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THE PROFESSIONAL MAGAZINE FOR ELECTRONICS AND COMjUTER SERVICING

G1E01'11011'0Servicing & Technology February 1995/S3.00

New technology update

Some general software packages

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Contents

page 13

FEATURES6 General software for the

service centerBy The ES&T StaffMost businesses have at least onecomputer to handle customer infor-mation, inventory, accounting, andmore. This article looks at othertypes of software that can be usefulin the service business.

10 New technology updateBy The ES&T StaffConsumer electronics servicingtechnicians can always count on theimprovement of consumer elec-tronics products. Here are sometechnological innovations that read-ers might be interested in.

13 Ten steps to successful servicingBy Brian PhelpsIf the service technician follows theten steps recommended by authorBrian Phelps, they will undoubted-ly lead him to successful servicing.

16 VCR service centers: Some tipson remaining profitableBy Wayne B. GrahamBy following some of these VCRservicing tips, your center mayremain profitable.

THE PROFESNONAL MAGAZINE FOR ELECTRONICS AND COMPUTER SERVICING

ELECTRONICServicing & Technology

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page 4242

20 Magnetic recording principlesBy Lamar RitchieAn article in the January issuedescribed the principles of magnet-ic recording, and provided specificdetails on audio recording. This arti-cle looks at the recording of video,with detail on VHS, Beta and 8 -mm.

26 Coping with hard diskproblems-Part IIBy Stephen J. BigelowPart two of this three-part articlelists some of the hard drive hard-ware error messages that a techni-cian may encounter and suggests acourse of action to take when theyare encountered.

42 Electronic tuner theory andtroubleshooting-Part IBy Steve BabbertThis two-part article tries to demys-tify the electronic tuner and outlinesome basic troubleshooting proce-dures. Part one looks at theory.

50 Troubleshooting secondaryvoltage circuitsBy Homer DavidsonDetermining the cause of chassisshutdown, overloaded power sup-ply circuits or isolating defectivecomponents in the secondary cir-cuits of the horizontal output trans-former can consume a great deal ofservicing time. Here are some tips.

Volume 15, No. 2 February 1995

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DEPARTMENTS -2 Editorial

4 News

9 Products

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19 Test Your Electronics KnowledgeTerms defined

31 Profax

57 Photofacts

58 Computer CornerNetworking basics

60 What Do You Know AboutElectronics?Working with fractions

62 Books

63 Literature

64 ES&T Calendar of Events

65 Classifieds/Readers' Exchange

67 Advertisers' Index

ON THE COVERIt is a lot tougher these days for servicecenters to make money servicing VCRs.Many service centers may not survivethe transition caused by the low-pricednew units available on the market. Thereare some things a service center can doto increase the likelihood of survival.(Photo courtesy of Tentel)

February 1995 Electronic Servicing & Technolcgy 1

Editorial

Computersandsoftware

When the first computer was built, ithad a very limited and specific purpose:to calculate the trajectories of artilleryprojectiles to be fired during World WarII. By today's standards, it really wasn'tmuch of a computer. Even though it washuge, and took kilowatts of electricity tooperate it, it had limited computingpower, and was programmed by the pathsof wires in a wiring patch panel.

Since those early days, computers haveevolved from vacuum tubes to transistors,then to integrated circuits, and haveshrunk in size from something that wouldfill several rooms to something that willfit into a shoe box.

Every bit as important as the evolutionof the hardware is the evolution of thesoftware. In those early days, and formany years since, the user of any com-puter had to pretty much program it forhimself, or hire someone to program it.As with any technology, that meant thatonly people who were computer profes-sionals were using computers, or peoplewho could afford to hire a computer pro-fessional to program their computers.

Over the years, computer software hasbeen written to be easier to use, and soft-ware manufacturing companies havechurned out huge numbers of softwareprograms that cover a broad range ofinterests that are extremely comprehen-sive, and that are easier and easier to use.

The first general-purpose softwarepackage that really caught on with per-sonal computer users was the wordprocessor. Early versions of this softwarewere really a huge improvement over thevenerable typewriter. The most obviousadvance was that now a writer or typistcould type a document into the comput-er, check it over, make corrections on thescreen, rearrange words, sentences, andparagraphs, and turn out a perfect docu-ment without doing any major retyping.

Over the relatively few years duringwhich word processing software has exist-ed it has undergone major improvements.In those early days, a word processor couldturn out a pretty good looking letter. Today,a word processor with page layout capa-bilities can turn out a letter, a newsletter,or even a camera-ready magazine page,complete with photos and line art.

Other software has undergone similarevolution. Spread sheet and database

software have evolved from relativelysimple programs that could crunch num-bers or store and retrieve data to full -fea-tured programs that include word pro-cessing and graphic capability. Specificapplication software based on databaseprograms, such as contact managementsoftware, allow someone who has only arudimentary knowledge of computers touse all of the power that a computer offers.

Specific applications software has evenmade computer users and enthusiasts ofpeople who really weren't interested incomputers in the abstract. For example, Iknow one man, Jack, who got involved incomputers because of his love of flying.

I met Jack at an electronics associationconvention. He was selling an on-linetroubleshooting tips database service. Hewas not a computer professional or anelectronics professional, so I asked himhow he came to be involved with both.

Jack's reply was that he loves to fly, butcan't do so as often as he'd like, so whenhe became aware of a personal computerbased flight simulation program, hebought a computer and a copy of the pro-gram. He then became a computer enthu-siast and that led to his employment withthe database service company.

Because they're such general-purposeinformation-processing machines, andbecause they have become so much easi-er to use, computers are being used by peo-ple who have no interest in "computers"as such. Artists paint and draw using thecomputer. Graphic designers lay out news-paper and magazine pages using the com-puter. Sales people manage their lists ofcustomers and contacts using computers.In their homes, people store and retrieverecipes, keep inventories, design and pro-duce cards and banners using computers.

The computer has also been a boon toconsumer electronics service. Not onlydo service centers use computers to helpmanage the business and to store andretrieve troubleshooting information, butthey are also products that service centerscan make a profit on servicing. And as thecontinuing evolution of software makescomputers more general in purpose andeasier to use, more consumers will havecomputers that need to be serviced.

2 Electronic Servicing & Technology February 1995

SMARTMANIS HERE!Free yourself from the stacks of paper serviceliterature that keep your shop from reaching its fullpotential! SmartMan is the "engine" component ofa powerful servicing machine. It allows completeinteraction with other Philips Technical Trainingprograms -it accesses Parts Pricing, SmarTips,and PartSeeker. Plus, you can get informationin three different forms for yourconvenience-SmartFiche, SmartBasic,and SmartManual.

Order your SmartMan program today,and work faster, be more productive,and generate more profit with softwarefrom Philips Technical Training!

Other Software Available:Parts Pricing and Cross -Reference Program(Version 2.0)With over 260,000 part numbers cross-referenced from Philipsnumbers to generic and back, this program is ideal for keepingyour old parts inventory under control. It also includes all VCRgeneric part numbers found in our sets (as well as many othergeneric numbers) and lists pricing, Dud allowance, de!cription,availability, and subs for each number. And, you can use it inconjunction with PartSeeker to access service manual parts!

PartSeekerFind any part number found in any of our TV and PTV modelsor chassis (over 12") since 1985! Whether through scanning orby direct input (27C8), you'll immediately see model parts on thescreen, and chassis numbers will be just one key away. Type R14to find a part number. Hit F2 to see the price, subs., andavailability for that number (you must already have the PartsPricing and Cross -Reference Program). And, this program can beupgraded to include VCR, camcorder, CD, etc. Subscriptions areavailable for continued growth and accuracy.

SmarTipsLocate Philips Service Tips on Ns, tuners, VCRs, camcorders,CD -audio and video players, monitors, etc. right in yoircomputer! Just a few keystrokes, and you have a list of tips on

Philips, Magnavox, Sylvcnia, and Philco products tc help solvesome of the difficult repcirs encountered every day. Tips aretaken from Service Reporters and from reports called in tc ourTechnical Assistance Department-you can even add your owntips to the list!

Update #1 and #2 foromson's FixFinder Program

If you have Thomson's Fixfinder Program, and you servicePhilips, Magnavox, Sylvcnia, or Philco TVs, VCRs, andcamcorders, you siouldr't be without these updates! Tips 'tomService Reporters, Service Bulletins, and from reports called into ou- Technical Assistance Department are incorpo-ated intothe program to make servicing easier.

VCR Cross -ReferenceKeep your parts irventory under control! Get rid of old stock!This easy -to -use program lists 31 different manufacturers' VCRsby model number. You can access any one of them by modelnumber, manufacturer, o- part number. It even includes pr cingand Dud allowances for parts.

PH LIPS Cal today, and discoverTEcHithe convenience ofinteractive serviceliterature!software

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NewsCalifornia State Electronics

Association becomes ProfessionalServicers Organization of California

The California State Electronics Asso-ciation became known as the ProfessionalServicers Organization of Californiaeffective January 1, 1995. After a com-plete reorganization that took almostthree years to accomplish, the membersvoted in the new name at a meeting heldon November 11 to 13, 1994.

The new system will allow the unifica-tion of all industries that are in service andfinally be the voice for all. It intends towork together with all to provide a betterfuture for the organization, its membersand the service industry.

Video sales set new standardsfor October

The video market continued to set newsales standards in October 1994. Ac-cording to the Electronic IndustriesAssociation, all-time October bests wererecorded for direct view color TVs, pro-jection TVs, camcorders, and TVNCRcombinations.

"Despite consumer uncertainty aboutthe future of the economy, we're stillexperiencing considerable growth in thevideo market," stated Jack Osborn, pres-ident and chief operating officer ofMitsubishi Consumer ElectronicsAmerica, Inc. "Our research indicatesthat there is a significant amount ofreplacement buying underway and thehome rebuilding cycle is finally begin-ning to affect television sales. Addi-tion-ally, consumers have plenty of disposableincome and manufacturers have intro-duced aggressive credit promotions toprovide incentives for other groups ofconsumers.

Combined sales of all video productswere up 10 percent over October 1993,and are up 8 percent for the year to date.Video sales are benefitting from a strongdomestic economy (3.5 percent growth inthe third quarter), although consumerpurchases of these products are in starkcontrast to their perceptions on the econ-omy as a whole. In a recent poll of 708adult consumers conducted by theBloomberg Business Report, 59 percentbelieve the U.S. economy is still in arecession. Another study of 1,000 adultsby ABC News reported only 32 percent

of those surveyed feel the economy isimproving. But that broad pessimismabout the economy hasn't dampened buy-ing expectation for video products.Buying intentions for color TVs, VCRdecks, and camcorders were up fraction-ally in October from the previous month.

Color TV sales rose a solid 6 percent inOctober and are up 8 percent for the yearto date. Shipments of 25 -inch sets wereparticularly strong rising 13 percent inOctober. Additionally, projection TVswere up 40 percent in October, helpingthe projection market to average month-ly growth of 39 percent through the first10 months of 1994. It has had only onemonth where growth was less than 21 per-cent (14 percent in January 1994).

Sales of VCR decks set an all-timeOctober high with volume of over 1.5 mil-lion units (up 16 percent over 1993).Monaural decks outperformed stereomodels by a small margin. Additionally,camcorder sales were up 4 percent in themonth and are up an additional 4 percentin the year to date.

Osborn says that when all the 1994numbers are in, "I believe we'll see recordsales." Clearly the growth is in the hometheater market and large screen TVs arethe driving force for the video market. Butother video categories are showingstrength as well, and should remainhealthy well into 1995. Camcorder salesare up, and VCR decks continue to be astrong seller in the market. In the end,consumers will benefit tremendouslyfrom the vitality of this segment of themarket. It all comes down to a few basicconcepts for our industry; value, quality,and the availability of cash by the con-sumers or reasonable credit terms. Whenthey've got the cash, they want to buysomething that lasts, and that means ourproducts," concluded Osborn.

EIA is the 70 -year -old Washington,D.C.-based trade association represent-ing all facets of electronic manufacturing.EIA's Consumer Electronics Group rep-resents U.S. manufacturers of audio,video, home office, home automation,mobile electronics, and accessories prod-ucts, as well as assistive devices for peo-ple with disabilities.

Mobile Electronics Show targetssuccess in Philadelphia

The 1995 Mobile Electronics Show

(MES), the "Spring Break '95" event forthe 12 -volt industry will be rolling intoPhiladelphia's Pennsylvania ConventionCenter April 7 through April 9, 1995.Each year the success of MES reflects thegrowing interest of consumers in pur-chasing mobile electronics products.Products featured at MES include auto -sound and security, as well as pagers, cel-lular, vehicle navigation products andmobile electronics accessories.

MES has signed more than 83 ex-hibitors and allocated more than 57,000square feet of exhibit space.

"Considering that we have already soldmore than half of last year's total exhibitspace and we are six months out from theShow, we expect a very successfulturnout in 1995," said Robbi Lycett, MESshow manager. "Our goal is to exceed lastyear's record show in terms of size. Weexpect to sell out the show after the WinterCES in January."

Lycett added that exhibitors are excit-ed about the new Philadelphia location forthe show which has taken place in Atlantain 1993 and 1994. In 1994 the ElectronicIndustries Association (EIA) co -spon-sored the MES with Bobit Publishing, theShow founder. EIA assumed the role ofsole manager of MES beginning with the1995 Show. All profits from the Show arereinvested into the programs and activi-ties of the EIA, including the MobileElectronics Certification Program(MECP) and other services for the mobileelectronics industry which are offered byEIA/CEG's Mobile Electronics Division.

