TEE [VISION BROADOASTINO Camera Chains by Harold E. Ennes r II pRO 1 II II U18700 3828588 A Television Broadcasting Camera Chains by Harold E. Fennes HOWARD W. SAMS & CO., INC. THE BOBBS -MERRILL CO., INC. INDIANAPOLIS KANSAS CITY NEW YORK FIRST EDITION FIRST PRINTING -1971 Copyright © 1971 by Howard W. Sams & Co., Inc., Indianapolis, Indiana 46206. Printed in the United States of America. All rights reserved. Reproduction or use, without express permis- sion, of editorial or pictorial content, in any manner, is prohibited. No patent liability is assumed with respect to the use of the infor- mation contained herein. International Standard Book Number: 0- 672 -20833 -4 Library of Congress Catalog Card Number: 71- 157802 Preface The manufacturers of television camera chains normally provide instruc- tion manuals that range from preliminary (sketchy) data to elaborate coverage of circuit theory, operations, and maintenance of the specific equipment. Such manuals obviously cannot delve into certain training programs that are usually necessary before adequate comprehension of modern broadcast technology can be gained. It is the purpose of this book to provide the fundamental and advanced training that is necessary if full benefit is to be obtained from the infor- mation in modern instruction books. To do this most effectively, where possible, complete, detailed schematics have been avoided, and, instead, use has been made of block diagrams with simplified diagrams of indi- vidual blocks under discussion. The overall system concept is stressed so that the reader can more readily grasp the meaning of a specific circuit adjustment in terms of its effect on system performance. For the serious student, or for the practicing engineer, the information contained in the author's previous two books should be considered pre - requisities to a study of this volume. These books are Workshop in Solid State and Television Broadcasting: Equipment, Systems, and Operating Fundamentals. Both are published by Howard W. Sams & Co., Inc. These books and the present volume serve a dual purpose, as basic textbooks for students or beginners and as factual guidebooks for practicing technicians. The author extends his appreciation to the following organizations for providing information and photographs used in this book: Albion Optical Co.; Ampex Corporation; Amphenol Corporation; Belden Corporation; Cohu Electronics, Inc.; Hewlett- Packard Co.; International Video Corpor- ation; Kliegl Bros. Lighting; Philips Broadcast Equipment Corp.; RCA; Shibaden Corp. of America; Tektronix, Inc.; TeleMation, Inc.; Telesync Corp.; Visual Electronics Corporation; WBBM-TV; and WTAE -TV. HAROLD E. ENNES f Contents CHAPTER 1 STUDIO LIGHTING 11 1 -1. Amount of Light 11 1 -2. Air Conditioning 23 1 -3. Power Requirements for Lighting 24 1 -4. The Suspension System and Power Distribution 25 1 -5. Lighting Control 26 CHAPTER 2 THE SYSTEM CONCEPT 36 2 -1. NTSC and FCC Color Standards in Practical Form 36 2 -2. Evolution of the Color -Bar Signal 55 2 -3. Defining and Recognizing "Distortions" in NTSC Color 57 2 -4. Digital Concepts 72 2 -5. A Digitally Controlled Color Camera 81 CHAPTER 3 CAMERA MOUNTING, INTERCONNECTION FACILITIES, AND POWER SUPPLIES 90 3 -1. The Camera Pan and Tilt Cradle 90 3 -2. Pedestal Dollies 93 3 -3. The Crane Dolly 96 3 -4. Prompting Equipment 97 3 -5. Camera -Chain Power Supplies 99 3 -6. Camera -Chain Power Distribution 107 3 -7. Power -Supply Maintenance 112 3 -8. Interconnecting Facilities 123 CONTENTS CHAPTER 4 THE CAMERA PICKUP TUBE, YOKE ASSEMBLY, AND OPTICS 134 4 -1. The Image Orthicon 134 4 -2. The Yoke Assembly 152 4 -3. Yoke Maintenance 157 4 -4. Special Notes on the 3 -Inch Field -Mesh I.O. 159 4 -5. The Image-Orthicon Cooling System 161 4 -6. The Vidicon 162 4 -7. The Lead -Oxide Vidicon 180 4 -8. Camera Optics 182 4 -9. The Iris -Control Servo 190 CHAPTER 5 VIDEO PREAMPLIFIERS 193 5 -1. The Vacuum -Tube Video Preamplifier 193 5 -2. Solid -State Video Preamplifiers 198 5 -3. Maintenance of Video Preamplifiers 205 CHAPTER 6 VIDEO PROCESSING 222 6 -1. The True Meaning of Bandwidth 222 6 -2. The Television -Camera Resolution Chart 233 6 -3. Clamping Circuitry 236 6 -4. Aperture -Correction Circuitry 244 6 -5. Cable Equalization 251 6 -6. Gamma Correction 251 6 -7. Blanking and Sync Insertion 258 6 -8. Testing and Maintenance 260 CHAPTER 7 PULSE PROCESSING AND TIMING SYSTEMS 271 7 -1. The Automatic Timing Technique 271 7 -2. Level-Control Pulses (Manual and Automatic) 279 7 -3. Level Calibration and Test Pulses 284 7 -4. Camera Deflection Circuitry 292 7 -5. Pickup-Tube Protection 299 7 -6. Shading -Signal Formation 303 CONTENTS CHAPTER 8 CAMERA CONTROL AND SETUP CIRCUITRY 308 8 -1. The RCA TK -60 Monochrome Camera Chain 308 8 -2. The Marconi Mark VII Four-Plumbicon Color Camera 315 8 -3. The RCA TK -44A Camera Control 321 8 -4. The Camera Waveform Monitor 327 8 -5. Camera Interphone 333 CHAPTER 9 THE SUBCARRIER AND ENCODING SYSTEM 337 9 -1. The Dot Structure in NTSC Color 337 9 -2. Power -Line Crawl on Color Standards 339 9 -3. Adjusting the Subcarrier Countdown 340 9 -4. Solid -State Counters 345 9 -5. Final Subcarrier Generator Countdown Check 348 9 -6. Final Check on Sync- Generator Color Lock 349 9 -7. Setting the Color -Subcarrier Frequency 349 9 -8. The Color -Sync Timing System 350 9 -9. Adjustment of Burst -Key Generator With Encoded Signal .. 