OUS425A500-watt solid state television transmitter

ADC-425A Type Acceptance Report Users Manual April 20005-1 5. USER’S MANUAL The user’s manual for the ADC-425A system is provided as separate Word and PDF files.

500-Watt VHF Transmitter Table of Contents 425A, Rev. 0i TABLE OF CONTENTS CHAPTER 1 INTRODUCTION 1.1 Manual Overview ..................................................................................1-1 1.2 Assembly Designation Procedure ............................................................1-1 1.3 Safety .................................................................................................1-1 1.4 Maintenance.........................................................................................1-2 1.5 Material Return Procedure......................................................................1-2 1.6 Warranty for Broadcast Products – Limited One-Year Warranty ..................1-3 CHAPTER 2 SYSTEM DESCRIPTION 2.1 System Overview..................................................................................2-1 2.2 Control and Status ................................................................................2-2 2.2.1 VHF Exciter Tray ..........................................................................2-3 2.2.2 600-Watt Amplifier Tray ...............................................................2-6 2.3 Input and Remote Connections...............................................................2-7 2.4 AC Input ............................................................................................2-10 CHAPTER 3 CIRCUIT DESCRIPTIONS 3.1 High-Band VHF Exciter ...............................................................................3-1 3.1.1 Aural IF Synthesizer Board, 4.5 MHz ...................................................3-1 3.1.2 Sync Tip Clamp/Modulator Board........................................................3-2 3.1.3 Delay Equalizer Board .......................................................................3-5 3.1.4 IF Carrier Oven Oscillator Board .........................................................3-6 3.1.5 ALC Board, NTSC ..............................................................................3-7 3.1.6 IF Phase Corrector Board ................................................................. 3-13 3.1.7 VHF Mixer/Amplifier Enclosure Assembly ........................................... 3-15 3.1.8 Transmitter Control Board................................................................ 3-17 3.1.9 Visual/Aural Metering Board............................................................. 3-22 3.1.10 Channel Oscillator Assembly, Dual Oven .......................................... 3-23 3.1.11 EEPROM FSK Identifier Board ......................................................... 3-23 3.1.12 IF Attenuator Board....................................................................... 3-24 3.2 600-Watt High-Band VHF Amplifier Trays.................................................... 3-24 3.3 Bandpass Filter Assembly ......................................................................... 3-28 CHAPTER 4 INSTALLATION AND SETUP PROCEDURES 4.1 Site Considerations ...............................................................................4-1 4.2 Unpacking the Cabinets and Trays ..........................................................4-4 4.3 Installing the Cabinets and Trays............................................................4-5 4.4 Setup and Operation .............................................................................4-6 CHAPTER 5 DETAILED ALIGNMENT PROCEDURES 5.1 High-Band VHF Exciter Tray with Baseband Video and Audio Inputs............5-1 5.2 VHF Exciter Tray with 4.5-MHz Composite Input Kit ..................................5-1 5.3 VHF Exciter Tray with Either Baseband or 4.5-MHz Composite Input ...........5-2 5.4 IF Phase Corrector Adjustment ...............................................................5-3 5.5 Linearity Corrector Adjustment ...............................................................5-3 5.6 Phase and Gain Adjustment of the VHF Amplifier Trays .............................5-4 500-Watt VHF Transmitter Table of Contents 425A, Rev. 0ii TABLE OF CONTENTS (continued) 5.7 Calibration of the Forward Output Power Level of the Transmitter...............5-5 5.8 Calibration of the Reflected Output Level of the Transmitter.......................5-5 5.9 2-Way Combiner Assembly ....................................................................5-6 5.10 Bandpass Filter Assemblies ..................................................................5-6 5.11 600-Watt High-Band VHF Amplifier Tray ................................................5-6 5.11.1 AGC Control Board .....................................................................5-6 5.11.2 Phase Shifter Board....................................................................5-7 5.11.3 VHF Filter/Amplifier Board...........................................................5-7 5.11.4 High-Band VHF Amplifier Board ...................................................5-7 5.11.5 Overdrive Protection Board .........................................................5-7 5.11.6 VHF High-Band Amplifier Board ...................................................5-7 5.11.7 4-Way Splitter Board ..................................................................5-8 5.11.8 High-Band Amplifier Board ..........................................................5-8 5.11.9 4-Way Combiner Board...............................................................5-8 5.11.10 Calibration of the Visual Plus Aural Output Power and VSWR Cutback.........................................................5-8 5.12 Board Level Alignment Procedures ........................................................5-9 5.12.1 (Optional) 4.5-MHz Composite Input Kit .......................................5-9 5.12.2 Delay Equalizer Board...............................................................5-10 5.12.3 Composite 4.5-MHz Filter Board.................................................5-10 5.12.4 (Optional) 4.5-MHz Bandpass Filter Board...................................5-10 5.12.5 IF Carrier Oven Oscillator B…

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500-Watt VHF Transmitter Chapter 1, Introduction 425A, Rev. 01-1 Chapter 1 Introduction This manual explains the installation, setup, alignment, and maintenance procedures for the 425A 500-watt solid state VHF transmitter. It is important that you read all of the instructions, especially the safety information in this chapter, before you begin to install or operate the unit. 1.1 Manual Overview This instruction manual is divided into five chapters and supporting appendices. Chapter 1, Introduction, contains information on the assembly numbering system used in the manual, safety, maintenance, return procedures, and warranties. The second chapter describes the transmitter and includes discussions on system control and status indicators and remote control connections. Chapter 3 contains a detailed discussion of the circuits and boards that make up the 425A transmitter. Chapter 4 explains how to unpack, install, setup, and operate the transmitter. Chapter 5, Detailed Alignment Procedures, provides information on adjusting the system to achieve peak operation of the assemblies. The appendices contain a sample log sheet, assembly and subassembly drawings, and system specifications. 1.2 Assembly Designation Procedure ADC has assigned assembly numbers, such as Ax (x=1,2,3...), to all assemblies, trays, and boards that are referenced in the text of this manual and shown on the block diagrams and interconnect drawings provided in the appendices. These supporting documents are arranged in increasing numerical order in the appendices. Section titles in the text for assembly or tray descriptions or alignment procedures also indicate the associated drawing(s) and the relevant appendix that contains the drawing. Sections describing vendor-supplied items, such as meters and power supplies, do not contain this information. 1.3 Safety The VHF transmitters manufactured by the Broadcast Systems Division of ADC are designed to be easy to use and repair while providing protection from electrical and mechanical hazards. Listed throughout the manual are notes, cautions, and warnings concerning possible safety hazards that may be encountered while operating or servicing the transmitter. Please review these warnings and familiarize yourself with the operation and servicing procedures before working on the transmitter. Read All Instructions – All of the operating and safety instructions should be read and understood before operating this equipment. Retain Manuals – The manuals for the transmitter should be retained at the transmitter site for future reference. We provide two sets of manuals for this purpose; one set can be left at the office while one set can be kept at the site. Heed all Notes, Warnings, and Cautions – All of the notes, warnings, and cautions listed in this safety section and throughout the manual must be followed. Follow Instructions – All of the operating and use instructions for the transmitter should be followed. Cleaning – Unplug or otherwise disconnect all power from the equipment before cleaning. Do not use liquid or aerosol cleaners. Use a damp cloth for cleaning. 500-Watt VHF Transmitter Chapter 1, Introduction 425A, Rev. 01-2 Ventilation – Openings in the cabinets and tray front panels are provided for ventilation. To ensure reliable operation of the transmitter, and to protect the unit from overheating, these openings must not be blocked. Servicing – Do not attempt to service this product yourself until becoming familiar with the equipment. If in doubt, refer all servicing questions to qualified ADC service personnel. Replacement Parts – When replacement parts are used, be sure that the parts have the same functional and performance characteristics as the original part. Unauthorized substitutions may result in fire, electric shock, or other hazards. Please contact the ADC Technical Service Department if you have any questions regarding service or replacement parts. 