Mobile Electronics, otherwise referredto as the 12 -volt industry, is one of thefastest growing segments of the consumerelectronics industry. According to theElectronic Industries Association, themobile electronics industry-includingaftermarket autosound, cellular tele-phones, pagers and aftermarket vehiclesecurity-will grow an estimated ninepercent in 1994, and five percent in 1995.

The 1996 Mobile Electronics Showwill take place in Orlando, April 19through 21, 1996.

EDS offers traveland housing discounts

The Electronic Distribution Show andConference (EDS) has made it even eas-ier to travel to Las Vegas for EDS '95.EDS has negotiated a number of travel

(Continued on page 64)


THE PROFESSIONAL MAGAZINE FOR ELECTRONICS AND COMPUTER SERVICING

ELE0111111110Servicing & TechnologyElectronic Servicing & Technology is edited for ser-vicing professionals who service consumer electronicsequipment. This includes service technicians, field ser-

vice personnel and avid servicing enthusiasts who repair

and maintain audio, video, computer and other con-sumer electronics equipment.

EDITORIALNils Conrad Persson, EditorLinda Romanello, Associate Editor

CONSULTING EDITORSHomer L.Davidson, TV Servicing ConsultantVictor Meeldijk, Components ConsultantJohn E. Shepler, Audio ConsultantSam Wilson, Electronics Theory Consultant

PRODUCTIONElizabeth Ryan, Art DirectorBarbara Terzo, Associate Art DirectorSusan Reale, Assistant Art DirectorEdmond Pesonen, Electronic Composition Mgr.Dorothy Kehrwieder, Production ManagerEmily Kreutz, Assistant Production ManagerPat Le Blanc, Photolypographer

BUSINESSRichard A. Ross, PublisherJohn Dorr, General ManagerFrank V. Fuzia, ControllerSimon Schatzmann, Circulation DirectorCatherine Ross, Circulation ManagerMelissa Nitschke, Operations ManagerCarol Licata, Data ProcessingDenise Pyne, Customer Service

SALES OFFICEElectronic Servicing & Technology76 N. Broadway, Hicksville, NY 11801516-681-2922; FAX 516-681-2926

Diane G. Klusner, Director of AdvertisingEmily Kreutz, Sales Assistant

EDITORIAL CORRESPONDENCE:P.O. Box 12487Overland Park, KS 66212913-492-4857

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NESDAMember. Electronic Servicing

Dealers Association

Electronic Servicing & Technology (ISSN 0278-9922) ispublished 13 times a year by CO Communications, Inc. 76N. Broadway, Hicksville, NY 11801. Telephone (516) 681-2922. Second class postage paid at Hicksville, NY andadditional offices. Subscription prices (payable in US dol-lars only): Domestic-one year $24.75, two years $45.Foreign countries-one year $30.75, two years $57. Entirecontents copyright 1995 by CO Communications, Inc.Electronic Servicing & Technology or CO Communica-tions, Inc. assumes no responsibility for unsolicited man-uscripts. Allow six weeks for delivery of first issue and forchange of address. Printed in the United States ofAmerica.

Postmaster: Please send change of address notice toElectronic Servicing & Technology, 76 N. Broadway,Hicksville, NY 11801.

CO Communications, Inc. is publisher of CO The RadioAmateur's Journal, Popular Communications, Micro -Computer Journal, CO Radio Amateur (Spanish CO), COAmateur Radio Equipment Buyer's Guide, CO AmateurRadio Beginner's Buyer's Guide. Popular Communica-tions Communications Guide, and Electronic Servicing &Technology.

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General software for the servicecenterBy The ES&T Staff

The introduction of the personal com-puter into our daily lives, both businessand personal, has wrought many pro-found changes; so many that most of uscan't really begin to appreciate them. Al-most all small businesses now have atleast one personal computer to handlecustomer contact information, keep trackof inventory, perform accounting chores,and more. Organizations such as church-es use the personal computer to performmany of these same types of functions, aswell as to publish the weekly bulletin. Athome, people are using their computersto track their family finances, store andretrieve recipes, play video games, writeterm papers, and even to keep track ofJunior's Little League batting average.

The computer is ageneral-purpose machine

The computer is able to perform all ofthese functions because it is truly a gen-eral-purpose information processing ma-chine. Its ability to handle information islimited only by the power of the proces-sor, the size of both temporary and per-manent memory, and the skill and imag-ination of the programmers who write thecomputer software.

In several past issues we have pub-lished articles about specific types of soft-ware. In one issue, for example, we talkedabout service center management soft-ware. In another issue we reported on di-agnostic software.

The utility of the personal computer tothe consumer electronics service businessis not limited to those two types of soft-ware. There is a host of personal computersoftware, much of which was writtenwithout regard to the needs of electronicsservice, that nevertheless can be very use-ful in the service business. This articlewill look at a few of those products. We'llbriefly mention such software as wordprocessing, database and spreadsheet, butthen place emphasis on products like elec-tronics circuit diagnosis and design andcomputer -aided drafting (CAD).

The big three

Most individuals as well as businesseshave a need to communicate on paper, tostore and retrieve data, and to performmathematical calculations. The personalcomputer is ideally suited to do all ofthese things, and programmers have de-signed many types of software to make itrelatively easy for computer users to dothem. Many companies have huge re-sources dedicated to devising and im-proving these types of programs.

Word processingPerhaps the single most popular appli-

cation of the personal computer is wordprocessing. These programs allow theuser to type up letters and other corre-spondence on the computer and save themin memory until it's time to print them. Italso allows the individual to make cor-rections to the material before the page isever printed, so even the least adept typ-ist can turn out perfect looking material.

But that's only part of what a wordprocessor can do. Because the softwaremanufacturers employ a wide variety oftalent, many word processor softwarepackages have a broad array of features,such as pre -formatted pages, graphicscapability, type available in a variety ofsizes and styles. So the user can call up acertificate, design a letterhead or formata newsletter.

Some of the more popular examples ofword processor software are Word Per-fect, Word Star, and Word.

Spread sheetSpread sheet programs, such as Lotus

123, Microsoft Excel and Quattro Pro, areextremely useful for anyone who needsto perform calculations in columnar fash-ion. The screen representation of the pro-gram consists of an array of horizontalrows and vertical columns. The intersec-tion of a row and a column is a "cell." Youcan enter numbers in cells, and then usethe program's functions to operate on thecontents of the cells.

For example, if you enter several num-bers that you want to add together, suchas household expenses, then you can entera formula into another cell that will givethe sum of those numbers. If you wantedto, you could also take the mean, the mode

or the average of the numbers.A spread sheet is particularly useful for

doing what accountants call "what if'types of calculations. For example, let'ssay you work out a business plan for nextyear based on increasing your volume bysome percentage, and assuming a partic-ular inflation rate, you can then go in andchange those percentages and all calcula-tions based on those rates will change.

Data baseData base programs, such as dBase,

Paradox, and Lotus Approach allow theuser to store data and manipulate it in any

depending on theexperience and skill of the user. Manydatabase applications, such as service cen-ter software management programs, arebased on one of these software packages.

Electronic circuit simulationSome computer software programs al-

low the user to actually design a circuiton the computer screen and test it to seehow it works. For example, there's a pro-gram called Electronics Workbench byInteractive Image Technologies that con-tains not only symbols for typical elec-tronics components that can be hookedtogether, but it also has simulated testequipment on the monitor screen that canbe connected to various points in the sim-ulated circuit to read parameter values.

To start building the circuit, the usermoves the mouse over to the "parts" sec-tion of the screen, clicks on the resistor,capacitor, or whatever, and drags it to theworkspace on the screen, then drops it andruns "wires" to it. If the circuit gets toobig for the screen, simply scroll and keepbuilding. Because the wires are routedautomatically, and a grid is available,even complex circuits are readable.


All commands can be issued from sim-ple menus with a mouse, and commonoperations have keyboard shortcuts. Youcan cut, copy and paste groups of com-ponents, or put components into a sub -circuit, a kind of "black box." It's evenpossible to put one subcircuit inside an-other to simplify complex circuits. Sub -circuits can be used simultaneously inmany places in a circuit and stored forlater use.

PartsSimulated ideal and real -world circuit

components, available from a "bottom-less" bin include resistors, capacitors,inductors, relays and transformers. Theuser has precise control over their values.Active components include diodes, Zenerdiodes, NPN and PNP BJTs, op amps,JFETs and MOSFETs. Voltage controlledand current controlled as well as inde-pendent sources are included. The partsbin also contains voltage and current con-trolled manual and time delay switches.

Ideal and real -world modelsFor each active component, you can use

either an ideal or real -world model simi-

lar to those found in data books. An idealop amp, for example, has a near -infinite,open -loop gain and slew rate. The partsbin also provides a selection of real -worldop amps that take into account the unity -gain bandwidth, input -bias and offset cur-rents, etc.

Instead of an ideal op amp, you can se-lect, for example, an LM741 from themodel list. The analog module also in-cludes an editor to investigate or alter anyof the models, or to create your own. Editor create your own models for op amps,BJTs, diodes, JFETS and MOSFETS.

Test equipmentThe program has a function generator

that produces square, triangular or sinu-soidal waves. The user controls the fre-quency from 1Hz to 999MHz, the dutycycle, amplitude and dc offset.

A simulated dual -trace oscilloscopebehaves like the real instrument. It sup-ports internal or external triggering oneither the positive or negative edge, andthe time base is adjustable from secondsto nanoseconds. You can even study hys-teresis by plotting the signal amplitude onthe axes.

The simulated autoranging multimetermeasures current, voltage, resistance anddB loss. You can measure a signal's dc orac component.

SPICE simulationOnce you have designed the circuit,

you can switch on the "power" and theprogram simulates the response of the cir-cuit, using the international standardSPICE algorithm. The user has completecontrol over all parts of the circuit, as wellas over SPICE models used to simulateactive components. When a signal is firstapplied to a real circuit, there is a short-lived transient state before the circuit set-tles down to its final response. This soft-ware can be configured to present eitherthe transient or the steady state.

Digital module

This program also offers a digital mod-ule with which you can design digital cir-cuits. The parts bin contains an endlesssupply of ideal components. The selec-tion of logic gates includes AND, OR,XOR, NOT, NAND and NOR. The selec-tion of flip-flops includes RS, JK(clocked, negative -edge -triggered) and D

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February 1995 Electronic Servicing & Technology 7

(positive -edge -triggered). There are alsohalf -adders, seven -segment displays,switches and LED probes.

The test functions for the digital mod-ule include a word generator that drivesa digital circuit by producing streams of16 -bit words and a logic analyzer.

Educational featuresA service center could use this type of

software for educational purposes. Forexample, if one of the technicians shouldneed training or a refresher on any typeof circuitry, the service manager could sethim up with a computer with this softwareon it and let him study on his own.

Another feature of the software, how-ever, is that the individual who controlsthe computer; instructor, service manag-er, or whoever, can introduce real worldfaults. For example, any component canbe open -circuited or short-circuited, in amanner that's hidden from the student togive him troubleshooting experience.

DraftingAnother type of software that may be

of value to service centers is drafting soft-ware. Every service center uses schemat-ic diagrams in one form or another, and

from time to time may have a need to drawpartial diagrams of a TV or VCR or otherconsumer product.

Many times, such hand drawings do notvery well convey the desired informationbecause they're not clear and sharp. Adrafting software package allows anyonewho owns a personal computer to producefirst class drawings, and not only of sche-matic diagrams, but of buildings, floorplans, and anything else that lends itselfto drafting techniques.

There are a number of drafting pro-grams available: Drafix, AutoCAD,CADKey and many more. We will useDrafix, one familiar drafting program , topresent an idea of what can be done withone of these drawing packages.

The screen for Drafix for Windowscontains a workspace on which to draw,and a number of items that you can draw,including lines, double lines, curves,polygons, ellipses, arcs and circles, and ahuge set of symbols. The program con-tains symbols for use in all kinds of draw-ings: architectural, mechanical, land-scape design, network layout and elec-trical/electronic. It would be impossibleto do justice to a program like this in justa few pages in a magazine, so we won't

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even try. We'll just try to give an idea ofhow it's used.

Creating a drawingTo draw a line for example, once the

program has been run, the user moves themouse to point to the "Draw" menu item.This causes a submenu to drop downshowing a number of choices. In this case,the user selects "Line," which causes afurther submenu to open, allowing theuser to select from among "Single," "Dou-ble," and a number of other choices.

If the user wants a single line, he choos-es "Single." Now when the user movesthe mouse, a cursor appears on the work-space that shows the location where theline will start. The user chooses a spot tobegin the line and presses the left mousebutton. Then the user moves the mouse tothe point where he wants to end the line.As the mouse is moved, a "rubber band"line follows the mouse from the startingpoint to show what the finished line willlook like once the button is pressed. Whenthe mouse is at the desired point, press-ing the left button again finishes the line.

To draw a symbol, the user chooses alibrary of symbols, then using a series ofmenu choices places the symbol such asa resistor, capacitor, inductor, transform-er, transistor, or whatever, in the drawing.If the symbol library doesn't have thesymbol you need, you can draw your own.

The program also provides for typingin callouts to identify the components inthe drawing. Large drawings can bespread across a number of screens. Com-plex drawings such as building drawingsthat contain architectural features, plumb-ing/piping information and electrical lay-outs can be drawn in a number of layersso that the user can look at any one of thelayers, or any combination of layers.

The computer can helpComputers and their software have def-

initely changed the way people do theirjobs. They provide a number of featuresand functions that allow people to auto-mate the work to be done and to look atthe information they need to process in avariety of new ways. Consumer electron-ics service centers have such a broad vari-ety of information processing needs thatservice center owners and managersshould be constantly on the lookout forsoftware such as that mentioned here thatcan help them do their difficult jobs.