354 9 -10. Adjustment of Burst -Key Generator by Itself 356 9 -11. The Encoding Process 358 9 -12. The Vectorscope 379 CHAPTER 10 COLOR PICTURE MONITORING SYSTEMS 394 10 -1. Analysis of Basic I -and -Q Decoder 394 10 -2. Color Picture -Tube Circuitry 413 10 -3. Adjustment of Color Monitors 418 10 -4. The RCA TM -21 Color Monitor 423 10 -5. The X and Z Demodulator 432 10-6. Use of the Color Monitor in Matching Techniques 434 CHAPTER 11 PREVENTIVE MAINTENANCE 437 11 -1. The Vidicon Film Chain 437 11 -2. General Preventive Maintenance 442 11 -3. Troubleshooting 445 CONTENTS APPENDIX ANSWERS TO EXERCISES k 15 INDEX -i6 1 CHAPTER 1 Studio Lighting The television camera depends primarily on the reflected light it "sees" through the optical system. Optimum performance is possible in the studio, where light can be controlled to shape the "taking" characteristics. In an "adequate" studio lighting system, we are concerned with the following basic factors: 1. Amount of light, and color temperature 2. Flexibility 3. Light control It is assumed that the reader has basic knowledge of the types and tech- niques of lighting.' 1 -1. AMOUNT OF LIGHT It is possible to relate foot -candles (fc) to watts, lumens, etc., but such a study, while interesting from an academic viewpoint, is of little value to the practicing operator. Information regarding the amount of light at a given distance and direction from a given source is furnished by manu- facturers of lighting equipment. Any conversion of watts to foot- candles to lumens is useless unless the particular angle of throw, type of lamp, and type of reflector are accounted for. The number of lighting fixtures may vary from 20 to 25 in a small limited -program studio to more than 200 in a larger multiple -purpose studio. The amount of light required depends on the size and purpose of the studio, whether programs are in monochrome or color, and the de- gree of flexibility required. The key word for good studio lighting sys- tems is flexibility. 'See, for example, Harold E. Ennes, Television Broadcasting: Equipment, Systems, and Operating Fundamentals (Indianapolis: Howard W. Sams & Co., Inc., 1971). 11 12 TELEVISION BROADCASTING CAMERA CHAINS From previous experience, the foundation for an adequate amount of light can be laid as in Table 1 -1. The higher values are representative of more complex productions, such as large variety shows with liberal use of effects and modeling lighting both foreground and background. Note in connection with this table that the quartz lamp has more light output per watt of input power over a broader area than the incandescent lamp has. Also, the size and shape of the quartz lamp permits design of reflectors of higher efficiency. The net production area to which Table 1 -1 applies is the actual area used within the cyclorama curtain. The net production area can be approxi- mated by subtracting an area 4 feet wide all around the perimeter of the studio. For instance, a 40' X 60' studio (2400 square feet) has a net pro- duction area of 32' X 52', or 1664 square feet. However, smaller studios, such as the one in the following example (20' X 30') , do not always em- ploy cycloramas, and the wall -to -wall dimensions normally are used for these studios. Table 1 -1. Light Requirements for Net Production Area 100% Incandescent 100% Quartz Monochrome 25 -35 W /ft2 10 -20 W /ft2 100 -125 fc (Nominal: 30 W /ft2) (Nominal: 15 W /ft2) Color 75-110 W /ft2 40-60 W /ft2 250 -350 fc (Nominal: 90 W/ft2) (Nominal: 50 W /ft2) A typical incandescent lighting package for a 20' X 30' studio with a 15 -foot ceiling is illustrated in Fig. 1 -1. On the basis of the nominal values shown for incandescent lights in Table 1 -1, this 600- square -foot studio would require a total of 18,000 watts for monochrome, or 54,000 watts for color. Note from the equipment list in Fig. 1 -1 that two wattages are listed for each fixture. In most instances, the lower- wattage lamps would be used for monochrome, and the higher- wattage lamps would be used for color.