPLED RELAY CIRCUIT BOARD ASSEMBLY - 919-0096-001

REF. DES. DESCRIPTION PART NO. QTY.

---- Optically Coupled Relay Circuit Board Assembly 919-0096 1

DELETE PARTS

C3 Capacitor, Ceramic Disc, 0.1 uF, 600V 000-1051 1

R2 Resistor, 560 Ohm ±5%, 1/2W 110-5633 1

TABLE 6-8. OPTICALLY COUPLED RELAY CIRCUIT BOARD ASSEMBLY - 919-0096

(Sheet 1 of 2)

REF. DES. DESCRIPTION PART NO. QTY.

C1 Capacitor, Ceramic, 0.001 uF, 1 kV 002-1034 1

C2 Capacitor, Electrolytic, 47 uF, 35V 020-4773 1

C3 Capacitor, Ceramic Disc, 0.1 uF, 600V 000-1051 1

C4 Capacitor, Ceramic, 0.001 uF, 1 kV 002-1034 1

D1 Diode, 1N4005, Silicon, 600V @ 1 Ampere 203-4005 1

6-6

TABLE 6-8. OPTICALLY COUPLED RELAY CIRCUIT BOARD ASSEMBLY - 919-0096

(Sheet 2 of 2)

REF. DES. DESCRIPTION PART NO. QTY.

D2 Diode, Zener, 1N5359, 24V ±10%, 5W 200-5359 1

D4 Diode, 1N4005, Silicon, 600V @ 1 Ampere 203-4005 1

D5 Bridge Rectifier, MDA970A3, 4 Amperes, 50-200V 239-0003 1

E1 thru E5 Terminal, Male Disconnect 410-0025 5

F1, F2 Fuse, 3 Amperes, 250V, Printed Circuit Board Mount 330-0055 2

K1 Relay, Printed Circuit Board Mount 270-0054 1

Coil: 24V dc, 660 Ohm ±10%

Contacts: SPST-NO, 0.5 to 15A @ 12 to 240V ac Resistance

MOV1 Varistor, 27V, V27ZA60 140-0023 1

R1 Resistor, 2 k Ohm ±3%, 10W, W/W 130-2032 1

R2 Resistor, 560 Ohm ±5%, 1/2W 110-5633 1

R3 Resistor, 820 Ohm ±5%, 1/2W 110-8233 1

R4 Resistor, 51.1 Ohm ±1%, 1/4W 103-5112 1

R5 Resistor, 2 k Ohm ±3%, 10W, W/W 130-2032 1

U1 Integrated Circuit, 4N33, Optical Isolator, NPN Photo 229-0033 1

Transistor/Infared Emitting Diode Type, 1500V Isolation,

Response: 30 kHz Maximum, Current: 50 mA Maximum,

6-Pin DIP

XU1 Socket, 6-Pin DIP 417-0600 1

---- Blank, Optically Coupled Relay Circuit Board 519-0096 1

TABLE 6-9. HARNESS ASSEMBLY - 947-0210

REF. DES. DESCRIPTION PART NO. QTY.

---- Pins, Connector 417-0036 4

---- Pins, Connector 417-0053 51

---- Pins, Connector 417-0142 42

---- Pins, Socket 417-0143 13

---- Connector Plug, 25-Pin 417-0251 2

---- Receptacle, 15-Pin, D-Type 417-1504 1

---- Kit, Housing, 15-Pin, D-Type 417-1510 1

---- Housing, Wire, MR, Female, 24-Pin, Amp 417-2402 2

---- Kit, Housing, 25-Pin 417-2510 2

---- Plug and Cord ET, AM-500 FAN 417-8500 2

---- 3 Circuit-Commoning Bar, AMP MR 418-0054 2

---- Housing, Connector, 4-Pin 418-0233 1

---- Plug, Housing, 4-Pin 418-0240 3

---- Connector Housing, 6-Pin 418-0670 1

---- Connector Housing, 2-Pin, Female 418-0701 2

---- AC Line Cord, N.E.M.A. 3-Wire North American Plug 682-0001 1

6-7

TABLE 6-10. POWER BLOCK ASSEMBLY, AM-2.5E- 957-0022-021

REF. DES. DESCRIPTION PART NO. QTY.

---- Power Block Motherboard Circuit Board Assembly 917-0303 1

---- Combiner Circuit Board Assembly 917-0321-002 1

TABLE 6-11. POWER BLOCK ASSEMBLY, AM-5E - 957-0022-051

REF. DES. DESCRIPTION PART NO. QTY.

---- Power Block Motherboard Circuit Board Assembly 917-0303 1

---- Combiner Circuit Board Assembly 917-0321-005 1

TABLE 6-12. POWER BLOCK MOTHERBOARD CIRCUIT BOARD ASSEMBLY - 917-0303

REF. DES. DESCRIPTION PART NO. QTY.