8Circle (40) on Reply Card

ProductsCAD for Windows

Foresight Resources Corporation an-nounces Drafix CAD Professional ver-sion 3.0 computer -aided drafting soft-ware, designed to exploit the multipledocument interface, object linking, built-in help and other features available in thelatest version of Microsoft Windows.

This package includes the entire collec-tion of symbol libraries as well as hun-dreds of sample designs and drawings.

The software improves both perfor-mance and the ease of user interaction byexploiting new features that are availablein the latest release of Windows, includ-ing OLE 1.0 server technology, DDE,Windows Clipboard and support for rightmouse button functions. By clicking theright mouse button special menus appearthat intuitively anticipate what functionsthe user is most likely to need next. Inaddition, as the cursor passes over a tool,new pop -balloons appear to assist usersby announcing its functionality.


PC diagnostic and POST readerMicro -Scope, from Micro 2000, is a

complete diagnostic tool for testing mem-ory (base, extended, expanded, andcache), fixed drives (MFM, RLL, SCSI,ESDI, and IDE), floppy drives, serial andparallel ports, system board, and more.

Version 6.0 adds more than one hun-dred tests and enhancements to the pre-vious version. New features include:identification of exact processor (180486Rev. 08, etc.); identification of exact man-ufacturer of components; enhanced IRQand DMA testing; testing of specific seg-ments of memory; generic FIFO tests forserial devices; video memory test of up to4 megabytes; string search option formemory, floppy, and hard disks; accuratebenchmarks for processor, coprocessor,memory access time, hard disk seek time,and video transfer rate; enhanced paralleldevice tests; real time clock tests; ex-panded IDE drive tests; keyboard tests;mouse tests; Soundblaster and Adlibtests; speaker tests; CD ROM tests; joy-stick tests; printer tests; and more.

The POST -Probe reader card, alongwith its MCA adapter, will fit into anyISA, EISA, or Micro -Channel slot andmonitor the system as it's trying to boot.

It displays all the diagnostic signals si-multaneously. You can watch all comput-er functions as they occur, allowing theuser to isolate problems even if the sys-tem BIOS does not emit POST codes. Themanual includes all the POST codes onthe market, lists the code, the test that isfailing, and what chip or device is caus-ing that test to fail. The card features a tri-state logic probe built in. making deter-mination of specific chip failure possible.

The Universal Diagnostic Toolkit in-cludes both the Micro -Scope and POST -Probe diagnostic tools.


Fast recovery soldering stationAmerican Hakko's Model 929-2 sol-

dering iron was especially developed toprovide fast recovery of heat to solder-ing tips as well as reducing the necessi-ty for their frequent replacement. Bothfeatures provide greater control.

The unit has an integrated tip/sensor

heating element that directly transfersheat to the tip, permitting faster responseto temperature fluctuations, thus creatingbetter solder joint quality and improvedstart-up time.

The station uses tips that last longerthan most high performance irons on themarket, according to the manufacturer.Tips are available for applications rang-ing from fine pitch to heavy groundplane. The new tip design also makes tipchanging safe, quick and easy.


Electromagnetic field testerA. W. Sperry Instruments, Inc., a lead-

ing national marketer of portable electri-cal and electronic test equipment, an-nounces the introduction of their Electro-magnetic Field Tester, EMF-200A.

The tester uses a state-of-the-art digital

Electromagnetic FieldRadiation Tester

display. Measurements are precise andeasy to read.


On-line service helps locatecomputer equipment

MicroLine, Inc., has developed an elec-tronic information service dedicated tocompanies in the computer service indus-try. The company's on-line databases as-sist computer resellers, MIS maintenancemanagers, and corporate purchasingagents in quickly locating the most cost-effective sources for computer equipment,repairs, exchanges, and spare parts.

These databases contain information onover 1000 vendors and 100,000 partsnationwide. Users call into the company'shost computer through their modems andperform product specific searches basedon a keyword description, manufacturer'sname, or model number. They instantlyreceive up-to-date and accurate informa-tion on vendor pricing, warranties, turn-around times, addresses, contact names,phone numbers, detailed vendor informa-tion and terms and conditions.

The company's other services includeclassified ads for buying and selling com-puter equipment and services, repair spe-cials, user networking/support confer-ences, electronic mail, and intemet mail.There is a flat yearly fee to use all the ser-vices on the system. New subscribers geta free 14 -day trial of all these services.


February 1995 E:ectronic Servicing & Technology 9

O

One thing that consumer electronics ser-vicing technicians can always count on isthat engineers and manufacturers willconstantly be improving the electronicsproducts that consumers buy and that willappear on the service bench. In addition,the manufacturers can be counted on tocontinue to come up with new electron-ics products, and to continue to add elec-tronic features to otherwise non -electron-ic products.

Here are some technological innova-tions that readers might be interested inreading about.

Optimizing tape recordingHigher grade tapes are capable of pro-

ducing a sharper picture than are lowergrade tapes. High grade tapes are capableof recording and playing back small am-plitude changes resulting in an improvedpicture. This increase in detail is not pos-sible on lower -grade tapes.

On most VCRs the difference in pic-ture between low and high grade tape isnot apparent. The operating parameterson most VCRs are designed to producean acceptable picture on low-grade tapes.Therefore the picture improvement pos-sible on higher -grade tapes is not used.

Four VCRs in Mitsubishi's new prod-uct line incorporate a new feature calledPerfecTape. The PerfecTape feature de-termines the quality of the tape and ad-justs the internal circuitry to produce thebest possible picture.

There are two operational modes for thePerfecTape feature: automatic and man -

NewtechnologyupdateBy The ES&T Staff

ual; selectable from the Option Menu.In the automatic mode, the evaluation

of the tape quality is activated when a cas-sette is first inserted in the VCR. In themanual mode, evaluation of the tape qual-ity may be activated after a tape is in theunit by pressing the PerfecTape button.

The evaluation process requires mo-mentary recording. To preserve any pre-viously recorded information, the VCRautomatically prechecks the tape for pre-viously recorded CTL pulses before theevaluation process begins.

Ghost cancellationSpurred by the growing acceptance

among broadcasters of the Philips televi-sion ghost cancellation system, PhilipsConsumer Electronics Company hasformed a new unit responsible for world-wide marketing and manufacturing forthe industry's first consumer and profes-sional products in a new category.

The specialty Television ProductsGroup, based in Knoxville, TN, is respon-sible for continuing the rapid implemen-tation by broadcasters of Philips GhostCancellation Reference (GCR) signaltechnology, including sale and installa-tion assistance to terrestrial and cable net-works and local stations. Last July, theFCC designated Line 19 of the verticalblanking interval solely for broadcastingof this GCR signal. The signal, inventedat Philips Laboratories, Briarcliff Manor,NY, has also been recommended as theworld standard by the International Tele-communications Union, while the Euro-

pean Broadcast Union has agreed to ad-dress specific standards for applicationlater this year.

In addition to ensuring full acceptanceby broadcasters of Philips GCR technol-ogy, the Specialty Television ProductsGroup is responsible for the manufactureof several planned products, including aset -top GCR signal decoder with built-intuner, a similar decoder without tuner foruse with virtually any brand of VCR orcable box; a set -back decoder for use withthe company's projection televisions al-ready available with dedicated GCRjacks; a low-cost GCR inserter, and vari-ous accessories. Philips plans to marketthe set -top, ghost -canceling decoders toconsumers in early 1995.

In addition to ridding NTSC televisionbroadcasts of the annoying ghosts thathave plagued color TV signals since theadvent of the medium, the GCR technol-ogy offers additional improvements tosolving multi -path problems such as colorfading and mis-registration.

Computer networking via cable TV

Education takes a major step toward the21st Century through an innovative effortinvolving Zenith Electronics Corporationand Tele-Communications Inc. (TCI),linking an entire Indiana school district toa new networking system that offers high-speed, low-cost data access throughoutthe district on the cable TV system.

The new communications link servingthe Evansville-Vanderburgh School Cor-poration in southern Indiana, eventually


could lead to an interactive educationalnetwork with creative applications suchas work -at-home and distance learning.

"In addition to increased access speed,our long-range vision is to move infor-mation and video between schools. Thistechnology lends itself to that," said MikeRuss, director of technology for Evans-ville-Vanderburgh. "We needed and founda system set up to help us tap into newand unexplored possibilities for educa-tion in the future."

Using existing TCI cable TV lines andZenith's Channel Mizer, a premises de-vice that connects baseband Local AreaNetworks (LANs) to cable systems, all 40Evansville-Vanderburgh sites (37 ele-mentary schools, high schools and ad-ministrative facilities) were linked in Au-gust, making it the largest school -widenetwork in the country.

The system currently offers school ad-ministrators and teachers such applica-tions as sharing district -wide informationand reports, grade transferring and send-ing E-mail. Ultimately, this network canbe expanded to include a computer -based,educational network that can link stu-dents through a PC, a modem and a reg-ular cable TV in their home. The network

effectively eliminates telephone linesfrom being tied up and splitting in -homeTV channel use.

"Interactive services such as distance -learning and work -at-home can introducea more collaborative, cooperative form ofeducation. That may mean a majorchange in the way we think of school andhow to teach students, but this emphasiscan better prepare students for the realworld, where we all have to work effec-tively with other people," Russ explained.

"Also, this technology allows us tobring more of what students are exposedto outside of the classroom back into theclassroom, which hopefully can raise theenthusiasm for education. It can makeschool a fun place to be," he added.

Rich Killmar, manager of showcase/model school for TCI, said, "the potentialof this network is only limited by the cre-ativity and imagination of the school dis-trict using it. Because it is so flexible andexpandable, access such as teacher -to -student, student -to -student, or student -to -school opens a wide range of uses."

Applications such as access to schoolresources like the library, encyclopediasand other reference materials, linking intospecific classes not offered at an individ-

ual school, the addition of more advancedclasses for gifted students and after -school access to the teacher, are just a fewpossibilities this type of network makesavailable, he said.

These and other programs can easily beadded to the overall district curriculum byutilizing a variety of Zenith gatewayproducts, including HomeWorks, a low-cost PC LAN interface and CATV datamodem that provides LAN connectivitythrough standard home subscriber cableTV facilities.

Microwave clothes dryerIn November, the Electric Power Re-

search Institute (EPRI) announced thedevelopment of a microwave clothes dry-er, one that keeps pace with the washer sothat people spend less time doing laundry.Actually, the dryer has two designs: onefor residential use and another for com-mercial application. The prototypes re-cently completed nine demonstrationshosted by EPRI member utilities.

"A survey of 220 people at one of thedemonstrations of the residential unitshowed that 81 percent thought that theshorter drying time was the most attrac-tive feature of the dryer. Eighty-six per-

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cent said that they would be interested inbuying the dryer, if it were availabletoday, even if it cost 20 percent more thanconventional dryers," said John Kessel-ring, manager, residential systems, ofEPRI. Commercial availability is not ex-pected for several years.

The residential dryer dries clothes one -sixth faster than conventional dryers. Be-cause more power is availabe at com-mercial sites, the commercial dryer workstwo-thirds faster. Both dryers are approx-imately 15 percent more energy efficient.

About 40 percent of the clothes thatrequire dry cleaning could be dried in themicrowave dryer without shrinkage ordamage. The microwave clothes dryer isgentler on fabrics because it targets watermolecules, rather than the molecules ofthe clothes fabrics. Moisture is removedmore quickly, gently and at cooler tem-peratures than in conventional dryers.

Because of the design of zippers andmetal buttons they are not susceptible toheating. To avoid any possible hazards,Thermo Energy Corporation, EPRI'scontractor, is developing a safety systemto automatically shut the machine off andnotify the user if something heats the fab-rics or starts to degrade.

Kesselring hopes to first enter the on -premises laundry markets, such as innursing homes, hotels, etc., where a full-time operator checks for extraneous ob-jects. In the commercial sector, the avail-ability of sufficient electric service allowsfor a dryer with larger magnetrons forfaster operation. Also, loads of similar fa-brics, such as sheets and pillowcases, areeasier to dry.

The commercial sector could also ben-efit from using microwave clothes dryersby avoiding the use of dry cleaning fluid,which has suspected environmental andhealth impacts," Kesselring said.

The microwave clothes dryer operatesin three drying modes: cooler, faster, andmore efficient. With cooler drying, onlymicrowave heating is used with not wasteheat recovery. This is the mode that al-lows woolens and delicates to be dried.Faster drying combines microwave heat-ing with conventional electric resistanceheating. More efficient drying combinesmicrowave heating and recovery of mag-netron waste heat.

"It's clear that the microwave clothesdryer will be a winner because of userconvenience, environmental benefits andefficiency," said Kesselring.

EPRI, founded in 1972 and headquar-tered in Palo Alto, CA, manages technol-ogy research and development programsfor the electric utility industry to improveelectricity production, distribution anduse. Some 700 utilities are members ofthe Institute.

Implications for serviceEvery technological advance in the

area of electronics has potential implica-tions for service centers. Improvementssuch as PerfecTape and the ghost cancel-lation reference signal introduce new cir-cuitry that service technicians need to beaware of in servicing the products. Inno-vations such as networking via cable TVintroduce entire new technologies thattechnicians may one day encounter.

Many consumer electronics servicecenters began servicing what was essen-tially an appliance when microwave ovenswere introduced. Microwave clothes dri-ers might become another similar oppor-tunity when they become available.

Keeping abreast of these technologicaladvances can help a successful servicecenter remain that way or become evenmore successful.

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Circle (29) on Reply Card12 Electronic Servicing & Technology February 1995

Ten steps to successful servicingBy Brian Phelps

If you break servicing down into steps,you'll see that most service jobs requirethe same steps. You might try to skip astep or two, but doing so often leads tomore work later, as you have to back upand re -do the skipped steps.

