The Art of PCB Reverse Engineering: Unravelling the Beauty of the Original Design

365 Pages·2015·33.036 MB·English

by  Keng Tiong Ng

The Art of PCB
Reverse-Engineering

Ng Keng Tiong
Copyright © 2015 by Ng Keng Tiong. All rights reserved.
Cover designs (front and back) by the author.

Screenshots from Microsoft® Visio are used with permission from Microsoft. Both Microsoft and Visio
are registered trademarks of Microsoft Corporation in and outside the United States. Products and
service mentioned in this book are trademarks or registered trademarks of their respective companies.
All trademarks and registered trademarks in this book are the property of their respective holders.

No part of this book may be reproduced in any form, or stored in a database or retrieval system, or
transmitted or distributed in any form, by any means, electronic, mechanical, photocopying, recording,
or otherwise, without the prior written permission of the author.

LIMIT OF LIABILITY AND DISCLAIMER OF WARRANTY

The information, examples, illustrations, documentation, and other references in this book are
provided "as is", without warranty of any kind, expressed or implied, including without limitation any
warranty concerning the accuracy, adequacy, or completeness of the material or the results obtained
from using the material. Neither the publisher nor the author shall be responsible for any claims
attributable to errors, omissions, or other inaccuracies in the material in this book. In no event shall the
publisher or author be liable for direct, indirect, special, incidental, or consequential damages in
connection with, or arising out of, the construction, performance, or other use of the materials
contained herein.

Print copy ISBN-13: 978-1499323443
DEDICATION

This book is dedicated to all electronics enthusiasts
who share the same passion and appreciation for printed circuits
and possess the curiosity and tenacity of engineers
to unravel the beauty of the original design.

The Art of PCB Reverse Engineering 3
CONTENT

Acknowledgment 7

Preface 9

1 Before You Begin 17

What You Need to Know 18
Why Bother? 19
My Personal Story 20
Legal and Copyright Issues 25
The Three D's 27

2 Basic Preparation Work 31

Getting to Know Your PCB 31
Accessibility 32
Bill of Materials 33
Resistors and Networks 35
Capacitors 37
Inductors and Transformers 40
Fuses 42
Relays and Switches 43
Crystals and Oscillators 45
Diodes and Zeners 46
Transistors and MOSFETs 48
Integrated Circuits 49
Miscellaneous 54
Components without Markings 55
Missing Reference Designators 56
Filling up the BOM 58
Conformal Coating 60
Component Datasheets 62

The Art of PCB Reverse Engineering 4
Preface

3 Laying Out The PCB Artwork 67

Is it Really Necessary? 68
Getting to Know Microsoft Visio 69
Initial Visio Settings 70
Keyboard Shortcuts 76
Quick Maneuvering Tricks 76
Manipulating Objects 78
A Simple Example 80
Preparing the Drawing Page 81
Drawing the PCB Outline 86
Creating Component Layout Symbols 93
Populating the PCB 102
A Complex Example 106
More About Circuit Boards 108
PCB-Mount Fixtures 109
Bolts and Nuts 111
Connectors 112
Toggle Switches 115
Complex IC Layout Symbols 116
Drawing Analog Components 121
Mobbed! 127
Too Small to Ignore 130

4 Wiring Up The Schematics 135

Spaghetti, Anyone? 136
Basic Tools 136
ANSI or IEC? 141
Color or Monochrome? 142
Hierarchical or Flat? 144
Elements of a Good Schematic Diagram 145
Drawing Schematic Symbols 151
Approach and Strategy 175
It's an Analog World! 188
An ATX Power Supply Example 189
Strategy for Analog PCBs 192
One Useful Trick 197
A Word of Caution 198
Doing the Unthinkable 199

The Art of PCB Reverse Engineering 5
5 Advanced Topics 203
Layering Technique 203
Simplicity in Complexity 219
Generating Bill of Materials 257
The Matrix 263
Summary 270

6 Going From Here 273

Fabulous Freebies 274
Web-Based Wonders 277
Old–but not Obsolete 280
Commercial Suites 281
Rantings on Circuit Simulation 286
Summary 287

Appendix A Electronics References

Appendix B Visio References

Appendix C PCB Layout

Appendix D Schematic Entry

Appendix E Advanced Topics

Bibliographies

Index

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ACKNOWLEDGMENTS

This book would not have been possible without the understanding and support
of my wife, Bernice, when I expressed to her my desire to write a book of this
nature that is totally outside her knowledge domain.

Thanks to CreateSpace for making it easy for aspiring authors to publish and
distribute their works with its print-on-demand approach, removing all the
hassles and obstacles which would otherwise severely limit the availability or
prevented the circulation of this book.

The Art of PCB Reverse Engineering 7
8
PREFACE

I was introduced to Electronics at the age of 15 in my higher secondary school days. I was one of those
fortunate batches of students—in fact, the last in-take to study basic electricity and electronics in the
school's curriculum in 1978.