C1, C2 Capacitor, Ceramic, Monolythic, .1 uF ±10%, 50V 003-1066 2

C3, C4 Capacitor, Polypropylene Film, 2.2 uF, 400V 030-2256 2

E1, E2, Stud, PEM, KFH-832-8ET, PCB Mount 426-8007 14

E5 thru E8

E11 thru E16

E22, E23

J3 Connector, Male, 24-Pin 417-2401 1

J1A thru J1F Socket, Card Edge, AMP 531353-6 417-0300 6

J2A thru J2F Connector, 15-Pin SUB-D, Female 417-0375 6

T1, T2 Transformer, P.A. Drive, AM-1/5 370-0037 2

---- Blank, Power Block Motherboard Circuit Board 517-0303 1

TABLE 6-13. COMBINER CIRCUIT BOARD ASSEMBLY, AM-2.5E - 917-0321-002

REF. DES. DESCRIPTION PART NO. QTY.

E1 thru E9 Stud, PEM, KFH-832-8ET, Printed Circuit Board Mount 426-8007 9

L1 thru L4 RF Choke Assembly 360-0107 4

T1 thru T4 Combiner Transformer Assembly 370-0060 4

TP1 thru TP10 Terminal Test Point, Oval Red 413-0106 10

---- Blank, Combiner Circuit Board Assembly 517-0321 1

TABLE 6-14. COMBINER CIRCUIT BOARD ASSEMBLY, AM-5E - 917-0321-005

(Sheet 1 of 2)

REF. DES. DESCRIPTION PART NO. QTY.

E1 thru E9 Stud, PEM, KFH-832-8ET, Printed Circuit Board Mount 426-8007 9

L1 thru L4 RF Choke Assembly 360-0107 4

6-8

TABLE 6-14. COMBINER CIRCUIT BOARD ASSEMBLY, AM-5E - 917-0321-005

(Sheet 2 of 2)

REF. DES. DESCRIPTION PART NO. QTY.

T1 thru T4 Combiner Transformer Assembly 370-0061 4

TP1 thru TP10 Terminal, Test Point, Oval, Red 413-0106 10

---- Blank, Combiner Circuit Board 517-0321 1

TABLE 6-15. ACCESSORY PARTS KIT, AM-2.5E - 957-0069

REF. DES. DESCRIPTION PART NO. QTY.

---- Fuse, 3AG, 250V, 2 Amperes 330-0200 2

---- Fuse, 3AB, 15 Amperes, 65V, Very Fast 330-1502 1

---- Fuse, 3AB, 250V, 20 Amperes 330-2000 1

---- Fuse, 30 Amperes, 125V, 1/4x1-1/5850P Lead 334-0030-001 2

---- Fuse, AGC, 1A, 250V, Slow-Blow (for 115 Volt operation) 334-0100 1

---- Fuse, 5 X 20MM, 1.5 Amperes, Slow-Blow 334-1150 2

---- Battery, 9 Volt, Alkaline 350-0002 1

---- Ferrite Core Large AM Transmitter 375-0007-001 2

---- Core, 1.102 OD X .63 ID X .512 THK 375-0009 2

---- Adjustment Tool, Extended and Recessed Flat Blades 407-0186 1

---- Kit, Instruction Manual AM-2.5E/5E 977-1114 1

TABLE 6-16. ACCESSORY PARTS KIT, AM-5E - 957-0071

REF. DES. DESCRIPTION PART NO. QTY.

---- Fuse, 3AG, 250V, 2 Amperes 330-0200 4

---- Fuse, 3AB, 15 Amperes, 65V, Very Fast 330-1502 2

---- Fuse, 3AB, 250V, 20 Amperes 330-2000 2

---- Fuse, 30 Amperes, 125V, 1/4x1-1/5850P Lead 334-0030-001 4

---- Fuse, AGC, 1 Ampere, 250V, Slow-Blow (For 115 Volt Operation) 334-0100 2

---- Fuse, 5 X 20MM, 1.5 Ampere, Slow-Blow 334-1150 4

---- Battery, 9 Volt, Alkaline 350-0002 1

---- Ferrite Core Large AM Transmitter 375-0007-001 2

---- Core, 1.102 OD X .63 ID X .512 THK 375-0009 2

---- Adjustment Tool, extended and recessed flat blades 407-0186 1

---- Kit, Instruction Manual, AM-2.5E/5E 977-1114 1

6-9

TABLE 6-17. FREQUENCY DEPENDANT KIT, AM-2.5E, 522 - 650 KHZ - 957-0015-121

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-001 1

Board, 522 - 650 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 522 - 650 KHZ 957-1025-061 1

---- Kit, Frequency Dependent Parts, Output Network, 522 - 650 KHZ 957-1035-121 1

TABLE 6-18. FREQUENCY DEPENDANT KIT, AM-2.5E, 651 - 770 KHZ - 957-0015-122

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-002 1

Board, 651 - 770 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 651 - 770 KHZ 957-1025-062 1