You can follow these steps without thevideo test instruments, but they will bemore difficult, will call for more compo-nent -level testing, and will often causeyou to backtrack because you followedthe wrong circuit path.

Here are the 10 steps used by success-ful servicers:

1. Ask customer for symptoms and his-tory of item being repaired

2. Do performance test with customer3. Determine all related symptoms4. Check for obvious defects5. Narrow problem to functional

block/defective stage6. Pinpoint bad components7. Replace bad components8. Re -test to confirm operation restored9. Repair secondary symptoms10. Run complete performance test

Let's look at these steps, so that you canunderstand why each is important.

Ask the customer forsymptoms and history

Many servicers get a chuckle about thisstep. Often times, they explain, the onlyclue they get from a customer is, "It quitworking." While this is all they get fromsome customers, the set's owner can oftenfill some gaps in the diagnosis process.

Notice that this step asks for two kindsof information, symptoms and history. Ifthe customer can explain the exact symp-tom, such as, "The picture went first, thenthe sound," you can get an important clueabout the mode of the failure. Moderntelevision receivers often appear to workfine one moment, and then fail to start thenext time, so "It doesn't work" might beall the customer knows.Phelps is the Electronic Service Center Product MarketingSpecialist and Business Management Solutions (software)Manager for Sencore Electronics.

Don't forget to ask about the set's his-tory. Did it do this before? Has it beenfixed by another shop? If so when andwhere? Were there any unusual symp-toms in the week or month before the fail-ure, such as popping in the audio or sparksin the picture? Was there a thunderstormin the area recently? All these clues canbe especially helpful when tracing anintermittent or unusual failure.

Do a performance testwith your customer

Few technicians bother with this step,yet some of the most successful servicecenters tell us that it's the most important.With the customer watching, plug the setinto a live outlet and run through everyfunction to see what works and what doesnot. Sometimes, you'll find there's reallynothing wrong - the problem is a dead acoutlet, a bad antenna, or a disconnectedcable -TV tap.

But there's an even more important rea-son to run through a complete perfor-mance test. The set may have more thanone problem and the customer has onlymentioned the most recent one. For exam-ple, they may be complaining about theloss of horizontal sync, but your testshows that audio is also weak. Or, theymay not have noticed the low brightnesscaused by a weak picture tube, and maybe glad to learn that you can restore thepicture tube with both a quality CRT testerand restorer.

Video test instruments let you test theperformance of every TV circuit by con-necting to the antenna terminals. Youdon't even need to take the back off theset to do these tests.

Most importantly, doing this perfor-mance test shows the customer that youare concerned about doing the job cor-rectly. You've taken the time to show thatyou want to do a complete job.

Before the customer leaves your shop(or before they leave the room if you'redoing home service), have them agreewith you on what they want fixed. Youand your customer come to an agreement

on such questions as whether they wantthe picture tube restored, or whether thereare some other, secondary problems theywant you to look at. By pointing out thatthere are several, unrelated problems, it'seasier to itemize the bill. Otherwise, theymay think that all your work was to findonly one problem, and may feel you areovercharging them when the final bill ispresented to them.

Determine all related symptomsHere's one of the steps where many

technicians build in their own inefficien-cy. Instead of identifying all the symp-toms, they find one symptom and begintracing it. But, this symptom may be a sec-ondary symptom of an even larger prob-lem. If they had taken a few moremoments, they might have noticed thattwo or three symptoms all point to thesame source, such as a bad tuner, or poor-ly regulated power supply.

If you use all the features of your testinstruments, this step becomes easy. Theinformation gained from the performancetest in step 2 already has identified themain symptoms. Now, it's a matter ofrefining these symptoms, by making amore detailed test, or by using some ofyour instrument's functions not usedwhen doing the simple performance test.

If you confirm several symptoms, youneed to decide which one to troubleshootfirst. You should not try to follow morethan one at a time, because it is too easyto get crossed up as one affects the other.Since one problem may cause multiplesymptoms, finding one bad componentoften clears up all the symptoms. Alwaysrepair circuit problems in the followingorder, to find the problems most likely toaffect other circuits:

1. High Voltage

2. Sweep

3. Sync

4. Luminance (video)

5. Color

6. Audio


Figure 1. Checking for obvious defects can save troubleshooting time.

Each of these general symptoms directsyou to one of the areas of the "troubletree" troubleshooting guide (availablefrom Sencore). They, in turn, let you iso-late the defective stage for troubleshoot-ing in three steps or less.

Check for obvious defectsThis step relies on your senses of obser-

Figure 2. Injecting a vido signal can help narrow the problem to a sin-gle defective functional block.

vation and your own practical experience.If, for example, you see a burned resistor,or smell smoke, you should attend to theseobvious defects, even before making ameasurement. Sometimes repairing theburned part solves the problem. But, evenif it doesn't, you have fixed somethingyou know must be corrected before theservice job is done.

You may also know that a particularchassis has a manufacturing defect whichcauses a particular symptom. Service lit-erature, for example, may instruct you toresolder certain connections, or to replacecertain components with improved ones.Here again, checking for these obviousdefects first, ensures that they won't mis-lead you in your final troubleshooting.

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Narrow the problem toone functional block

Up to this step, the video test instru-ments have been used to make generaltests. Now, it's time to put their full ana-lyzing capabilities to work with func-tional analyzing. Functional analyzingmeans that you base your troubleshoot-ing on the function of a circuit, instead ofthe specific parameters of each compo-nent in the circuit.

Functional analyzing calls for a dupli-cate of the normal signal into each of thestages you think might cause the symp-tom identified earlier. You know thatthese substitute signals are good, so youknow that injecting them into a good cir-cuit causes it to operate normally.

If you inject a signal into a test point,and the symptoms improve, you know thatall the circuits from there to the output areworking correctly. If, by comparison, thesymptoms remain, you know that the badcircuit is affecting the substituted signal,and the problem is found to be somewherebetween the injection point and the output.

If you use the "divide and conquer"troubleshooting method, you'll find thebad stage in four troubleshooting stagesor less (steps 3-6 above).

The principles of divide and conquerinstruct you to substitute into a test pointabout half -way through the circuits relat-ed to the symptoms. If the symptomimproves, you have proven that all the cir-cuits to the output are good, so you movetoward the input. If the symptom remains,you are ahead of the bad stage, so you areinstructed to move toward the output.

In either case, the troubleshooting stepsdivide the remaining stages in half again.This halving process repeats until youhave found the bad stage. You know youhave the bad stage when you get animprovement in the symptom wheninjecting at its output and the originalsymptom when injecting at its input. Theisolated stage has only a few parts thatmight be bad. These are tested with con-ventional testing methods.

Pinpoint bad componentsAfter you have isolated the problem to

a single stage, bring in your convention-al testers. You might use a scope or wave-

form analyzer to look at a signal. Youmight use your volt/ohmmeter to measurea resistor or to test a power supply. Youcan use a Z Meter to test a capacitor or aninductor, or you can use a transistorchecker to test a transistor.

Whichever test method you use will bemore effective, since your video testinstruments have narrowed the suspectparts to a dozen or less. Functional ana-lyzing has isolated the problem stage sothat your conventional tests are moreeffective than ever before.

Replace bad components

This step doesn't directly involve testinstruments. It is a good idea, however, touse your component testing methods tocheck parts associated with the bad partyou found. For example, don't forget tocheck emitter resistors if a transistor wasbad. Also, look for shorted PC boards, badsolder connections, and other mechanicalproblems.

Re -test to confirm operation restored

Changing a part may only partly return

normal operation. Double check yourwork by feeding in the video test instru-ment signals which dynamically test thecircuit associated with the original prob-lem. The video patterns produced bysome video test instruments providedynamic tests you can interpret right onthe screen of the TV you are testing.

If your tests show there is still a prob-lem, use signal substitution to find itscause. This time, start at the input of theoutput of the circuit you just repaired tolearn whether another part in the same cir-cuit might be defective.

Repair secondary symptoms

If repairing the first problem did notclear up secondary problems, you nowturn your attention to them. Move back tostep number 3, and follow the trou-bleshooting sequence to find eachremaining problem, one at a time.

Run complete performance testWhen you have found all the problems,

repeat all the steps of the performance testused at the beginning of the process.

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SONYCircle (39) on Reply Card


VCR service centers: Some tips onremaining profitableIt\ it% nu It. ( ; ham

Making money in the electronics servic-ing business has required many changessince the TV repair/tube tester days of the50's, 60's and early 70's. Even the earlydays of $750 to $1,000 VCRs were goodfor the electronics service business. Re-pair quotes of $75 or $150 were thoughtto be a good deal, and these older ma-chines were designed to be repaired; so,it wasn't a frustrating experience for thetechnician. But now many consumers arethinking of the VCR as a disposable appli-ance, like an alarm clock or telephone.

The arithmetic of VCR servicingAre service centers still able to make

money servicing VCRs? Yes, but it is alot tougher these days and many service

Graham is Sales Manager of Tentel

centers won't survive the transitioncaused by the low-priced new units avail-able on the market. We've talked withthousands of servicers over the years, andit's been interesting to note the differ-ences between service centers that makemoney, grow, and stay in business, versusthose that don't make money, dwindle,and end up with disconnected phone linesleaving "no new number."

From the thousands of technicians andservice center owners we've talked withover the past few years, here's our outlinefor a profitable VCR service business.

Charge for estimatesCharge $20 to $30, depending upon the

area of the country and local cost of liv-ing. If you do free estimates, the customermay continue to shop around for the low-

est repair cost and the machine may notmake it back to your service center, evenif you were the low bidder.

Unfortunately, those who don't chargefor estimates often don't have a very wellequipped service area, and you may loseout to someone with not much more testequipment than a multimeter and needlenose pliers. Charging for the estimate alsoprovides a source of repairable VCRs,since the customer often chooses to aban-don his VCR instead of going ahead withrepairs. You either get the estimate fee,the repair job, or the VCR, so at least youaren't working for free.

Provide a knowledgeableaccurate estimate

You might call this a "technical evalu-ation" rather than an estimate, because

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16Circle (25) on Reply Card

that's really what it is. The fact is the me-chanical parts of the VCR do wear out. Ifyou review any factory service manual,you'll see that such mechanical parame-ters as hold back tape tension, take-uptorque, FF torque, rewind torque, reel ta-ble heights, guide heights and other sim-ilar measurements represent the basics formechanical performance of a transport.

If you're using a "trial and error" meth-od, it will prove to be too prone to errorsand too time consuming. Often there areseveral marginal problems along with theobvious problem. Conscientious as youmay think you are, the guessing that isnecessary without proper test equipmentwill help assure failure.

Test equipment will allow an accurate,true estimate in the least amount of time,plus this same test equipment can be usedto help perform the actual repairs.

The ability to measure the actualamount of video head tip protrusion(wear) has proven to be one of the mostimportant parameters for determining notonly how much use the machine has al-ready had, but more importantly howmuch longer it's likely to last. Accuratelyknowing video head wear allows you to

honestly advise a potential customer that;"even though the machine is six (or what-ever) years old, the heads are still in verygood shape and should last for six (orwhatever) more years, once these 'other'problems are corrected."

Having information like this helps as-sure the customer that you know whatyou're doing and that his machine will befixed correctly by an expert. We recom-mend the use of a check out form to compile findings regarding these critical elec-tronic and mechanical rests. The formprovides an excellent method of showingexpertise to the customer, and helps tofully explain and justify repair estimates.It can also be maintained as a history asfuture machine problems arise. This leadsus directly to the warranty on your work.

Pros ide a six-month to one-yearwarranty on VCRs you service

I'm always amazed at how many tech-nicians tell me that they only offer a 30 -day warranty, just on their work, but thencomplain about lack of business. Shouldit really be a surprise? New machines of-fer a one-year warranty, even longer whenpurchased on a number of different major

gold credit cards. The customer has toweigh the cost of $150 for a new machinewith a one or two year warranty versus$65 (national average) for a "how manyday warranty?"

If you are able to quickly and accuratelymeasure all of the normal wear items in atransport, including video heads, tape ten-sion, torques, etc., why couldn't you offera six-month warranty, or as you discoveryour repairs getting better, a one-yearwarranty on the VCR? (Exclude lightning,small kids, fire and problems outside ofthe normal wear and tear category).

Even if you see 5 or 10 percent of thesemachines back within the one-year timelimit, the extra business will more thanoffset the extra work required to correctthe problems in these few machines. Youmay be pleasantly surprised to find thereturn percentage to be far less than 5 per-cent when you eliminate guessing aboutmechanical wear and think about the goodwill you will reap.

Make money on abandoned VCRsA fair percentage of customers will

choose to abandon their VCR after theyhear the repair estimate. This may actual -

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4 Here's what you'll find:"Dip -and -brush" cleaning with

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" Using too mild a solvent and wastinghours cleaning. Complaints about residues, smellsand slow drying. Out-of-date safety sheets. And more.

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Circle ( 2) on Reply CardFebruary 1995 Electronic Servicing & Technology 17

ly be good news. You may make moremoney on these VCRs than if you had re-paired it for the customer. By repairing theVCR, and again offering a one-year war-ranty, you will find that selling thesemachines for$95 ($75 low -end to $ 150 fora high -end 4 -head Hi-Fi unit) to customerswho bring in their broken VCRs may helpboth your customers and your bottom line.

If you sell a reconditioned VCR for $95that would have brought $65 for repair,you make an additional $30 (plus youmay pick up his broken unit for free, sincethe customer now has a working unit andmay not want to pay to have his unit ser-viced). Being able to accurately measureremaining video head tip protrusion onthese reconditioned units will help to de-termine how much use they've alreadyhad, and thus how much more they'relikely to endure.