1.4 Maintenance The 425A is designed with components that require little or no periodic maintenance except for the routine cleaning of the fans and the front panels of the trays. The amount of time between cleanings depends on the conditions within the transmitter room. While the electronics have been designed to function even if covered with dust, a heavy buildup of dust, dirt, or insects will affect the cooling of the components. This could lead to a thermal shutdown or premature failure of the affected trays. When the front panels of the trays become dust covered, the top covers should be removed and any accumulated foreign material should be removed. A vacuum cleaner, utilizing a small wand- type attachment, is an excellent way to suction out the dirt. Alcohol and other cleaning agents should not be used unless you are certain that the solvents will not damage components or the silk- screened markings on the trays and boards. Water-based cleaners can be used, but do not saturate the components. The fans and heatsinks should be cleaned of all dust or dirt to permit the free flow of air for cooling purposes. It is recommended that the operating parameters of the transmitter be recorded from the meters on the trays and the system metering control panel at least once a month. It is suggested that this data be retained in a rugged folder or envelope. A sample format for a log sheet is provided in Appendix B. Photocopies of the log sheet should be made to allow you to make continued data entries. 1.5 Material Return Procedure To insure the efficient handling of equipment or components that have been returned for repair, ADC requests that each returned item be accompanied by a Material Return Authorization Number (MRA#). An MRA# can be obtained from any ADC Field Service Engineer by contacting the ADC Field Service Department, Broadcast Systems Division, at (724) 941-1500 or by fax at (724) 941-4603. This procedure applies to all items sent to the Field Service Department regardless of whether the item was originally manufactur…

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500-Watt VHF Transmitter Chapter 2, System Description 425A, Rev. 02-1 Chapter 2 System Description The 425A is a complete 500-watt VHF solid state internally diplexed television transmitter that operates at a nominal visual output power of 500 watts peak sync and an average aural output power of 50 watts, at an A/V ratio of 10 dB, 10% sound, or 25 watts at 13 dB, 5% sound. 2.1 System Overview The 425A (1064111) is made up of the trays and assemblies listed in Table 2-1. Table 2-1. 425A Major Trays and Assemblies MAJOR ASSEMBLY DESIGNATOR TRAY/ASSEMBLY NAMEDRAWING NUMBER A2AC distribution panel1265-1600 A4VHF exciter1070901 A6 and A7Two VHF amplifier trays1219-1100 A8VHF combiner assembly1219-1006 A9Bandpass filter assembly1067297 A12Remote interface assembly1083510 The (A4) VHF exciter can operate using either the baseband audio and video inputs alone or, if the (optional) 4.5-MHz composite input kit is purchased, the 4.5- MHz composite input or the baseband video and audio inputs to produce a diplexed, modulated, and on-channel frequency visual + aural RF output. The switching is accomplished by a relay on the sync tip clamp modulator board that uses a baseband select to control a relay that selects either the 4.5 MHz generated from the baseband inputs or from the 4.5-MHz composite input. To operate the transmitter with the (optional) 4.5-MHz composite input kit using baseband inputs, the baseband video must be connected to J1 or J2, the baseband audio must be connected to the proper input jack, and a baseband select must be connected from J7-6 and J7-7. To operate the transmitter with the (optional) 4.5-MHz composite input kit using the 4.5-MHz composite input, the 4.5-MHz composite input must be connected to J1 or J2 and the baseband select must be removed from J7-6 and J7-7. The RF output of the VHF exciter is split two ways in (A5) the 2-way power splitter assembly (ZFSC-2-2). The outputs of the splitter feed the two (A6 and A7) VHF amplifier trays that amplify the RF signals to approximately 300 watts each. The outputs of the two VHF amplifier trays are combined in (A8) the VHF combiner that provides approximately 600 watts peak of sync output. The 600-watt output is connected to (A9) a bandpass filter assembly. The bandpass filter is tuned to provide the high out-of-band rejection of unwanted products. The filtered signal is connected to A9-A5, a coupler assembly that provides a forward and a reflected power sample to the visual/aural metering board in the VHF exciter. The forward sample is processed to provide peak detected visual and aural power output samples to the transmitter control board in the VHF exciter. The reflected power sample is also peak detected and wired to the transmitter control board. The transmitter control board connects the visual, aural, and reflected power output samples to the front panel meter to monitor the system. 