---- Kit, Frequency Dependent Parts, Output Network, 651 - 770 KHZ 957-1035-122 1

TABLE 6-19. FREQUENCY DEPENDANT KIT, AM-2.5E, 771 - 920 KHZ - 957-0015-123

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-003 1

Board, 771 - 920 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 771 - 920 KHZ 957-1025-063 1

---- Kit, Frequency Dependent Parts, Output Network, 771 - 920 KHZ 957-1035-123 1

TABLE 6-20. FREQUENCY DEPENDANT KIT, AM-2.5E, 921 - 1080 KHZ - 957-0015-124

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-004 1

Board, 921 - 1080 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 921 - 1080 KHZ 957-1025-064 1

---- Kit, Frequency Dependent Parts, Output Network, 921 - 1080 KHZ 957-1035-124 1

TABLE 6-21. FREQUENCY DEPENDANT KIT, AM-2.5E, 1081 - 1300 KHZ - 957-0015-125

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-005 1

Board, 1081 - 1300 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 1081 - 1300 KHZ 957-1025-065 1

---- Kit, Frequency Dependent Parts, Output Network, 1081 - 1300 KHZ 957-1035-125 1

6-10

TABLE 6-22. FREQUENCY DEPENDANT KIT, AM-2.5E, 1301 - 1580 KHZ - 957-0015-126

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-006 1

Board, 1301 - 1580 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 1301 - 1580 KHZ 957-1025-066 1

---- Kit, Frequency Dependent Parts, Output Network, 1301 - 1580 KHZ 957-1035-126 1

TABLE 6-23. FREQUENCY DEPENDANT KIT, AM-2.5E, 1581 - 1700 KHZ - 957-0015-127

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-007 1

Board, 1581 - 1700 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 1581 - 1700 KHZ 957-1025-067 1

---- Kit, Frequency Dependent Parts, Output Network, 1581 - 1700 KHZ 957-1035-127 1

TABLE 6-24. FREQUENCY DEPENDANT KIT, AM-5E, 522 - 650 KHZ - 957-0015-151

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-001 1

Board, 522 - 650 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 522 - 650 KHZ 957-1025-061 1

---- Kit, Frequency Dependent Parts, Output Network, 522 - 650 KHZ 957-1035-151 1

TABLE 6-25. FREQUENCY DEPENDANT KIT, AM-5E, 651 - 770 KHZ - 957-0015-152

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-002 1

Board, 651 - 770 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 651 - 770 KHZ 957-1025-062 1

---- Kit, Frequency Dependent Parts, Output Network, 651 - 770 KHZ 957-1035-152 1

TABLE 6-26. FREQUENCY DEPENDANT KIT, AM-5E, 771 - 920 KHZ - 957-0015-153

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-003 1

Board, 771 - 920 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 771 - 920 KHZ 957-1025-063 1

---- Kit, Frequency Dependent Parts, Output Network, 771 - 920 KHZ 957-1035-153 1

6-11

TABLE 6-27. FREQUENCY DEPENDANT KIT, AM-5E, 921 - 1080 KHZ - 957-0015-154

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-004 1

Board, 921 - 1080 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 921 - 1080 KHZ 957-1025-064 1

---- Kit, Frequency Dependent Parts, Output Network, 921 - 1080 KHZ 957-1035-154 1

TABLE 6-28. FREQUENCY DEPENDANT KIT, AM-5E, 1081 - 1300 KHZ - 957-0015-155

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-005 1

Board, 1081 - 1300 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 1081 - 1300 KHZ 957-1025-065 1

---- Kit, Frequency Dependent Parts, Output Network, 1081 - 1300 KHZ 957-1035-155 1

TABLE 6-29. FREQUENCY DEPENDANT KIT, AM-5E, 1301 - 1580 KHZ - 957-0015-156

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-006 1

Board, 1301 - 1580 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 1301 - 1580 KHZ 957-1025-066 1

---- Kit, Frequency Dependent Parts, Output Network, 1301 - 1580 KHZ 957-1035-156 1

TABLE 6-30. FREQUENCY DEPENDANT KIT, AM-5E, 1581 - 1700 KHZ - 957-0015-157

REF. DES. DESCRIPTION PART NO. QTY.

---- Kit, Frequency Dependent Parts, Power Amplifier Modulator Circuit, 957-1015-007 1

Board, 1581 - 1700 KHZ

---- Kit, Frequency Dependent Parts, Power Block, 1581 - 1700 KHZ 957-1025-067 1

---- Kit, Frequency Dependent Parts, Output Network, 1581 - 1700 KHZ 957-1035-157 1

TABLE 6-31. POWER BLOCK FREQUENCY DEPENDANT KIT, 522 - 650 KHZ -

957-1025-061

REF. DES. DESCRIPTION PART NO. QTY.