New heads typically protrude 40 mi-crons. When the heads are worn outthey're down in the 10 micron range. Aused machine with 25 microns remainingis in a totally different category than onewith only 15 microns. The warranty andprice may both be based on this number.

Find more businessYou may be doing lots of things right,

but if you don't have enough VCRs to ser-vice, you won't be profitable. Coupons inlocal TV program listings, although fair-ly expensive, have proven to be an excel-lent method to reach your target audience.

Other good programs we've heard of areflyers posted at video tape rental stores.

No one is more interested in propermechanical repairs than these store own-ers, since tape tensions, torques, guideheights, carriage latching problems, andsimilar problems, cause the vast majori-ty of their ruined tapes. Rental stores needto have access to a reliable repair shopsince they lose many tapes due to defec-tive VCRs.

You might want to offer a Saturday"clinic," where you set up in their storeand for $15 (or some nominal fee) cleanthe head (proper method, not just a clean-ing tape), measure hold back tension, afew critical torques, reel heights, guideheights, RF envelope, and for $5 moreyou can even measure their remaininghead wear. Even if their VCR is perfect,they'll know who to bring it to if theyexperience a problem.

If their VCR is in need of repair, you'llprobably be able to write up a ticket totake it back to your service center. Oftenyou can stay fairly busy just from wordof mouth of these "customers," since theycan now inform friends and family of an"expert" they know-you.

Another low-cost method of findingmore business is "discount" couponsplaced under windshield wipers at malls,baseball games, or anywhere there are alot of automobiles. Have coupons print-ed 3 or 4 up on an 81/2 x 11 sheet. Thisreduces cost and it appears more like a

discount coupon. Remember, almost ev-eryone has at least one VCR and mayknow others who are having problems.

Expensive products will be servicedDoing repairs properly, providing a

worthwhile warranty, and generating newbusiness is the only way you can remainprofitable in the current low -price VCRservice market. There are a growing num-ber of more expensive four -head and Hi-Fi VCRs and camcorders that will not beviewed as disposable, and most custom-ers who pay even $150 for a low -end ma-chine will look favorably at a $65 repairrather than another $150. The consumerelectronics service business should im-prove very soon with the new technolo-gies of wireless cable, flat -screen TV, pro-jection TV, and other high dollar con-sumer products that will help support theindependent servicer.

VCRs will certainly be with us formany years. There is no other method thatcan provide six hours of video recordingfor $2 or $3 even dreamed of at this time.The VHS format is also being used fortime-lapse recorders in conveniencestores, banks, etc., and due to the high datamemory, companies are also using it fordigital audio recording, and computerdata backup. Don't give up on VHS, butif you're going to be profitable doing ser-vice, perform the service correctly, andstand behind your work.

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tools for measuring TAPE TENSION (shown in every servicemanual), TORQUES (shown in every service manual), REELTABLE HEIGHTS, GUIDE HEIGHTS (you guessed it - everyone!) Yet 20% of the shops listed under VCR REPAIR in theyellow pages "disappear" each year, often because theycouldn't afford to do repairs right either! If you're expectingcustomers to pay you $65 (national average) for repairs ontheir VCR, maybe having the proper equipment to do repairs RIGHT would help.

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(916) 939-4114 FAXCircle (41) on Reply Card


Test Your Electronics KnowledgeTerms defined

By Sam Wilson

(Answers on page 59)

1. To deliver data to a medium such as storage

2. Another way of saying "the voltage between two points."D

3. A coil assembly that is used to produce electromagneticdeflection of the electron beam in a CRT.

Y

6. An expression relating the output of a linear systemto its input.

T

7. Another name for the television luminance signal.Y

8. A solution that conducts an electric current.E

4. A temperature scale equal to the Celsius scale- 273.18degrees. 9. A unit of energy equal to a thousand watts dissipated

K for one hour.K

5. A wire used for transmitting and receiving radio waves.A

Wilson is the electronics theory consultant for ES&T

10. Another name for a star -connected transformersecondary in a three-phase system.

Y

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Circle (31) on geply CardFebruary 1995 Electronic Servicing & Technology 19

Magnetic recording principles:Videolip Lamar ltilchie

An article in the January issue describedin general the principles of magnetic re-cording, and provided specific details onaudio recording. This article provides in-formation on recording of video, withdetail on each of the popular consumervideo formats: VHS, Beta and 8 -mm.

Video recordingThe writing speed for video recording

must be far greater than that for audio. Torecord the higher frequencies using thesame tape velocity that is used for audiowould produce far too short a recordedwavelength. For one thing, it would beimpossible to manufacture tape heads

with a gap small enough.Moreover, there is a problem because

of the broad frequency range needed:30Hz to 4.5MHz, or about 18 octaves. Arecording across this number of octaveswould result in a recorded dynamic rangeof 110dB, far too much to equalize.

Frequency translationThe first thing that must be done to

record video is to translate all frequenciesupward. If all video frequencies aremoved upward by 4MHz, this would givea band for the video frequencies of ap-proximately 4MHz to 8MHz. This wouldbe only one octave.

Since the frequencies must be movedup, it was decided to record the video asan FM signal. The video is not recordeddirectly, but modulates an FM carrier.Using this method helps to prevent ampli-tude variations in the record/playbackprocess from degrading the video.

Another problem is achieving the writ-ing speed required to increase the record-ed wavelength to manageable levels.Longitudinal recording, such as used foraudio, is not feasible; it would consumetape too fast. For example, the writingspeed for the present VHS format is ap-proximately 6m/sec, and for Beta it is ap-

Ritchie is an electronics instructor at Kentucky Tech,Hazard Campus.

Figure 1. The video heads are arranged in thisfashion on the quad scanner cylinder. Tapemotion is perpendicular to the plane of thecylinder.

proximately 7m/sec. All video machines,therefore, provide the high writing speedby "scanning" the tape (moving the headspast the tape) at high speed. The tapemoves at all only to present a new surfacefor this process

Recording the audioOn most VCRs the audio is not record-

ed along with the video, but uses separateaudio heads and conventional audio cir-cuits. A narrow strip of the tape is usedfor the audio tracks. Some newer consum-er machines, however, do place the audioon an FM carrier also and place the audioheads alongside the video heads to scanthe tape. Hi-Fi recordings with excellentquality can be produced this way. Our dis-cussion, for now, will be centered on re-cording and playback of video signal.

The technology

The technical sophistication required

for the magnetic recording and playbackof a video signal, particularly a color sig-nal, is immense.

It is little more than a decade that colorvideo recorders have been available forthe consumer, at least at a reasonable priceand performance. The actual principleshave changed little with time. Mainly thequality and manufacturing improvementshave created improvements in the perfor-mance of these machines.

All video tape recorders, from the mostadvanced professional models to the bot-tom -line consumer models have somethings in common:

A rotating "scanner" to move theheads past the tape to obtain a high writ-ing speed.

Servo control to put the heads in theexact position required as they scan thetape. To do this either the scanner motor,capstan motor, or both can be servo con-trolled. To obtain high enough quality forcolor pictures, usually both must be.

An FM modulator (record) and an FMdemodulator (playback) for the video.

A conventional audio system usingspace on the same tape.

A system to record a "control track"longitudinally (like the audio) to use as areference in positioning the scanner at thecorrect place at all times.

Professional video recordingThe highest quality video recorder,

used for TV broadcasting, is the Quadru-plex, or "quad" video recorder. It uses

Figure 2. The information is recorded in this scheme in the quad videotape format.


two-inch video tape (reel-to-reel in most)and a scanner with four heads, as indi-cated in Figure 1.

The scanner rotates at 14,400RPM anduses a vacuum to form the tape into abowed shape around it. Because 14,400 -RPM is 240 revolutions per second, thescanner rotates 4 times per field. Thismeans there are 16 passes of a video headto record one field.

The tape speeds used are 71/2 inches persecond and 15 inches per second, selec-table. There are two versions, dependingon the frequency of the FM carrier used:high band and low band. The recordingformat, the manner in which the varioussignals are placed on the tape, is shownin Figure 2.

Helical scanA simpler, less expensive way of scan-

ning the tape is to use a "helical scan." Allmodem consumer VCRs use this meth-od. Improvements have been made so thatmany professional recorders also use it.

In this method, the video head describesa helix as it rotates, which creates a record-ed track that is a series of diagonal stripesacross the tape. To accomplish this usingone head, the tape would have to bewrapped entirely around the scanner. Inpractical VCRs, the tape is wrapped 180degrees and two video heads on oppositesides of the cylinder are alternatelyswitched on, to insure head to tape con-tact at all times. One diagonally recordedtrack can contain a complete field.

Two earlier methods that were used toprovide a 360 degree wrap of the tape formachines using a single video head werethe alpha wrap and the full omega wrap.These systems were so named because thepattern of wrapping of the tape resembledthe respective letter in the Greek alpha-bet. The alpha wrap looked like the Greekletter a and the omega wrap looked likethe Greek letter U.

The 360 degree wrap had an inherentproblem: it was difficult to insure that thesingle head stayed in contact with the tapeat all times. It also made threading the tapedifficult. All modern VCRs use a switch-ing system with two video heads. Tapewrap is for a little more than 180 degrees.This insures that one head, at least, is al-ways in contact with the tape.

One of the earliest methods, used withreel-to-reel type recorders was the half -omega wrap. Modern VCRs use a thread -

TAPE

\4%

HEADCYLINDER

"ALPHA WRAP'

HEADCYLINDER

"FULL OMEGA WRAP

TAPE

"HALF -OMEGA' WRAP

Figure 3. The scanner In VCRs that employ "alpha" wrap and the full "omega: wrap, each socalled because the arrangement of the tape resembles the respective Greek letter, uses onlya single video head. All modern VCRs use the "half -omega" wrap scheme, which requires twovideo heads spaced 180 degrees apart on the scanner.

ing method that is similar to the half -ome-ga wrap. Figure 3 shows roughly how thetape was wrapped, or threaded, around thevideo heads for these machines.

To form the helix, the tape has to crossthe scanner at an angle. This can be doneone of two ways. Earlier, reel-to-reel ma-chines tilted the tape path by mounting

one reel higher than the other. Usually thesupply reel was mounted above the take-up reel so that the tape had to move down-ward as it crossed the head. This formedthe helical tracks. The actual tracks on astraight piece of tape are long lines slant-ed at an angle, and these machines weresometimes called "slant track" machines.

MAKING THE HELIX BY TILTING THE TAPE PATH

VIDEO HEADCYLINDER

SUPPLY REEL

-111111111111111-11

TAKE -LIP REEL

MAKING THE HELIX BY TILTING THE HEAD CYLINDER

VIDEO HEADCYLINDER

SUPPLY REEL

imm

TAPE

RECORD VIDEO "TRACKS"

TAKE-UP REEL

Figure 4. One of two methods can be used to create the helical scan pattern of the videosignal on the video tape: tilt the tape path or tilt the head cylinder. Modern VCRs tilt the headcylinder because this method can use a smaller, less expensive, cassette. A general idea ofthe physical arrangement of the video tracks on the tape is shown at the bottom of the figure.


Modem VCRs do not use this methodof producing the slant tracks because itwould make the cassette larger and moreexpensive. Instead, the head is tilted. Thisproduces the slant video tracks on the tapeas the head scans the tape moving straightacross from supply to take-up reel. Figure4 illustrates these concepts and the shapeof the recorded video tracks that result.

Most modem VCRs use one of the twobasic formats; Beta and VHS (VHSstands for "Video Home System," or"Vertical Helical Scan," depending onwho is talking). They are similar, butenough differences exist to make themincompatible with each other. Table 1shows the tape formats for Beta and VHS.

Note that the formats are similar, andboth formats use 1/2 inch tape, but thethreading method and hence, the cassettecases, are different. They are not similarenough, however, to allow a Beta ma-chine to play a VHS recording even if youremoved the tape and put it in the correcttype of cassette.

The Beta format is actually somewhatbetter in picture quality than the VHS for-mat because of the longer track length.The VHS format, however, has becomemuch more popular because it allows fora longer recording time.

In both VHS and Beta machines, thescanner is most often referred to as thecylinder. It may also be referred to, insome service manuals, as the "upper cyl-inder," the "lower cylinder" being the mo-tor that rotates the scanner. In older ma-chines it was called the "drum" and issometimes called this in newer machines.

U-MaticAnother type of cassette recorder that

came into common use as a commercialvideo cassette recorder was the U-Maticformat. The U-Matic machines are stillused in industry and are popular at TVbroadcast facilities. It is a format that useslarger tape (3/4 -inch) and a larger car-tridge. The scanner is much larger pro-ducing longer tracks, and a faster tapespeed is used so better, more stable pic-tures are possible. This machine was theforerunner of the Beta machine and, me-chanically, the Beta machine is a minia-turized version of it.

As for consumer VCRs (Beta andVHS), FM is still used to record the lumi-nance video. In the Quad recorder, thecomplete video (Y and C signals) mod -

GUARDBANDS

0.2mm WIDE

0.3mmGUARD BAND

GUARD BANDS0.15mm WIDE

1 11 I I 1 LI 111 III 11 1 1 II LI I 1 11 I 1 I

BETA RECORDING FORMAT

AUDIO TRACK1.05mm WIDE

VIDEO TRACKS40-- 117mm LONGABOUT 5 SLOPE

I 1111.'11[111 (iiiVHS RECORDING FORMAT

CONTROL TRACK0 6mm WIDE

41111-- L

AUDIO TRACK0.35mm WIDE

VIDEO TRACKSOn- 97.3mm LONG

ABOUT 6 SLOPE

1111/C. CONTROL TRACK0.75mm WIDE

Figure 5. The recording scheme for VHS is similar to that of Beta, but the threading and hencethe cassettes are different. Even if you put a VHS tape in a Beta cassette, or vice versa,however, it would not play.

ulates the FM carrier. This is possible withthe Quad machine because of its quality.