Electronics was totally new to me, and I had problem understanding some of the basic concepts back
then. It might surprise you that I had trouble figuring out the milli-, micro-, nano-, Kilo- and Mega-
prefixes in Ohm's Law, struggling with corrections and re-corrections in my class assignments I almost
gave up the subject for fear and frustration. Thankfully the light bulb turned on in me after a harrowing
first semester, and from then on there was no looking back as I went on to do well for my final exams
and did my major in Electronics and Communication for my tertiary education.

Due to family financial difficulties, I signed up with the Republic of Singapore Air Force (RSAF) after my
graduation as an aircraft radar and communications (RC) technician. I did well in the Air Engineering
Training Institute (AETI) and was selected for the E-2C Hawkeye program. In May of 1986, I attended a
six-month training at the Grumman Aerospace Corporation's premise in Long Island, New York. There
for the first time, I was introduced to the concept of automated test systems (ATS) as I learned how to
operate and maintain the CAT-IIID and RADCOM test stations, and used these awesome equipment to
perform test diagnostics on 75% of the E-2C's sophisticated avionics (radar, communications,
navigation, displays, power supplies, etc.)

My invaluable experience as one of the pioneers in setting up the E-2C squadron's third-line repair bay
and running the daily maintenance operation, as well as training three batches of local technicians,
laid a solid foundation for my engineering career in electronics, so much so that I was head-hunted and
invited to join Singapore Technologies (ST) Electronics Limited, a subsidiary of Singapore's home-grown
defense industry, ST Engineering Limited, right after my first contract with the RSAF expired. I've been
with the company since for over 23 years and now a Principal Engineer by title.

Learning is a life-long process. The same is true in electronics and in the field of test engineering,
which is still my primary job scope and interest. I've worked on a variety of printed circuit boards (PCBs)
from through-holes using the humble TTL logic circuits, to the high-density surface-mount type multi-
layered boards containing complex VLSI, FPGA and ASIC BGA chips. The rate at which integrated
circuits grow in complexity and density is staggering, especially in the last decade or so. Conventional
way of testing PCBs using in-circuit testers no longer seem practical or even feasible. Functional
approach has also become more challenging and is reaching a saturation point to be considered
viable. The way to go now would be boundary-scan (JTAG) testing for PCBs designed to take advantage
of this technology, though at the expense of chip and board real-estates, or hot-bed embedded testing
if design specifications are available for such implementation.

Ranting aside. The fact that you picked up this book inherently suggests that you have an interest (or
at least curiosity) in the topic of PCB reverse engineering. In this book, I will share what I've learned in
my years of working on PCBs with no schematic diagrams, my approach of assessing a PCB, analyzing
The Art of PCB Reverse Engineering 9
Preface
and reconstructing its electrical connectivity, the tools and methods I employed, useful tips to take
note, as well as pitfalls to avoid. Sprinkled in the footnotes you will find some interesting anecdotes
and personal takes to keep the subject of this book light-hearted and (hopefully) engaging.

WHAT THIS BOOK IS ABOUT

This book will not teach you to become proficient in using electronic design automation (EDA) tools or
software to produce or re-produce PCBs from schematic entry to gerber design files. It is not even
intended to give you a formal study on PCB structural design and fabrication. There are many books
out there that already addressed these topics and by authors who are certainly more knowledgeable
and the authority in these fields.

That said, this book does impart knowledge on PCBs that relate to the subject of reverse engineering,
as a basic understanding of any PCB you intend to reverse engineer is essential to your success. Also, I
will be using Microsoft® Visio albeit in a generic manner to demonstrate the steps involved. I said
'generic' because I'm not advocating any particular version or release of this diagramming tool, which
was originally sold and distributed by Shapeware in 1992 (subsequently called Visio Corporation in
1995 when it went public listed), but was acquired by Microsoft Corporation in 2000.

HOW TO USE THIS BOOK

This book is written for easy reading. While you may choose to read selectively since each chapter is a
self-contained unit, you are encouraged to go through the book sequentially to derive the maximum
benefit. I suggest you read Chapter 1 before launching out to explore the other chapters. A summary of
the chapters are listed below:

▪ Chapter 1 I know you're eager to get started right away, but it's good to know a little of what
you're getting into before you plunge in completely. You'll need to have certain background in
electronics. I'll mention some available alternatives to doing reverse engineering completely by
hand, though they're not necessarily affordable unless you have deep pockets and are willing
to part with your hard-earned cash. I'll also share my personal story on what started me on this
journey (hopefully a good and inspiring read to you). Then there's the copyright issue which I'll
give my personal take on it, before rounding up the chapter with a little work philosophy.

▪ Chapter 2 This chapter may be thought of as a practical introduction or revision to electronics
in terms of the various building blocks of a PCB—resistors, capacitors, inductors, fuses, relays,
diodes, zeners, transistors, MOSFETs, and ICs, etc. You may think it's boring or too elementary
but I've put in quite a substantial amount of information here, so you should be able to find
some rare gems among the junks (to borrow a phrase from the PCB recycle industry). I'll deal
with components without markings and reference designators, touch on a bit about conformal
coatings, as well as how component datasheets will be a great help later on. These elements
formed what I call the ABCD's of preparation work—an essential step that will save you a lot of
time and trouble when you start to do the real work.

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