L5 thru Coil, 522 - 650 kHz 360-0114-XXX 4

6-12

TABLE 6-32. POWER BLOCK FREQUENCY DEPENDANT KIT, 651 - 770 KHZ -

957-1025-062

REF. DES. DESCRIPTION PART NO. QTY.

L5 thru Coil, 651 - 770 kHz 360-0114-XXX 4

TABLE 6-33. POWER BLOCK FREQUENCY DEPENDANT KIT, 771 - 920 KHZ -

957-1025-063

REF. DES. DESCRIPTION PART NO. QTY.

L5 thru Coil, 771 - 920 kHz 360-0114-XXX 4

TABLE 6-34. POWER BLOCK FREQUENCY DEPENDANT KIT, 921 - 1080 KHZ -

957-1025-064

REF. DES. DESCRIPTION PART NO. QTY.

L5 thru Coil, 921 - 1080 kHz 360-0114-XXX 4

TABLE 6-35. POWER BLOCK FREQUENCY DEPENDANT KIT, 1081 - 1300 KHZ -

957-1025-065

REF. DES. DESCRIPTION PART NO. QTY.

L5 thru Coil, 1081 - 1300 kHz 360-0114-XXX 4

TABLE 6-36. POWER BLOCK FREQUENCY DEPENDANT KIT, 1301 - 1580 KHZ -

957-1025-066

REF. DES. DESCRIPTION PART NO. QTY.

L5 thru Coil, 1301 - 1580 kHz 360-0114-XXX 4

L9 Inductor, 120 uH, 1.5 Amperes ±10% 360-1824 1

TABLE 6-37. POWER BLOCK FREQUENCY DEPENDANT KIT, 1581 - 1700 KHZ -

957-1025-067

REF. DES. DESCRIPTION PART NO. QTY.

L5 thru Coil, 1581 - 1700 kHz 360-0114-XXX 4

L9 Inductor, 100 uH, 1.5 Amperes ±10% 360-1823 1

7-1

SECTION VII

DRAWINGS

7-1. INTRODUCTION.

7-2. This section provides schematic diagrams and assembly diagrams as indexed below for the

Broadcast Electronics AM-2.5E/AM-5E transmitters.

FIGURE TITLE NUMBER

7-1 OVERALL SCHEMATIC DIAGRAM, AM-2.5E SB907-2500-100

7-2 SCHEMATIC DIAGRAM, TEMPERATURE SENSOR SA917-0306-009

CIRCUIT BOARD

7-3 SCHEMATIC DIAGRAM, AC SAMPLE CIRCUIT BOARD SA917-0306-007

7-4 ASSEMBLY DIAGRAM, ECU DISPLAY CIRCUIT AD917-0306-001/

BOARD -002/-003/-004/

-005/-006/-007/

-009/-014

7-5 SCHEMATIC DIAGRAM, POWER BLOCK MOTHERBOARD SB917-0303

7-6 ASSEMBLY DIAGRAM, POWER BLOCK MOTHERBOARD AC917-0303

7-7 ASSEMBLY DIAGRAM, COMBINER AC917-0321/-001

-006

7-8 SCHEMATIC DIAGRAM, OPTICALLY COUPLED RELAY SB919-0096/-001

7-9 ASSEMBLY DIAGRAM, OPTICALLY COUPLED AB919-0096/-001

RELAY (OCR)

7-10 SCHEMATIC DIAGRAM, CUSTOMER INTERFACE PRINTED SD917-0410

CIRCUIT BOARD

7-11 ASSEMBLY DIAGRAM, CUSTOMER INTERFACE PRINTED AB917-0410

CIRCUIT BOARD

7-12 SCHEMATIC DIAGRAM, POWER FACTOR CORRECTOR BOARD SB917-0330

7-13 ASSEMBLY DIAGRAM, POWER FACTOR CORRECTOR BOARD AB917-0330

7-14 SCHEMATIC DIAGRAM, INTERFACE CIRCUIT BOARD, AM-5E SB917-0306-003

7-15 SCHEMATIC DIAGRAM, POWER SUPPLY STATUS SA917-0306-006

CIRCUIT BOARD, AM-5E

TABLE OF CONTENTS

PARAGRAPH PAGE NO.