The head in a Quad machine alone maycost several thousand dollars and thecomplete recorder almost $100,000 dol-lars. It is still not feasible, however, to re-cord the color signal along with the lumi-nance for the consumer VCR.

Recording chroma and lumaTo see why the color (chroma) and lum-

inance (luma) can't be used together tomodulate the FM carrier in consumerVCRs, consider these facts. The head cyl-inder, only two to three inches in diame-ter, scans the tape producing tracks thatare roughly five inches long. A singletrack contains one complete field of vid-eo. Thus each horizontal line of video isrecorded on a length of tape that is 5/262.5of an inch, or about 0.02 inches long.

Remember now about head gap width,writing speed, and recorded wavelength.

If the signal has color on it, a 3.58MHzsignal produces about 227 cycles per hor-izontal line, so each cycle of the color oc-cupies about 0.02/227 inches, or about 8.8millionths of an inch. There will be vasterrors if the heads are only millionths ofan inch in the wrong place at any time. Achange in phase of only a few degrees

from one rotation of the head to the nextis intolerable-color oscillators in TVsets could not follow it.

Overcoming the problemsBefore video can be recorded suitably,

there are many problems to overcome:

Variations in tape tension Tape stretch Dropouts (oxide bad or missing) Head to tape contact at the high writ-

ing speed Variations in capstan speed and rota-

tion speed of cylinder Providing electrical contact to rotat-

ing heads Crosstalk between adjacent tracks Switching between the two video

heads at the correct time.

The tension regulatorTo correct for variations in tape tension,

a tension regulator is used. This is a me-chanical device that will be the first com-ponent in the tape path. It usually is ametal band with a felt strip on the insidethat provides variable "braking" for thesupply reel. If the tape has too much ten-sion, a loop in the tape will tighten, pull-ing on the band to release it slightly and


allow the supply reel to turn easier, low-ering the tension. If there's too little tapetension, the tension regulator compen-sates to increase it.

The dropout compensatorTo make dropouts less objectionable,

all VCR's have a dropout compensator,or DOC. This is a circuit that delays thevideo for 63.5µsec, and thus always hasthe previous horizontal line output fromit. The circuit senses if the video signaldisappears (there is a dropout) and, if so,switches in the video from the previousline. The eye cannot detect momentarydropouts of only one or two lines becauseadjacent lines are very similar.

Head -to -tape contactAs for head -to -tape contact, the heads

are made to protrude very slightly into thetape, that is, they project slightly from thesurface of the cylinder they are mountedon. The biggest problem here is tape con-tact with the cylinder itself, which mustrotate at 1800 RPM. Actual contact withthe cylinder would destroy tape and cylin-der in a short time. Lubricants cannot beused, as they would destroy the tape.

What is done is to put fine grooves inthe cylinder. Before the tape is pulled tothe cylinder in the thread operation, thecylinder is started to rotate. This createsan air cushion because the grooves andthe tape actually do not touch the cylin-der, but ride just above its surface on theair cushion. If anything were to fill upthese grooves, even a tiny amount of oil,the cylinder and tape would seize, possi-bly destroying the heads and the tape.

The use of an FM carrier for the lumi-nance video also helps to minimize vari-ations in head to tape contact because theFM demodulator is not sensitive to ampli-tude variations.

Getting the signal to and fromthe heads

To couple the video signal to and fromthe rotating heads, older machines usedslip rings and brushes. These gave manyproblems because of dirty, bent or worncontacts. All VCRs now use rotary trans-formers to couple the energy to and fromthe heads. One circular winding is in therotating upper cylinder, the other is in thestationary lower cylinder. The circularwindings are precision wound with pri-

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3.437867MHZ

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VHS FREQUENCY SPECTRUM

...%4.407867MHZ

4.4MHZPEAK WHITE

LUMINANCE FM AND SIDEBANDS

I

3.5MHZSYNC TIP

BETA FREQUENCY SPECTRUM

4.8MHZPEAK WHITE

Figure 6. The VHS frequency spectrum is somewhat different from the frequency spec-trum for 3eta.

mary and secondary windings that keep aconstant relative position to each other.

Speed controlTo minimize speed irregularities, the

cylinder and capstan motors are servocontrolled. Switching between the headsis accomplished at the proper time by gen-erating a reference pulse from a pulse gen-erator in the rotating cylinder and com-paring this pulse to the vertical sync pulse.

Still, the heads cannot be positionedaccurately enough to allow the color to bedemodulated and used "as is," even in theexpensive Quad machines.

The phase and frequency variationsthat remain, caused by the small shortterm changes in writing speed, are called"jitter" components of the signal. Thesetiming irregularities are very harmful tothe color signal because this signal is sophase dependent.

All video recorders that use color musthave a type of "velocity compensation"whereby two signals are created with thesame jitter components and heterodynedtogether to produce a stable differencesignal. For broadcast use, a time base cor-rector is used to stabilize the longer termvariations in the signal frequencies.

VHS ''M" WRAP

BETA

VIDEOHEAD

CYLINDER

Figure 7. The tape wrap schemes are different in the VHS and in the Beta VCRs.


Modulation and demodulationVCRs are not capable of recording the

color in the same band of FM frequenciesin which the luminance is recorded. TheFM modulation and demodulation wouldcreate beat interference because 3.58 -MHz is within the band of FM frequen-cies used. Quad machines can do it be-cause their FM carriers are up in the rangeof 8MHz to 12MHz.

The cost would prohibit consumerequipment from using this method. In-stead, the color is moved out of the way.It is moved down in frequency, below theFM luminance frequencies. This used tobe referred to as the "color under" or "het-erodyne" color system. This enables thelimited bandwidth of present VCRs torecord color separate from the luminance,preventing interference between the two.It does, however, limit the bandwidth ofthe color that is recorded. The actual fre-quencies that are used for the two systemsare shown in Figure 6.

The two sets of frequencies given forthe VHS luminance signal have to do witha method of preventing crosstalk and willbe discussed later.

Another Beta version called "Superbeta" centers the FM luminance at 5.17 -MHz for greater picture detail.

Mechanical differences

In addition to the electrical differences,there are mechanical differences betweenVHS and Beta machines. To get the min-imum 180 -degree wrap around the headcylinder, the tape must be pulled from thecartridge and "threaded." These ma-chines use different methods, as shown inFigure 7.

Other differences, in comparing Beta toVHS are:

Beta uses a smaller cassette. This isan advantage in that it is more compact,but it holds a shorter spool of tape so thereis less record time.

The thread operation occurs as soonas the cassette is inserted in the Beta ma-chine, and stays threaded at all timeswhen the cassette is in the machine. Thisgives better control over tape movementand allows faster operation betweenmodes, such as from stop mode to playmode. It is, however, a little more dam-aging to the tape during FF and REWoperations. (A few "instant play" VHSmachines are now doing this also.)

Table 1. Beta and VHS tape parameters

FORMAT SPEED TRACK TRACKWIDTH LENGTH

Beta 1 1.6 in/sec(40 mm/sec) 58 microns 117 mmBeta 2 0.8 in/sec(20 mm/sec) 29.2 microns 117 mmBeta 3 0.53 in/sec(13.3 mm/sec) 19.5 microns 117 mmVHS-SP 1-5/16 in/sec(33.35 mm/sec) 58 microns 97.3 mmVHS-LP 21/32 in/sec(16.67 mm/sec) 38.5 microns 97.3 mmVHS-EP 7/16 in/sec(11.12 mm/sec) 19.2 microns 97.3 mm

Beta video tracks are a little longer,as mentioned earlier. This allows for a lit-tle wider FM bandwidth for the lumi-nance, and therefore resolution that is alittle better.

Improved formatsRecently, new formats for both VHS

and Beta have been developed that pro-vide better picture detail (better resolu-tion). As a comparison, broadcast TV sig-nals have a resolution of about 330 lines.VHS VCRs use a chrominance signal atapproximately 629KHz that trails off atabout 1.13MHz. The luminance extendsfrom there, up to about 4MHz, giving abandwidth of about 2.9MHz. This pro-duces about 250 lines of resolution.

Beta resolution is slightly better, atabout 260 lines of resolution. The newerSuper beta has a bandwidth of about3.2MHz. that gives a resolution of justunder 300 lines.

As mentioned, recent advances havecreated new formats that are superior inresolution, but unfortunately incompati-ble with the old formats. The two new for-mats are Super VHS and Extended Defi-nition BETA (ED BETA).

Actually, there are three basic formats,but the third, 8 -mm, is not yet in commonuse for VCRs, although it may be in thenear future.

The newer Super VHS has a color sig-nal identical to the signal used in the oldsystem. The difference is in the FM lumi-nance. It uses a higher band of frequen-cies, allowing a wider bandwidth and thusbetter picture detail.

The sync tip and peak white frequen-cies for Super VHS are 5.4MHz and7MHz. This produces a resolution capa-bility that exceeds 400 lines. This is much

better resolution than a broadcast TV sig-nal, and better than most TV receivers are

capable of displaying. To see the picturewith full quality requires the use of a colormonitor with a special S -VHS input jack.The S -VHS connector has separate cablesfor the luminance video, color signal, andthe audio channels. This provides muchbetter quality because the Y and C signalsare separate and the high frequency lumi-nance cannot beat with the C signal andproduce beat interference. These moni-tors are capable of displaying typically400 to 500 lines of resolution.

Compatibility considerationsTo provide compatibility, S -VHS

VCR's have built in record and playbackcircuits for standard VHS. For recording,a switch can select the desired format. Forplayback, the circuits automatically de-tect whether the signal is VHS or S -VHS.The use of S -VHS requires special high-er quality tape that is capable of record-ing the S -VHS signal. The signal-to-noiseratio for the luminance in standard VHSis a little better than 40dB, and can be afew dB higher for S -VHS. The color sig-nal is, however, improved only slightly.It is recorded exactly the same and whatimprovement is noted is because of thehigher quality tape.

The newer ED Beta provides muchmore resolution than even S -VHS; over500 lines. As with S -VHS, the color sig-nal is recorded the same and the lumi-nance FM band is much higher. The synctip and peak white frequencies for EDBeta are 6.8MHz and 8.6MHz. Moreover,ED Beta uses a special tape, that is evenmore demanding than S -VHS, that usesextremely fine metal particles instead ofoxide particles.

The favoriteAt present, the clear favorite standard

is VHS. The main reason that VHS be -


came the favorite was the decision to usea little larger cassette and thus more tape,to provide a longer play/record time. It isdifficult to predict what the future will be,but S -VHS will probably become themost popular standard in the next fewyears. Although S -VHS is not the superi-or format for picture quality, it still pro-vides the longest play/record time and S -VHS VCR's are being built that will playstandard VHS recordings. This insuresthat the consumer's tape library will stillbe usable with the purchase of the S -VHSvideo cassette recorder.

The 8 -mm formatAs mentioned earlier, there is a third

basic tape format, but it is not as popularand is used primarily (at present) for cam-corders. This is the 8 -mm format. Theoriginal 8 -mm format provides better pic-ture quality than either VHS or Beta,including the color signal. The 8 -mm for-mat was developed to provide a muchsmaller tape cassette for use in camcord-ers. 8 -mm tape is about one-third of aninch wide, only slightly larger than reel-to-reel and 8 -track audio tape, but of amuch higher quality, using metal particleslike the ED Beta tape.

The 8 -mm cassette is not much largerthan the standard audio cassette. The for-mat uses a color signal at 743KHz, and aluminance signal with sync tip and whitepeak frequencies of 4.2MHz and 5.4 -MHz. Picture resolution is between thatof VHS and S -VHS.

Recently, a new 8 -mm format calledHi -Band 8 -mm, or "Hi -8," was devel-oped. The color is the same and improve-ment was provided by moving the lumi-nance FM frequencies up, as it was for theothers. For Hi -Band 8 -mm, the sync tipand peak white frequencies are 5.7MHzand 7.7MHz and provides roughly thesame resolution as ED Beta.

8 -mm does not use an audio track. In-stead, all 8 -mm machines use the hi-fisound system in which the sound modu-lates an FM carrier and is recorded byheads mounted on the rotating head cylin-der. This FM carrier is located in the gapbetween the chroma frequencies and theluminance FM frequencies. This appliesto the hi-fi machines in the other formatsas well. This provides for sound that hasas wide a frequency response and almostas good a dynamic range as CD players.

It can be argued that the 8 -mm format

is the best of all, but its popularity at pre-sent is limited. It could be that the choiceof the name is part of its problem. Therewas an 8 -mm film format that was thestandard for home movies before the ad-vent of VCRs and camcorders, and someof the public may be confusing the two,believing the 8 -mm camcorder to be a

film camera. Of course, the lack of pre-recorded tapes in the 8 -mm tape format isa definite handicap.

Coming attractions

A future article will cover some of thecircuits in VHS and Beta VCRs and de-scribe in more detail how they work.

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Coping with hard disk problemsPart IIBy Stephen J. Bigelow

Part I of this three-part article, publishedin the January issue of ES&T, describedthe various parts of a hard drive system,and detailed the similarities and differ-ences among the different types of harddisk drives. This part lists some of thehard drive hardware error messages thata technician may encounter and suggestsa course of action to take when they areencountered.