500-Watt VHF Transmitter Chapter 2, System Description 425A, Rev. 02-2 In the VHF amplifier tray, a forward power sample and a reflected power sample from the 4-way combiner board are connected to the dual peak detector board, single supply, that provides peak- detected forward samples to the amplifier control board that supplies the samples to the front panel meter of the tray. 2.2 Control and Status Control and status information for the transmitter is provided by the meter and LED indicators on the front panel of the VHF exciter. The switches and LED indicators are part of the (A17) transmitter control board that is mounted so that the switches and LEDs are operated or viewed from the front panel of the VHF exciter. Switch S1 is an Operate/Standby switch that controls the output of the transmitter by providing the Enables that, when the transmitter is in Operate, are needed to turn on the switching power supplies in the two VHF amplifier trays. In Operate, the green LED DS2 is on and in Standby the amber LED DS1 is on. If the transmitter does not switch to Operate when S1 is switched to Operate, check that a dummy jumper plug, with a jumper between pins 23 and 24, is connected to jack J11 on the back of the tray. The jumper plug must be connected to (A12-J9) when the (optional) remote interface panel is used. This jumper provides the interlock needed for the transmitter to operate. If the interlock is present, the green LED DS5 should be lit. Switch S2 is an Automatic/Manual switch that controls the operation of the transmitter by the presence of the video input signal. When the switch is in Automatic, the green LED DS3 is lit and, if the video input signal to the transmitter is lost, the transmitter will automatically switch to Standby. When the video input signal returns, the transmitter will automatically switch back to Operate. In Manual, the amber LED DS4 is lit and the operation of the transmitter is controlled by the front panel switches. During normal operation of the transmitter, switch S2 should be in the Auto position. The front panel of the VHF exciter also has LEDs that indicate a Video Fault (Loss; red LED DS9) and VSWR Cutback (amber LED DS7). 500-Watt VHF Transmitter Chapter 2, System Description 425A, Rev. 02-3 2.2.1 VHF Exciter Tray Table 2-2. VHF Exciter Tray Meters METERFUNCTION This meter reads power in terms of a percentage of the calibrated output power level on the upper scale. The voltage level or frequency level is read on one of the bottom two scales. A full-scale reading on the top scale is 120%. 100% is equivalent to the full-rated 500 watts peak of sync visual. The meter also reads % Aural Power, % Exciter Power, % Reflected Power, audio levels, video levels, and the ALC reading. With Switch S3 in Position Display Switch S3, Meter Selects the desired ALC voltage reading, % Exciter Power, % Reflected Power, % Visual Power, % Aural Power, video level, or audio level. Audio (0 to 100 kHz) Reads the audio level, ±25 kHz balanced or ±75 kH composite, on the 0 to 10 scale. Will indicate baseband audio, if it is co…

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500-Watt UHF Transmitter Chapter 3, Circuit Descriptions 425A, Rev. 03-1 Chapter 3 Circuit Descriptions 3.1 (A4) High-Band VHF Exciter (1070901; Appendix C) 3.1.1 (A4) Aural IF Synthesizer Board, 4.5 MHz (1265-1303; Appendix D) The aural IF synthesizer board amplifies each of the three possible audio inputs and the amplifier circuits that supply the single audio output. The balanced audio or the composite audio input is connected to the board while the subcarrier audio (SCA) input can be connected at the same time as either of the other two inputs. The board has the 4.5-MHz voltage-controlled oscillator (VCO) and the aural modulation circuitry that produces the modulated 4.5-MHz output. The board also contains a phase lock loop (PLL) circuit that maintains the precise 4.5-MHz separation between the aural (41.25 MHz) and the visual (45.75 MHz) IF frequencies. 3.1.1.1 Balanced Audio Input The first of the three possible baseband inputs to the board is a 600Ω-balanced audio input (+10 dBm) that enters through jack J2, pins 1 (+), 2 (GND), and 3 (-), and is buffered by U1B and U1C. Diodes CR1 to CR4 protect the input stages of U1B and U1C if an excessive signal level is present on the input leads of jack J2. The outputs of U1B and U1C are applied to differential amplifier U1A; U1A eliminates the common mode signals (hum) on its input leads. A pre-emphasis of 75 ms is provided by R11, C11, and R10 and can be eliminated by removing jumper W5 on J5. The signal is then applied to amplifier U1D whose gain is controlled by jumper W3 on J11. Jumper W3 on jack J11 is positioned according to the input level of the audio signal (0 or +10 dBm). If the input level is approximately 0 dBm, the mini-jumper should be in the high gain position between pins 1 and 2 of jack J11. If the input level is approximately +10 dBm, the mini-jumper should be in low gain position between pins 2 and 3 of jack J11. The balanced audio is then connected to buffer amplifier U2A whose input level is determined by the setting of balanced audio gain pot R13. The output of the amplifier stage is wired to the summing point at U2D, pin 13. 