SECTION I POWER SUPPLY THEORY OF OPERATION

1-1 Introduction 1-1

1-3 General Description 1-1

1-6 AC Input 1-1

1-8 Conventional Rectifier Circuitry 1-1

1-10 Soft-Start Circuit 1-1

1-12 AC Line Detection/Synchronization 1-2

1-16 Soft-Start Control Circuit 1-2

1-18 Power Factor Corrector Circuit Board Control Circuit 1-2

1-20 SCR Controlled Rectifier Circuit 1-5

1-23 Filter Circuit 1-5

1-25 Power Supply Enable Circuit 1-5

1-28 Switching Regulator Circuit 1-5

1-30 Low Voltage Power Supply 1-6

1-31 Switching Regulator Control Circuit 1-6

1-33 Switching Regulator Circuit Operation 1-6

1-34 Power Control/Correction Circuit 1-6

1-38 Fault Detection 1-7

1-43 Crowbar Circuit 1-7

1-47 Power Supply Circuit Grounds 1-8

SECTION II POWER SUPPLY CIRCUIT BOARD MAINTENANCE

2-1 Introduction 2-1

2-3 Safety Considerations 2-1

2-6 First Level Maintenance 2-1

2-8 Cleaning and Inspection 2-1

2-10 Second Level Maintenance 2-2

2-12 Troubleshooting 2-2

2-13 Safety Considerations 2-2

2-14 Removing/Installing a Power Supply Circuit Board 2-2

2-17 Troubleshooting Procedures 2-3

2-18 Component Replacement Procedure 2-4

SECTION III POWER SUPPLY CIRCUIT BOARD PARTS LIST

3-1 Introduction 3-1

SECTION IV POWER SUPPLY CIRCUIT BOARD DRAWINGS

4-1 Introduction 4-1

LIST OF ILLUSTRATIONS

FIGURE TITLE PAGE NO.

1-1 POWER SUPPLY CIRCUIT BOARD 1-3

SIMPLIFIED SCHEMATIC

LIST OF TABLES

TABLE TITLE PAGE NO.

2-1 POWER SUPPLY MODULE TROUBLESHOOTING 2-3

3-1 REPLACEABLE PARTS LIST INDEX 3-1

1-1

SECTION I

POWER SUPPLY THEORY OF OPERATION

1-1. INTRODUCTION.

1-2. This section presents a general description of the Broadcast Electronics AM-2.5E/AM-5E

transmitter power supply assembly.

1-3. GENERAL DESCRIPTION.

1-4. DC operating potentials for the RF power modules are provided by power supply assemĆ

blies (refer to Figure 1-1). The power supply assembly consists of: 1) a power supply cirĆ

cuit board and 2) filter and transformer components located on a power supply panel.

One power supply assembly provides dc operating potentials for one power block. The

AM-2.5E transmitter is equipped with 1 power supply assembly. The AM-5E transmitter

is equipped with 2 power supply assemblies.

1-5. The modular design of the power supply assembly allows the power supply circuit board

to be removed from the transmitter for maintenance. The following text presents a deĆ

scription of the power supply circuit board and the components located on the power sup-

ply panel assembly.

1-6. AC INPUT.

1-7. AC power from the ac input switch is applied through fuses F6 and F7 to power trans-

former T1. Fuses F6 and F7 protect the circuitry from over-current conditions. TransĆ

former T1 consists of: 1) a single primary winding and 2) five secondary windings. The

transformer is designed to provide low-voltage ac samples for application to five convenĆ

tional bridge rectifier circuits.

1-8. CONVENTIONAL RECTIFIER CIRCUITRY.

1-9. AC power from a 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 pow-

er module power amplifier circuit boards. Capacitor C21 provides filtering for the supply.

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 the power supply circuit

board circuitry. Capacitor C20 provides filtering for the supply. AC power from a third

winding of ac power transformer T1 is applied to bridge rectifier D9. D9 rectifies the ac

potential into an unregulated +20 volt dc supply for application to: 1) the modulator cir-

cuit 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. 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 sup-

ply 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. An ac sample

from the winding is routed for application to a soft-start circuit. Capacitor C15 provides

filtering for the supply.

1-10. SOFT-START CIRCUIT.

1-11. An ac sample from the winding of T1 is also routed to a soft-start circuit. The soft-start

circuit is designed to eliminate component stress during turn-on by limiting the current

in-rush. The circuit consists of an ac line detection/synchronization and soft-start control

circuits.

1-2

1-12. AC LINE DETECTION/SYNCHRONIZATION. An ac sample from a winding of transformĆ

er T1 is rectified by diodes D7 and D8 and applied to integrated circuit U6B. U6B funcĆ

tions as a zero phase detector. As the ac line phase approaches zero degrees, U6B will

output a HIGH pulse. The HIGH pulse is applied to: 1) transistor Q2, 2) transistor Q7 of

the soft-start circuit, and 3) ac line detector U5A/U5B. The pulse biases transistor Q2

and optical coupler U2 on. Q2 and U2 will output a pulse each time the ac line phase is

zero. As a result, U2 will output a 120 Hz signal to the controller circuit board.

1-13. U5A and U5B function as an ac line voltage detector. When ac line voltage is present,

U5A will output a LOW. The LOW allows transistor Q3 to be biased on. With Q3 on, a

+12 volt dc signal is applied to optical coupler U1. When a power supply enable and a

PWM OK signal is applied to U1, U1 will output a reference voltage to a soft-start control

circuit for power supply operation. When ac line voltage is not present, U5A will output a

HIGH, the HIGH biases transistor Q3 off to terminate power supply operation. When ac

power is re-applied, U5B will maintain a HIGH for 100 milliseconds to allow the circuit to

stabilize during turn-on operations.