Pre -service checkoutWhen you encounter a hard drive error

message, take a minute to consider thefollowing installation points. First, makesure that the drive controller board (andevery board in the PC) is seated firmlyand evenly into its expansion slot. Alsomake a careful inspection of the drive'spower and signal cable(s) to ensure thatthey are intact and inserted properly intotheir corresponding connectors.

Refer to the documentation for thedrive and controller board. Inspect anyjumpers or DIP switches that are used toset address settings, drive numbers, inter-rupt lines, or DMA configurations. Anincorrect selection on the drive or con-troller can render the drive inoperative.

Next, measure the power supply outputserving the drive. Most drives use a 4 -pinmate-n-lok connector for power. The twomiddle pins are ground (or return) lines.One side of the connector supplies+12Vdc, and the opposite side of the con-nector supplies +5Vdc. If one or both ofthese voltages is low or absent, the drivemay function erratically (or not at all).You may need to either troubleshoot thepower supply or upgrade it to a higher -capacity supply.

When you are confident that the driveand controller are configured properly, in-serted correctly, and have adequate pow-er, you can go on to specific troubleshoot-ing steps.

Bigelow is a technical author and computer consultant atDynamic Learning Systems in Marlboro, MA.

Figure 1. Hard disk drives have long been a focal point of PC technology.

Hardware initializationtroubleshooting

Initialization problems are surprising-ly common. They can occur when thedrive or controller fails, but initializationproblems can also occur when a new driveis installed improperly, or is incompati-ble with the existing system setup.

Following are a number of symptoms,along with some recommended correc-tive actions.

The screen goes blank when thesystem is powered up

This is a problem encountered duringnew drive installation. If the display doesnot appear after power up (you should ini-tially see a BIOS ROM copyright noticeand the memory test), there is likely ahardware conflict between the drive con-troller board and the system.

Make a quick check of the monitor tobe sure its power cord or video cable hasnot worked loose during the hard drive in-stallation process. Power down the com-puter and remove the new controllerboard. If the problem disappears, checkthe I/O address, DMA, and IRQ settingson the drive controller board.

However, if the controller board set-tings check properly, reinstall the driveand controller board, power up the sys-tem again, and measure each output fromthe power supply. If one or more supplyoutputs becomes low or absent, the sup-ply may be undersized, or there may be aserious short circuit somewhere in thecontroller or drive. Try a new or similarcontroller. If the problem persists, try alarger power supply, or remove otherexpansion boards from the system toreduce loading on the supply.

The IDE drive fails to spin -upproperly after power is applied

This problem usually occurs when anew drive or controller board is installedor upgraded. One end of a signal cablebetween the drive and controller board isprobably reversed. Check the signal cablealignments and ensure that both ends ofthe cable(s) are inserted properly.

In an AT system, the drive lightstays on continuously

A continuous LED indication is notnecessarily a problem as long as the driveseems to be operating properly. Refer to


the documentation for the controllerboard-there may be a jumper availableto switch the LED display between a"latched" mode (the LED is always on)and an "activity" mode (the LED is onlyon during drive access). If such a jumperexists on the drive, set the jumper to the"activity" mode.

If the drive does not operate, powerdown the computer and check the signalcable(s) between the drive and controllerboard. One end of a signal cable is prob-ably inserted upside-down. Reinstall thesignal cable(s) correctly and retest.

A "No Fixed Disk Present" errormessage is displayed on the monitorThis kind of problem can occur during

installation, or at any point in the PC'sworking life. If you are installing/upgrad-ing a drive system (or installing a newboard in the system), there may be anaddress or IRQ conflict with other boardsin the system-a common difficulty.Since it is very difficult to know theaddress and IRQ layout of each board inthe system, your best strategy is to removeall expansion boards in the system otherthan the drive controller.

Try the system again. If the drive oper-ates, there is a conflict with one of theboards you removed. Replace one boardat a time. When the problem returns, youknow that the board you just installed isthe problem. It is then your choicewhether to change the settings of thedrive controller, or of the "other" board.

It is usually a better idea to adjust thecontroller board because you probablyhave the documentation for it right onhand. It would also be a serious hassle tofind and alter the customer's existing util-ity configurations after making changesto "other" boards. Make the new con-troller fit the old system-not vice versa.

Refer to the system's setup routine andensure that the correct drive type anddrive parameters are entered in the CMOSsetup screen. One or more faulty para-meters can disable the drive. You mayhave to check the drive's parameters(cylinders, heads, sectors, landing zone,and write pre -compensation) against pa-rameter data from the drive manufacturer.

If you cannot find a prefabricated drive"type" with the appropriate parameters,you can usually enter the proper parame-ters manually as a "custom" drive type. IfCMOS RAM has failed, replace the back-up battery and re-enter each setting. Be

platters

spindle(motor mounted

underneath)

headactuator

ad/write circuitry(interface board

ounted underneath)

Figure 2.. In last month's issue we mentioned tne 4ive critical elements of a current hard driveassembly that are shown here.

sure to write down each setting and tapethe notes inside the PC cover.

Check for any loose power and signalcables. In a multi -drive system, make surethat any drive jumpers or DIP switchesfor each drive are configured properly formulti -drive operation (master/slave set-tings). If any terminator resistors areneeded, make sure that the terminators areinstalled in the correct locations. You maytry low-level formatting the drive again.

The system fails to recognize thepresence of the drive

The computer may flag this as a "hard -disk error" or "hard -disk controller fail-ure" during system initialization. Beginyour inspection by checking the drive'ssignal cable orientation. When installingor upgrading a drive, be sure that the redlead of the ribbon cable (pin 1) is orient-ed toward connector pin 1 at both ends. ifthe cable is reversed at either side, thecontroller board will not recognize thepresence of a drive.

Double check any jumpers used to con-figure the drive or drive controller board.Drive configuration jumper settings areeven more critical when there is more thanone drive in the system. Each drive musthave unique identifying settings, other-wise a communication conflict will occurthat can temporarily disable all the drives.

If the drive still fails to operate after in-stallation or upgrade, there may be an ad-dress or IRQ conflict with other boards inthe system-a common difficulty. Sinceit is very difficult to know the address andIRQ layout of each board in the system,your best strategy is to remove all expan-

sion boards in the system other than thedrive controller.

Try the system again. If the drive oper-ates, there is a conflict with one of theboards you removed. Replace one boardat a time until the conflict resurfaces-the board you reinstalled when the con-flict returned is the source of the problem.It is then your choice whether to changethe settings of the drive controller, or ofthe "other" board.

It is often a better idea to adjust the con-troller board because you probably havethe documentation for it right on hand. Itwould also be a serious hassle to find andalter your customer's existing utility con-figurations after making changes to "oth-er" boards. Make the new controller fitthe old system-not vice versa.

Next, be sure the drive actually spinsup when power is turned on. You shouldbe able to hear this, but some hard drivesare extremely quiet. If the drive fails tospin up, check the power supplied throughthe 4 -pin mate-n-lok connector as de-scribed in the "Pre -Service Checkout"section. If one or more supply voltages islow or absent, the drive will certainly notfunction. Troubleshoot or replace thepower supply.

Double-check the controller board tobe sure that it is compatible with the driveyou are using (not a problem with IDEdrives). While instances of incompatibil-ity between drives and controllers thatshare the same signal interface is rare, itmay happen under some unusual circum-stances. Remember, not all SCSI devicesare compatible with every host controller.

One test of controller incompatibility


for ST506/412 and ESDI drives is the sys-tem speed test; older PC expansion boardsexpected the ISA bus to operate at about8MHz, but today's powerful systems op-erate so fast that the controller board can'tkeep up.

If the computer is in a high-speed (orturbo) mode, take the system out of theturbo mode and re -try the drive. If thedrive operates when a lower bus speed isused, a more sophisticated controllershould probably be used.

Refer to the system's setup routine andensure that the correct drive type anddrive parameters are entered in the CMOSsetup screen. One or more faulty para-meters can disable the drive. You mayhave to check the drive's parameters (cyl-inders, heads, sectors, landing zone, andwrite pre- compensation) against para-meter data from the drive manufacturer.If you can't find a prefabricated drive"type" with the appropriate parameters,you can usually enter the proper parame-ters manually as a "Custom" drive type.

A "Drive not Ready" error messageis displayed on the monitor

This problem is typically encounteredduring installations and upgrades. Thesystem does not recognize the drive. Be-gin your inspection by checking the sig-nal cable between the controller and drive.One end of the cable may be reversed.

Inspect outputs from the power supplynext. Power is typically through a 4 -pinmate-n-lok connector. The middle twopins are ground. One end provides +5Vdcand the other end provides +12Vdc.

If one or both of the supply voltages islow or absent, the supply may be under-sized for the power load demanded by thesystem. You could try a larger supply. Ifpower is adequate, make sure that thedrive spins up.

Inspect any jumpers or DIP switchesand make sure the drive is set properly forthe type of controller being used. If thedrive is not configured properly, the sys-tem will not recognize the drive. Thedrive may be low-level formatted im-properly. Check the low-level drive para-meters used in low-level formatting. Ifany of the parameters are incorrect, cor-rect the parameters and try reformattingthe drive again.

A drive formatted by a dealer doesnot operate after installation

Start by checking the controller and

cable installation. Also check the systemCMOS to be sure that the proper parame-ters are entered for the drive being used.This is especially important when usingan IDE drive in "translation mode."

Find out if the DOS version used to par-tition and high-level format the drive iscompatible with the system. A hard drivewith an incompatible format or partitiontable will not function in the system.

Make sure you are using the same drivecontroller board used by the dealer whoprepared the drive. Also check that youare using the same type of cables. It maybe necessary to re -partition the hard drivefrom scratch to ensure compatibility.

The IDE spins up when powered,then rapidly down again

If the drive is not communicating prop-erly with its host system, try a new signalcable between the drive and its controllerboard. If a new cable fails to restore thedrive, there may be an incompatibility be-tween the drive and the system's BIOS. Toconfirm this, try the drive and "controllerboard" on another system using a newerBIOS, or a BIOS from a different manu-facturer. If the problem does not occur onanother machine, you may need to upgradethe BIOS ROM(s) on the original system.

A "Sector not found" error messageis displayed on the monitor

This problem usually occurs after thedrive has been in operation for quite sometime. Inspect the signal cable(s) betweenthe drive and controller. Try using newcables. If the cables are intact, there maybe a media fault on the drive-the driveitself may be defective.

If you had just replaced the drive con-troller with another model, there may bean incompatibility in the low-level for-mat. Try another controller board of thesame model.

If the problem persists (or an appropri-ate controller board is not available), trybacking up as much of the drive as pos-sible, and re -work the drive (try to per-form a new low-level format, repartitionthe drive, and reformat the drive).

A "1780 or 1781 ERROR"is displayed on the monitor

The classic 1780 error code indicates a"Hard Disk 0 Failure," while the 1781error code marks a "Hard Disk 1 Failure."The term Failure is used to suggest that ahardware fault has occurred. In a new

installation or upgrade, make sure that thecontroller is compatible with the drive.When this fault occurs in an establishedsystem, your best course is simply toreplace the hard drive. If the error codedisappears when another hard drive isused, the original drive can be returnedfor repair or replacement.

A "1790 or 1791 ERROR"is displayed on the monitor

The classic 1790 error code indicates a"Hard Disk 0 Error," while the 1791 errorcode marks a "Hard Disk 1 Error." Theterm Error is used to suggest that a logi-cal or operational fault has occurred (asopposed to a hardware failure). In manycases, this error is generated when a driveis brand new and needs to be low-levelformatted, partitioned, and DOS formatted.

Because 1790 -type errors are logical innature, a signal interruption may be oc-curring between the drive and controller.If the drive has already been prepared bya dealer, try a new signal cable betweenthe controller and drive before you con-sider re -partitioning and reformatting.

A "1701 ERROR" is displayedon the monitor

The 1701 error code indicates a harddrive POST (power -on self test) error: thedrive did not pass its POST test. Checkthe drive setup data entered in the systemCMOS. Also check that the drive's signaland power cables are connected proper-ly. If you are installing a hard drive in anolder PC/XT system, you should performa low-level format on the drive (if that isappropriate).

The system reports random data,seek, or format errors

Random errors rarely indicate a per-manent problem, but identifying theproblem source can be a time-consumingtask. Start by checking the drive power asdescribed in the "Pre- Service Checkout."Marginal power supply levels (especial-ly in fully -loaded systems) can result instrange, random faults. Electrical noise inthe system can also interfere with normaldrive operation.

Try re-routing the signal cable awayfrom the power supply and other expansion boards. You may also try placing ex-pansion boards in other slots which arefarther away from the drive signal cable.

(Continued on page 41)


Hard Disk Problems(from page 28)

Electrical noise can also affect the drivecontroller board. Install the controllerboard away from the power supply, andtry to keep it away from the video adapterboard if that's possible.

There may be a problem with the sys-tem speed. Although most ISA bus sys-tems are designed to run at 8MHz, somenew machines run so fast that communi-cations between the system and driveadapter is marginal. Try taking the PC outof its "turbo" mode. If the problem dis-appears, replace the drive controllerboard with a newer, faster board.

Try the drive and controller in anothersystem. If the drive and controller workin another system, there is probably ex-cessive noise or a grounding problem inthe original system. Reinstall the driveand controller in the original system andremove all extra expansion boards (ex-cept the video adapter).

If the problem goes away, replace oneboard at a time and retest the system untilthe problem returns. The last board youinserted when the problem returned isprobably the culprit. If the problem per-sists, there may be a ground problem onthe motherboard. Try replacing it.

There may be a marginal area on thedrive. Back up as much of the hard driveas possible and use a third -party harddrive utility such as PC Tools or NortonUtilities to perform a thorough scan of thehard drive media. Use such tools to markout any media errors, then reformat.