3.1.1.2 Composite Audio Input The second possible audio input to the board is the composite audio (stereo) input at BNC jacks J3 and J13. The two jacks are loop-through connected; as a result, the audio can be used in another application by connecting the unused jack and removing W4 from J12. Jumper W4 on jack J12 provides a 75Ω-input impedance when the jumper is between pins 1 and 2 of jack J12 and a high impedance when it is between pins 2 and 3. Diodes CR9 to CR12 protect the input stages of U6A and U6B if an excessive signal level is applied to the board. The outputs of U6A and U6B are applied to differential amplifier U2C, which eliminates common mode signals (hum) on its input leads. The composite input signal is then applied to amplifier U2B; the gain of this amplifier is controlled by composite audio gain pot R17. The composite audio signal is connected to the summing point at U2D, pin 13. 3.1.1.3 Subcarrier Audio Input The third possible input to the board is the SCA input at BNC jack J4. The SCA input has an input impedance of 75Ω that can be eliminated by removing jumper W2 from pins 1 and 2 of J14. The SCA input is bandpass filtered by C66, C14, R22, C15, C67, and R23 and is fed to buffer amplifier U3A. The amplified signal is then applied though SCA gain pot R24 to the summing point at pin 13 of U2D. 500-Watt UHF Transmitter Chapter 3, Circuit Descriptions 425A, Rev. 03-2 3.1.1.4 Audio Modulation of the VCO The balanced audio, or the composite audio and/or the SCA-buffered audio signals, are fed to the common junction of resistors R14, R20, and R27 that connect to pin 13 of amplifier U2D. The output audio signal at pin 14 of U2D is typically .8 Vpk-pk at a ±25-kHz deviation for balanced or .8 Vpk-pk at ±75-kHz deviation for composite as measured at TP1. This signal is applied to VCO U10. A sample of the deviation level is amplified, detected by U7A and U7B, and connected to J10 on the board. This audio-deviation level is connected to the front panel meter through the transmitter control board. The audio is connected to CR13 to CR16; these are varactor diodes that frequency modulate the audio signal onto the generated 4.5-MHz signal in U10. U10 is the 4.5-MHz VCO that generates the 4.5- MHz continuous wave (CW) signal. The output frequency of this signal is maintained and controlled by the correction voltage output of U5 PLL IC. The audio-modulated, 4.5-MHz signal is fed to amplifiers U11A and U11B. The output of U11B is connected to the 4.5- MHz output jacks at J7 and J8. 3.1.1.5 Phase Lock Loop (PLL) Circuit A sample of the signal from the 4.5-MHz aural VCO at the output of U11A is applied to PLL IC U5 at the F in connection. In U5, the signal is divided down to 50 kHz and is compared to a 50- kHz reference signal. The reference signal is a divided-down sample of the visual IF, 45.75-MHz signal that is applied to the oscillator-in connection on the PLL chip through jack J6 on the board. These two 50-kHz signals are compared in the IC and the fV, and fR is applied to the differential amplifier U3B. The output of U3B is fed back through CR17 to the 4.5-MHz VCO IC U10; this sets up a PLL circuit. The 4.5-MHz VCO will maintain the extremely accurate 4.5- MHz separation between the visual and aural IF signals; any change in frequency will be corrected by the AFC error voltage. PLL chip U5 also contains an internal lock detector that indicates the status of the PLL circuit. When U5 is in a "locked" state, pin 28 goes high and causes the green LED DS1 to illuminate. If the 4.5- MHz VCO and the 45.75-MHz oscillator become "unlocked," out of the capture range of the PLL circuit, pin 28 of U5 will go to a logic low and cause the red LED DS2 to light. A mute output signal from Q3 (unlock mute) will be applied to jack J9. This mute is connected to the transmitter control board. 3.1.1.6 Voltage …

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500-Watt VHF Transmitter Chapter 4, Installation and Setup Procedures 425A, Rev. 0 4-1 Chapter 4 Installation and Setup Procedures There are special considerations that need to be taken into account before the 425A can be installed. For example, if the installation is completed during cool weather, a heat-related problem may not surface for many months, suddenly appearing during the heat of summer. This section provides planning information for the installation and set up of the transmitter. 