1-14. In addition to the ac line voltage detection circuit, integrated circuit U6A functions as a

low line voltage detector. When the dc supply is above the threshold at U6A, U6A will

output a LOW to bias transistor Q1 off. As a result, a HIGH ac OK signal indicating acĆ

ceptable ac line voltage is applied to optical coupler U9. When the dc supply is below 185

volts, U6A will output a HIGH to bias transistor Q1 on. As a result, a LOW ac OK signal

indicating low ac line voltage is applied to optical coupler U9. When the voltage increases

to approximately 190 volts, the output of U6A will go LOW to enable the power supply.

1-15. This circuit is also used to detect high ac line voltage potentials. If the ac line voltage is

above approximately 270 volts, transistor Q28 will be biased on. With Q28 on, the input

to U6A will be muted. When the input is muted: 1) the transmitter output power will be

muted and 2) no transmitter fault or emergency condition will be generated.

1-16. SOFT-START CONTROL CIRCUIT. The soft-start control circuit consists of: 1) transistors

Q4 through Q9 and 2) integrated circuit U7. The circuit is designed to generate short

duration pulses in each time the ac line waveform crosses the 0 volt axis. The pulses are

applied to an SCR controlled rectifier 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.

1-17. The circuit generates the soft-start pulses from two signals: 1) a ramp signal and 2) a

triangle signal. The ramp signal is generated by transistors Q4 and Q5. When ac line

voltage is detected, a +12 volt signal from U1 is applied to transistor Q4. Q4 operates in

association with capacitor C16 and transistor Q5 to generate a ramp voltage. The

triangle signal is generated by transistors Q6 and Q7. Pulses from U6B are applied to

transistor Q7. Q7 operates in association with capacitor C17 and transistor Q6 to gener-

ate a triangle signal. The triangle signal and the ramp signal are applied to comparator

U7. U7 responds by generating a square-wave signal with a short duty cycle when the ac

line phase is zero. The square-wave signal from U7 is applied to soft-start driver transisĆ

tors Q8 and Q9. Q8 and Q9 will slowly bias the rectifier circuit on to limit the current

in-rush.

1-18. POWER FACTOR CORRECTOR CIRCUIT BOARD CONTROL CIRCUIT.

1-19. Transistors Q26 and Q27 control a power factor corrector circuit board. During soft-start

operation, ramp voltage will drop below approximately 3V. When this occurs, the output

of transistor Q26 will go LOW. This LOW biases transistor Q27 on. With Q27 on, a LOW

energizes two relays on the power factor corrector circuit board. With the relays ener-

gized, a capacitor is inserted into the circuit to enable power factor correction.

597-1112-28A

FIGURE 1-1. POWER SUPPLY CIRCUIT BOARD

SIMPLIFIED SCHEMATIC

(1-3/1-4)

1-5

1-20. SCR CONTROLLED RECTIFIER CIRCUIT.

1-21. The ac line voltage is rectified into a main dc supply for the modulator and amplifier cirĆ

cuitry by an SCR controlled bridge rectifier circuit. Primary ac power for the main dc

supply is applied to fuses F1 and F2. The fuses protect the power supply circuitry from

over-current conditions. Metal-Oxide-Varistor MOV1 prevents damage to the rectifier

circuitry from ac line voltage surge potentials.

1-22. The SCR controlled rectifier circuit consists of diodes D15 through D17 and SCRs D13

and D14. The rectifier circuit is controlled by the soft-start control circuit. When power

is required from the circuit, the soft-start circuit will output synchronized ac line pulses

to SCRs D13 and D14. The SCRs will respond by slowly biasing the rectifier circuit on.

The rectifier will output an unregulated and unfiltered dc supply at a maximum of 300V

to an inductor and capacitor filter network located on the power supply panel.

1-23. FILTER CIRCUIT.

1-24. The output of the rectifier circuit is applied to a filter network consisting of capacitors C24

through C27. The filter is designed to remove the ripple in the supply. The output of the

capacitor network generates the positive leg of the B supply. The B supply is the main

operating supply for the RF power modules. The negative leg of the B supply is generated

by a switching regulator circuit (refer to the following text).

1-25. POWER SUPPLY ENABLE CIRCUIT.

1-26. The power supply is controlled by a: 1) power supply enable signal from the controller

and 2) power supply mute signal from the modulator circuit boards. When power supply

operation is required, the controller will output a LOW power supply enable signal to optiĆ

cal coupler U8. With no mute signals present, U8 will output a HIGH to AND gate U12A.

