Newnes Television and Video Engineer's Pocket Book Third Edition

Newnes Television and Video Engineer’s Pocket Book ThisPageIntentionallyLeftBlank Newnes Television and Video Engineer’s Pocket Book Third edition Eugene Trundle, TMIIE (elect), MRTS, MISTC OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI Newnes An imprint of Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801–2041 A division of Reed Educational and Professional Publishing Ltd A member of the Reed Elsevier plc group First published 1987 Reprinted 1987 Second edition 1992 Reprinted 1994, 1995, 1996, 1997 Third edition 1999 © Eugene Trundle 1999 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 9HE. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN 0 7506 4194 0 Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress. Typeset by The Midlands Book Typesetting Company, Loughborough Printed by Antony Rowe Ltd, Chippenham, Wilts CONTENTS Preface 1 Components and assemblies 1 2 TV and video waveforms and standards 9 3 Aerials and receivers 44 4 Satellite television 62 5 Image display and capture devices 99 6 TV cameras and analogue colour encoding 128 7 TV signal processing 151 8 Teletext reception 170 9 Nicam stereo sound 180 10 Timebase circuits 196 11 Power supply systems 219 12 Digital TV 242 13 Video on magnetic tape 263 14 Videorecorder signal processing 283 15 Servo systems 308 16 Videorecorder deck control 324 17 Audio record and playback 344 18 Tape deck mechanics and servicing 360 19 Digital camcorders and VCRs 379 20 Video disc technology 393 21 Surround-sound and home cinema 412 22 Control systems 424 23 Test equipment and fault diagnosis 445 24 Reference data 473 Index 493 PREFACE The purpose of this book is to present a reasonably full picture of the systems, formats and technology of contemporary TV and video equipment, along with reference data, primarily for the practising service engineer. There has been tremendous diversification of home entertainment and educational products; embodied in them are techniques and artifices drawn from all branches of electronics as well as high-precision optics and mechanics. Like the equipment it describes, the book encompasses a mixture of analogue and digital systems, and several chapters are wholly given over to digital topics, reflecting the trend in consumer equipment. The colour picture-tube is the main ‘analogue’ component in current TV equipment, and its peripheral circuits and components are neces- sarily analogue in nature; indeed they account for most breakdowns. My thanks are due, as on many past occasions, to those broadcast- ers and equipment manufacturers who helped me with diagrams and data. Again my wife Anne gave me invaluable moral support and expertly keyed in the manuscript, while my son Paul helped with the diagrams. As a full-time service engineer, I can strongly identify with the read- ers of this book. Few people appreciate what is involved in fault diagnosis and servicing of home electronic equipment, or the strug- gles and problems involved – not all of which arise from the equipment itself! The book, then, is dedicated to service engineers everywhere, who are daily expected to competently deal with lasers and LOPTs, microvolts and kilovolts, data buses and dirty switch contacts, camcorders and computers. Eugene Trundle CHAPTER 1 COMPONENTS AND ASSEMBLIES All electronic equipment uses components, passive (R, C, L and some diodes) and active (transistors, ICs etc.), built up into assemblies to make complete operational units; some units, like the videorecorders and disc players examined later in this book, have mechanical assemblies as well. This section surveys the most common building blocks in electronic systems. Type-coding and formulae are given in Chapter 24. RESISTORS The basic function of a resistor is to impede the passage of an electrical current, absorbing energy and dissipating it as heat. The vast majority of resistors in use dissipate less than 500 mW, and the most common are metal-oxide and metal-film types, which (due to their superior accuracy and stability) have superseded carbon composi- tion types. Metal-film resistors have low inherent noise and high stability, and are available in a wide range of values and sizes. Metal- oxide types have better power-dissipation capabilities, and are generally based on the resistive properties of stannic oxide, SnO2. Wire-wound resistors are used for higher-dissipation applications, from about 2 W upwards – as equipment becomes more efficient, high-power resistors are being ousted, along with the unwelcome heat they generate. Wire-wound resistors can be made to close tolerances and high accuracy, and thus find ‘precision’ applications – in test equipment, for instance. Other types of resistor are: metal glaze, whose characteristics are high resistance in small sizes, and resistance to external heating; Cermet, with similar virtues; and thick-film, made by screen-printing a carbon- loaded ink onto a substrate, and, typically in the form of ‘packages’, incorporating several resistors for non-critical applications. There is a wide range of non-linear resistors for special applications. Amongst the most common types are VDR (Voltage Depend- ent Resistors), whose value depends on applied voltage, and thermistors, whose resistance varies with temperature. They are usually made of manganese oxide or nickel oxide, giving the thermistor a negative (falling resistance) reaction to heat, either externally sup- plied or generated internally by the passage of current. 1 Variable resistors have some form of conductive wiper which can be set to any point on the resistive track, and in domestic equipment these range from large double-gang volume controls to tiny PCB- mounted presets. Their tracks are carbon-coated or carbon-suffused, and may have a linear, logarithmic (volume controls) or other relationship to the physical position of the slider. In many cases variable resistors are being superseded by ‘software-control’ from microprocessor ICs. Fixed resistors are available in various logarithmic series of standardised values, designated E12, E24, E96 etc., the number indicating how many different values are available in each decade. The standard range is E24: 1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1 and their decades. CAPACITORS A capacitor consists basically of two conductive plates separated by an insulator (dielectric). It has the ability to store a charge of electric- ity, proportional to its capacitance, which for general use may range from 1 pF to 10 000 μF, and may be more for special applications like clock back-up stores in videorecorders. Capacitors are broadly divided into two classes, non-polarised and electrolytic. The first category has a dielectric typically of ceramic or plastic- film material. Ceramic capacitors are formed by evaporating metal electrodes onto a ceramic insulator, and can take many physical forms: tube, disc, plate and multilayer. With different ceramic types, characteristics like temperature coefficient, physical volume and capacitance can be traded off. Plastic-film capacitors are generally larger than ceramic types for the same electrical ratings; they have metal-foil or metal-film electrodes and dielectrics of polyester, polystyrene, polypropylene or polycarbonate. With their relatively large physical volume and dislike of high body temperatures during soldering, film capacitors do not lend themselves to modern PCB techniques as well as ceramic types. Electrolytic capacitors have the highest capacitance per unit size, and are generally used in values above 0.1 μF. They depend for their operation on a very thin oxide film formed on the surface of the posi- tive plate by electrolysis when a d.c. polarising voltage is applied. There are two basic types of electrolytic capacitor: aluminium and tantalum. Aluminium types are available in higher capacitance ranges than tantalum, and are commonly used as PSU reservoirs and for smoothing and decoupling on supply lines. Tantalum capacitors are 2 marginally less reliable, but have a size advantage (smaller) and higher permissible operating temperature. Variable capacitors are now rare, except in varicap diode form, described below. INDUCTORS Inductance concerns the magnetic properties of a current-carrying conductor; all conductors are surrounded by magnetic fields. Practi- cal inductors concentrate the magnetic field by winding the conductor into a coil with (usually) a magnetic core of ferrite or laminated iron. A basic property of an inductor is its ability to turn electrical energy into magnetic energy and vice versa. Examples are solenoids, relays, recording heads and loudspeakers in the one case, and replay heads, ferrite-rod aerials, phono pick-ups and VCR-motor PG/FG generators in the other. Transformers convert an alternating current into a strong, ‘tight’ magnetic field which induces a current in the secondary winding, usually at a different voltage: transformation ratio is proportional to wire-turns ratio. The size of an inductor, for practical purposes, is generally proportional to the current it carries, and inversely proportional to the frequency at which it works. In conjunction with capacitors, inductors can form resonant circuits, the formulae for which are given in Chapter 24.

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