4.1 Site Considerations The transmitter requires an AC input line of 220 VAC with a rating of 20 amps for the exciter cabinet and 100 amps for each amplifier cabinet. Make sure that the proposed site for the transmitter has the necessary voltage requirements. The 425A is designed and built to provide long life with a minimum of maintenance. The environment in which it is placed is important and certain precautions must be taken. The three greatest dangers to the transmitter are heat, dirt, and moisture. Heat is usually the greatest problem, followed by dirt, and then moisture. Over-temperature can cause heat-related problems such as thermal runaway and component failure. Each amplifier tray in the transmitter contains a thermal interlock protection circuit that will shut down that tray until the temperature drops to an acceptable level. A suitable environment for the transmitter can enhance the overall performance and reliability of the transmitter and maximize revenues by minimizing down time. A properly designed facility will have an adequate supply of cool, clean air, free of airborne particulates of any kind, and no excessive humidity. An ideal environment will require temperature in the range of 40° F to 70° F throughout the year, reasonably low humidity, and a dust-free room. It should be noted that this is rarely if ever attainable in the real world. However, the closer the environment is to this design, the greater the operating capacity of the transmitter. The fans and blowers designed and built into the transmitter will remove the heat from within the trays, but additional means are required for removing this heat from the building. To achieve this, a few issues need to be resolved. The first step is to determine the amount of heat to be removed from the transmitter room. There are generally three sources of heat that must be considered. The first and most obvious is the heat from the transmitter itself. This can be determined by subtracting the average power to the antenna (350 watts) from the AC input power (3500 watts). This number in watts (3150) is then multiplied by 3.41, which gives 10,741, the BTUs to be removed every hour. 12,000 BTUs per hour equals one ton, so a 1-ton air conditioner will cool a 500-watt transmitter. The second source of heat is other equipment in the same room. This number is calculated in the same way as the equation for BTUs. The third source of heat is equally obvious but not as simple to calculate. This is the heat coming through the walls, roof, and windows on a hot summer day. Unless the underside is exposed, the floor is usually not a problem. Determining this number is usually best left up to a qualified HVAC technician. There are far too many variables to even estimate this number without reviewing the detailed drawings of the site that show all of the construction details. The sum of these three sources is the bulk of the heat that must be removed. There may be other sources of heat, such as personnel, and all should be taken into account. 500-Watt VHF Transmitter Chapter 4, Installation and Setup Procedures 425A, Rev. 0 4-2 Now that the amount of heat that must be removed is known, the next step is to determine how to accomplish this. The options are air conditioning, ventilation, or a combination of the two. Air conditioning is always the preferred method and is the only way to create anything close to an ideal environment. Ventilation will work quite well if the ambient air temperature is below 100° F, or about 38° C, and the humidity is kept at a reasonable level. In addition, the air stream must be adequately filtered to ensure that no airborne particulates of any kind will be carried into the transmitter. The combination of air conditioning for summer and ventilation during the cooler months is acceptable when the proper cooling cannot be obtained through the use of ventilation alone and using air conditioning throughout the year is not feasible. Caution: The use of air conditioning and ventilation simultaneously is not recommended. This can cause condensation in transmitters. For tube type transmitters, this can be especially serious if the condensation forms in the tube cavity and creates damaging arcs. The following precautions should be observed regarding air conditioning systems: 1. Air conditioners have an ARI nominal cooling capacity rating. In selecting an air conditioner, do not assume that this number can be equated to the requirements of the site. Make certain that the contractor uses the actual conditions that are to be maintained at the site in determining the size of the air conditioning unit. With the desired conditioned room temperature under 80° F, the unit must be derated, possibly by a substantial amount. 2. Do not have the air conditioner blowing directly onto the transmitter. Condensation may occur on, or worse in, the transmitter under certain conditions. 3. Do not isolate the front of the transmitter from the back with the thought of air conditioning only the front of the unit. Cooling air is drawn in at the front of all transmitters and in the front and back of others. Any attempt to isolate the front from the rear will adversely affect the flow of cooling air. 4. Interlocking the transmitter with the air conditioner is recommended to keep the transmitter from oper…

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