With a HIGH ac OK signal from U9 indicating the presence of ac power and no power

supply faults, U12A will output a HIGH to U12B. With a HIGH from U21A/U21B, U12B

will output a HIGH to U12C and to Q12. With a HIGH from U14 indicating the crowbar

circuit is off, U12C will output a HIGH after a one second delay to: 1) transistor Q10,

2) AND gate U12D, and 3) NAND gate U21C. The HIGH biases Q12 and U15 on to dis-

able the crowbar circuit. Q10 will respond by routing a HIGH power supply enable signal

to optical coupler U1. U1 will output a dc voltage to enable the power supply soft-start

circuit. AND gate U12D will output a HIGH to transistor Q11. The HIGH biases Q11 on

to enable regulator controller U13 and bias Q13 off.

1-27. When a power supply mute operation is required, an RF power module modulator circuit

board will output a mute signal to optical coupler U8. U8 will output a LOW to AND gate

U12A. With a HIGH ac OK signal from U9, U12A will output a LOW to U12B. U12B will

output a LOW to U12C and to Q12. The LOW biases Q12 and U15 off to enable the crowĆ

bar circuit. U12C will output a LOW to: 1) transistor Q10, 2) AND gate U12D. Q10 will

be biased off to terminate power supply operation by disabling the drive to the SCR recti-

fier circuit. U12D will disable Q11 which allows a HIGH to disable regulator controller

U13 and bias Q13 on. Q13 will output a LOW to disable the fault detection circuit to preĆ

vent erroneous fault indications during mute conditions.

1-28. SWITCHING REGULATOR CIRCUIT.

1-29. The B supply is regulated and controlled by a switching regulator circuit. The switching

regulator circuit generates the - leg of the B supply and consists of: 1) a low voltage pow-

er supply circuit, 2) a power control network, 3) optical coupler U17, 4) inverting buffer

U19, and 5) switching regulator transistors Q21 and Q22.

1-6

1-30. LOW VOLTAGE POWER SUPPLY. A dc operating supply for the optical couplers and the

inverting buffers is generated by bridge rectifier D25. D25 full-wave rectifies an ac po-

tential from ac transformer T1 into an unregulated +20V supply. The supply is applied to

+18V regulator U16. The output of U16 is further regulated to a 5V operating potential

by a resistive divider and a zener diode. The 5V supply is applied to optical coupler U17

and buffer U19.

1-31. SWITCHING REGULATOR CONTROL CIRCUIT. The switching regulator circuit is conĆ

trolled by: 1) regulator controller U13 and 2) a power control/correction circuit. The cirĆ

cuits function in a closed-loop to control the operation of the switching regulator. As a

result, the regulator outputs a precision dc operating voltage at the appropriate level for

application to the RF power modules.

1-32. Integrated circuit U13 functions as the switching regulator controller. U13 is a PWM outĆ

put device 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 voltage correction cirĆ

cuit. With a correction voltage present at U13, U13 will output a PWM square wave sig-

nal to optical coupler U17. U17 provides isolation for the transition of the signal from two

different circuit ground potentials. The output of coupler U17 is inverted by inverting

buffer U19.

1-33. SWITCHING REGULATOR CIRCUIT OPERATION. The PWM output of U19 is applied to

the gates of IGBT (insulated-gate-bipolar-transistor) switching regulator transistors Q21

and Q22. The transistors function to regulate the negative leg of the B supply. The out-

put 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. Capacitor C55 provides filtering for the negative leg of the B supply.

The output of the regulator circuit (B- leg) is applied to circuitry on the modulator circuit

board.

1-34. POWER CONTROL/CORRECTION CIRCUIT.

1-35. The switching regulator output voltage is controlled by a PWM (pulse-width-modulated)

signal from the controller. The PWM signal is a 1 kHz square-wave signal with a duty

cycle which varies in response to different power levels. The PWM signal from the con-

troller is applied to optical coupler U22. With a +5 volt signal from the motherboard, U22

will output the PWM signal to transistors Q17 and Q18. Q17 will discharge capacitor C63

when a 1 kHz control signal is present. C63 will output a LOW PWM OK signal to optical

coupler U1. Q18 inverts the power control PWM signal. The output of Q18 is applied

through buffer U24C to a low-pass filter consisting of: 1) resistors R115, R116, and R117

and 2) capacitors C75, C76, and C77. The filter converts the power control PWM square-

wave signal into a dc control voltage. The voltage is routed through buffer U24A to U24B.

1-36. U24B functions as a current feedback loop filter. U24B differentially amplifies the dc conĆ

trol voltage and a current sample from the switching regulator output filter capacitor. As

a result, U24B produces a dc control voltage for application to U24D.

1-37. U24D functions as a voltage feedback loop filter. U24D differentially amplifies the control

voltage from U24B and a voltage sample from the B+ leg of the supply. As a result,

U24D produces a dc control voltage for application to: 1) switching regulator controller

U13 and 2) a fault detection circuit. U13 will respond to the correction voltage by chang-

ing the duty cycle of the PWM drive signal to optical coupler U17. The switching regula-

tor circuit will respond by changing the output voltage to a level required by the power

control PWM signal.

1-7

1-38. FAULT DETECTION.

1-39. A fault detection circuit monitors the regulator for four conditions: 1) over-voltage,

2) open-loop, 3) over-current, and 4) over temperature. Over-voltage conditions are

monitored by U23A. U23A compares a sample of the B+ leg to a reference voltage. When

the B+ sample exceeds the reference voltage, the output of U23A will go LOW. The LOW

is routed to fault detector latch U21A/U21B. Open-loop conditions are monitored by

U23B. U23B compares a correction voltage sample to a reference voltage. When the

correction voltage sample exceeds the reference, the output of U23B will go LOW. The

LOW is inverted at U21D and applied to NAND gate U21C. With a HIGH power supply

enable signal from U12C, U21C will output a LOW to fault detector latch U21A/U21B.

1-40. Over-current conditions are monitored by transistors Q19 and Q20. When an over-curĆ

rent condition occurs, Q19 and Q20 will output a LOW. The LOW is routed to fault detecĆ

tor latch U21A/U21B. Over-temperature conditions are monitored by temperature sensor

U25. When the power supply temperature exceeds 72 degrees C, U25 will output a LOW

through transistor Q25 to U21D. The LOW is inverted at U21D and applied to NAND

gate U21C.

1-41. With a LOW from U21C or U23A, latch U21A/U21B will: 1) output a HIGH to transistor

Q16 and 2) output a LOW to transistor Q15 and to U12B. Transistor Q16 will be biased

on and will output a LOW to enable optical coupler U11. U11 will respond by generating

a power supply fault signal. AND gate U12B will output a LOW to: 1) disable regulator

controller U13, 2) disable the SCR controlled rectifier circuit, and 3) initiate a logic seĆ

quence to enable the crowbar circuit (refer to the following text). Transistor Q15 will be

biased off and will disable optical coupler U10. The output of U10 will open.

1-42. The output of U10 is connected in parallel with U10 on each power supply circuit board.

When the output of U10 on each power supply circuit board is open, a HIGH power sup-

ply emergency signal to be applied to the controller. The power supply emergency signal

indicates all power supply modules contain fault conditions.

1-43. CROWBAR CIRCUIT.

1-44. The power supply circuit board is equipped with a crowbar circuit to discharge the B supĆ

ply during power supply off, ac off, and power supply mute conditions. The crowbar cir-

cuit consists of: 1) crowbar MOSFET Q23 and 2) resistor R72. Control of the circuit is

provided by logic gates which monitor power supply off, ac off, and power supply mute

conditions.

1-45. During a power supply off, ac off, or power supply mute condition, AND gate U12A will

output a LOW to U12B. With a HIGH from U21A/U21B, U12B will output a LOW to

transistor Q12. The LOW biases Q12 and optical coupler U15 off. As a result, a HIGH is

applied to the gate of crowbar MOSFET Q23. The HIGH biases Q23 on to short the B

supply and discharge capacitors C24, C25, C26, C27 and C55. Resistor R72 limits the curĆ

rent during shorting operations.

1-46. When U15 is biased off, optical coupler U14 will also be disabled. With U14 disabled, a

LOW is applied to U12C. U12C will output a LOW to disable the PWM drive to the

switching regulator circuit.

1-8

1-47. POWER SUPPLY CIRCUIT GROUNDS.

1-48. The power supply circuit board is equipped with three isolated circuit grounds: 1) 0VS,

2) 0VP, and 3) 0VI. The circuit grounds are at different potentials and are not referenced

to earth ground. The 0VS ground is the circuit ground for the: 1) SCR controlled bridge

rectifier circuit, 2) soft-start control circuit, 3) ac line voltage detector circuit, and 4) low-

voltage detection circuit. The 0VP circuit ground is used to create the negative leg of the

B supply. The 0VI ground is the circuit ground for the: 1) crowbar circuit, 2) switching

regulator circuit, 3) inverting drive buffers, and 4) switching regulator transistors. The

circuit grounds are used in association with the circuitry to generate the operating volt-

ages for the RF power modules.

2-1

WARNING: DISCONNECT POWER PRIOR TO SERVICING

SECTION II

POWER SUPPLY CIRCUIT BOARD MAINTENANCE

2-1. INTRODUCTION.

2-2. This section provides maintenance information for the AM-2.5E/AM-5E transmitter

power supply circuit board assembly.

2-3. SAFETY CONSIDERATIONS.

WARNING

THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT

GROUNDS WITH HIGH AC AND DC POTENTIALS

WITH RESPECT TO THE CABINET WHICH IS AT

EARTH POTENTIAL. DO NOT ENERGIZE THE

TRANSMITTER WITH TEST EQUIPMENT CONĆ

NECTED TO THE TRANSMITTER OUTPUT

NETWORK, RF POWER MODULE, RF COMBINER, OR

POWER SUPPLY COMPONENTS.

2-4. 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.

2-5. In addition to high voltages and currents, the transmitters contain multiple circuit