There are problems when installinga new hard drive using a second

disk controllerThe system may also not boot after a

second controller is installed. Systemconflicts will almost invariably resultwhen two drive controllers are present inthe system. Make sure that the new con-troller is correct for the drive beinginstalled. The controller should also haveits own on -board BIOS that can be usedin a system without having to specify aCMOS drive type.

Check the I/O address of each con-troller BIOS. Make sure that the BIOS I/Oaddress of each controller is set differ-ently. If addresses overlap, a hardwareconflict will result. Since many drive con-trollers also offer floppy drive controllers,make sure that all unused floppy drivecontroller circuits are disabled.

A "Bad or Missing CommandInterpreter" error message

is displayedThis is a typical error that appears when

a drive is formatted in one DOS versionbut loaded with another. Compatibilityproblems occur when you mix DOS ver-sions. Make sure that the drive is format-ted with the DOS version you intend touse, and that the /S option is used withFORMAT in order to transfer the propersystem files to the boot device.

If this is a new problem on an existingsystem, you should strongly suspect thepresence of a computer virus. Use a cleanvirus checking disk to examine the harddrive and eliminate the virus if possible(once checking is complete, discard theanti -virus work disk). You may need torecopy COMMAND.COM to the harddrive. If you need to reformat the driveagain, back up as much of the drive aspossible before proceeding.

An "Error reading drive C:" errormessage is displayed

Read errors in a hard drive typicallyindicate problems with the disk media,but it is always worthwhile to check thedrive's signal and power cables first to en-sure that each is secure. If faulty cablingis not the problem, use some good anti-virus software and scan the drive for acomputer virus. Remove any infectedfiles. If a computer virus is detected, youshould also check every floppy disk thatyou have available since any disks usedin an infected system may also be infect-ed (and can re -infect the hard drive orother PCs).

Use a commercial PC utility such as PCTools or Norton Utilities to scan the harddrive for defects. If defects are detected,try mapping out such defects as dictatedby the particular utilities. If the problempersists, it may indicate failing sector andtrack ID information. This may also be afactor if the drive's orientation haschanged (i.e. you re -mount the drive ver-tically where before it was horizontal).

Back up as much of the drive as possi-ble, and perform a new low-level formatof the drive (if possible). Establish a newDOS partition, and run a new DOS for-mat. Restore the backup and recreate anyfiles that were lost due to original error.

A "Track 0 not found" error messageis displayed

Start by checking the interconnectingcables between the drive and controller.

Try a new cable. Also check to be surethat you are using DOS 3.3 or later (if youdo upgrade, move to MS-DOS 6.2 or lat-er). If cabling and DOS versions are right,the problem is likely on the drive itself.

A fault on track 00 can disable the entiredrive since track 00 contains the drive'sFile Allocation Table (FAT). Back up asmuch of the drive as you can (this may beimpossible with a track 00 problem) andperform a low-level format of the drive(if possible). You will then need to repar-tition the drive and perform a new DOSformat. If this procedure fails to restoretrack 00, you will have to replace the harddrive outright.

Software diagnostics indicate a longeraverage access time than is specified

The average access time is the averageamount of time needed for a drive to reachthe track and sector where a needed filebegins. Verify the specifications for theparticular drive. Keep in mind that dif-ferent software packages measure accesstime differently. Make sure that the diag-nostic subtracts system overhead pro-cessing from the access time calculation.Try one or two other diagnostics to con-firm the measurement.

If different software tools confirm themeasurement, test several identicaldrives. If all drives measure the sameway and work properly, check with thedrive manufacturer for a technical expla-nation. If only the suspect drive measuresincorrectly, consider replacing thedrive-or at least warn the user to per-form a full drive backup.

Software diagnostics indicate a slowerdata transfer rate than specified

Verify the specifications for the partic-ular drive and controller. Keep in mindthat different software packages measureaccess time differently. Try several dif-ferent software diagnostics to confirm themeasurements.

If the drive is an IDE type, make surethat the original user did not perform alow-level format-this may remove headand cylinder skewing optimization andresult in a degradation of data transfer. Ifno low-level formatting was performed,the drive may be failing. Either replacethe drive or perform a full drive backup.

Next timeThe next, and final, installment will

describe software -related hard -disk prob-lems and will suggest various ways ofcoping with them.


Electronic tuner theory andtroubleshooting-Part ITheoryBy Steve Babbert

The advent of the electronic tuner fortelevision sets marked a radical departurefrom the existing technology. It eliminat-ed the need for most of the moving partsused in the mechanical tuner. Numerousswitch contacts, shafts and gears, as wellas many of the inductors and capacitors,were replaced with microprocessors,PLLs (phase lock loops), prescalers andvaractor diodes.

The mechanical tuners often developedproblems due to failure of one or moreswitch contacts. Sometimes these prob-lems could be solved by cleaning. Othertimes rebuilding or replacement of thetuner was the only solution. In any event,the problems were usually easy to diag-nose and understand.

When troubleshooting the electronictuner, which bears very little resemblanceto the mechanical tuner, many techniciansfind it difficult to pinpoint the source ofa problem. This article will attempt to de-mystify the electronic tuner and outlinesome basic troubleshooting procedures.But first, let's look at exactly how a typ-ical tuner operates.

Babbert is an independent consumer electronics servicingtechnician.

The purpose of the tunerThe purpose of the tuner is to select a

single radio frequency (RF) channel fromthe many channels that make up the UHFor VHF band, and convert it to an inter-mediate frequency (IF). While the RF fre-quency is different for every channel, theIF frequency is always the same. Usingthis method, all stages of amplificationfollowing the tuner won't need to be re-tuned during channel selection. Conver-sion of RF to IF is made possible by a pro-cess known as heterodyning.

In the heterodyning process, the signalfrom a local oscillator (LO) in the set ismixed with or "beat" against the incom-ing RF signal in a stage known as a mixer(see Figure 1). The actual mixing takesplace in a non-linear device. In a lineardevice such as a resistor, changes in volt-age across the device are accompanied bydirectly proportionate changes in currentthrough the device, so no heterodyningcan take place.

Most semiconductors are non-linear. Inmodern VHF tuners the mixer is often aMOSFET while UHF tuners generallyuse a Schottky Barrier Diode. In the earlydays of radio this stage was often referredto as the "first detector." This term was

supplanted by the commonly used "mix-er" many years ago reserving the use ofthe term "detector" for the stage that ex-tracts the so-called intelligence or base -band audio, video or both from the carri-er after amplification in the IF stages.

Mixer outputThe output of the mixer contains the

sum and the difference of the two inputfrequencies and in some cases the twoinput frequencies as well (this is deter-mined by what type of mixer is used).Mixing 113MHz (the channel 4 LO fre-quency) with 69MHz (the center of thechannel 4 RF frequency) will result in a44MHz and a 182MHz output.

An in depth discussion of the varioustypes of oscillators and mixers is beyondthe scope of this article. Suffice it to saythat after the filtering of any undesiredremnants at the output of the mixer, onlythe IF frequency will remain.

In the NTSC system, the difference fre-quency, which is centered at 44MHz, isused for the IF. The actual frequencies ofthe sound and video carriers are 41.25 -MHz and 45.75MHz respectively.

Any channel in the UHF or VHF bandcan be converted to the IF frequency by

Figure 1: In the heterodyning process, the RF signal is mixed with a signal from a local oscillator in a non-linear device to produce the IF

frequency.


ANTENNA

TUNEDCIRCUIT

f

TUNEDCIRCUIT

/

_L

TUNEDCIRCUIT IF

Figure 2: In the VHF tuner four circuits are tuned simultaneously. These circuits can be tuned mechanically by changing component values, orelectronically by using varactor diodes in conjunction with a variable voltage source.

selection of the appropriate LO frequen-cy. In the most common mechanical VHFtuners (rotary style), when the channel ischanged, a different set of inductors and/or capacitors is switched into the LO cir-cuit. These are frequency determiningcomponents and therefore change the LOfrequency. The UHF tuner generally usesa set of continuously variable capacitorsfor tuning.

The first RF amp, which is often re-ferred to as a preselector since it is aheadof the mixer, is also tuned at its input andoutput by this method to select a channel.The input to the mixer also uses this tun-ing method. The electronic tuner achievesthe same results by varying the dc volt-age on a series of reverse -biased varactordiodes that are used as frequency deter-mining components in the above men-tioned stages (see Figure 2).

The varactor diodeA reverse -biased varactor (variable re-

actance) diode exhibits capacitance thatis inversely proportional to the voltageacross its P -N junction. The greater thereverse bias, the lower the capacitance:hence the higher tuned -circuit resonantfrequency (see Figure 3a). Physically, thechange in capacitance is attributable tochange in the width of the depletion re-gion under varying reverse bias conditions.

In semiconductor diodes, a depletionregion or space -charge layer exists at thejunction of the P and N type semicon-ductor layers. This is a result of mobile

charge carriers drifting from the P layerto the N layer and vice -versa. Under no -bias conditions, this diffusion flow reach-es equilibrium at some point. Since thedepletion region is devoid of charge car-riers it acts as a dielectric (in this case theinsulating material between the twoplates of a capacitor).

The opposing surfaces of the P and N

layers effectively act as the plates of thecapacitance. As the reverse bias is in-creased, the depletion region widens,which reduces the capacitance (capaci-tance is inversely proportional to the dis-tance between the plates). Though manykinds of diodes exhibit this effect, by con-trolling the doping profile at the junctionduring manufacturing, the varactor diode

DEPLETIONIREGION

IN EFFECT7HE

DIELECTRIC

0 0 0 a0 0

00 0

0O 0 0 0P N

P AND N LAYEFSIN EFFECT THE PLATES

Figure 3a: When the reverse bias is increased, the depletion region is widened, effectivelyncreasing the distance between the "plates" hence decreasing the capacitance.


VD,

VARIABLEVOLTAGESOURCE

'N/VVN.,

Cl

L,

Figure 3b: C1 acts as a short to the frequency of interest while isolating the tune voltage from ground. This places the capacitance of VD1 inparallel with C2 and L1. By varying the voltage on VD1, the resonant frequency of the tuned circuit can be changed.

can be tailored to a specific application.Varicap and Selicap are two tradenamesfor the varactor.

Adjusting the tuning voltageThe simplest electronic tuners that are

often found in older TVs and VCRs, usea series of potentiometers (presets) toadjust the "tune voltage". A different po-tentiometer and band selector switch

combination is connected into the circuiteach time a new channel is selected via apushbutton. Some battery operated TVsuse a single potentiometer that is adjust-ed to select a particular channel. This de-sign still uses a band selection switch.Most TVs and VCRs, however, use someform of voltage synthesizer to supply thetune voltage (see Figure 3b).

In newer electronic tuners, one or moreof the components that comprise the volt-

age synthesizer may be contained withinthe tuner housing (the prescaler is oftenpart of the tuner assembly).This can placesome constraints on what the techniciancan do.

This isn't to say that it is impossible totroubleshoot inside of the tuner housing.However, if the electronic tuner itself de-velops a problem it is generally replacedas a unit. The ancillary circuits, however,often can be serviced by the technician.

XTAL FEEDBACK

P LLMICRO

LOAD PULSES

1

CLOSED LOOP

CLOCK

MN1405SHMICRO

LPF

\ /\ /X--11IPI

VOLTAGESUBSTITUTION

POINT

PRESCALER

1/64

TURNER

I 1 I

LA7900

BAND SELECT

UHF VHFRF RF

gip IF OUT

Figure 4: In the Sanyo Model 91 C94N, all components related to voltage synthesis are located outside of the tuner.


TO TUNER

TOMICRO

SWITCHDRIVE

BAND SWITCH

16.5V 17.1V

U -SWITCH

V -SWITCH

Figure 5: The band selector switch activates or deactivates sections of the tuner in response to signals from the control micro.

The voltage synthesizer

I recently repaired the synthesizerboard and varactor tuner in a Sanyo Mod-el 91C94N. In this chassis, all compo-nents related to voltage synthesis are lo-cated outside of the tuner. The mainblocks that will be covered are the pre -scaler, the PLL, the microprocessor, thetuner band selector switch and the low-pass filter (Figure 4).

The band selector switch

In the electronic tuner, some sectionsare common to VL (low band VHF), VH(high band VHF) and UHF while othersections are used exclusively for one ofthese bands. Tuners incorporating a su-perband section follow this rule as well.Tuning of these bands is done separatelybecause the varactor diode has a limitedcapacitance range and therefore cannotcover the entire tuning range of the VHFband (54 to 216MHz which is a 4:1 tun-ing ratio) much less the combined UHFand VHF band.

The purpose of the band selector switchis to enable the appropriate sections of thetuner as needed when a channel is select-ed. In this chassis, the band selectorswitch IC, an LA7900, is controlled bythe microprocessor, an MN1405SH, viatwo lines. The tuner is controlled by the

band selector switch via three lines.When a channel is selected, the micro-

processor, in response to an internal pro-gram, instructs the band selector switch

to open or close one or more of its threeinternal switches. Switching diodes with-in the tuner either pass or block signalsdepending on whether they are forward

TO SWITCHVOLTAGE

Figure 6: Cl acts as a short at the frequency of interest while isolating the switching voltagefrom ground. When Di is forward biased, the lower side of Li is pulled to ground bypassing L2.This lowers the inductance of the tuned circuit raising the resonant frequency.


TO PRESCALER

4

C.)

4

14

2

DIVIDER

)

)

LOADPULSE

GENERATOR

BS gal

4 -BIT WIDEDATA BUS(TO MICRO)

13

LATCH

DIVIDER8

TO MICRO

13 -BIT PROGRAMMABLEDIVIDER

6

111

DIVIDER+3667

IC1103MN60

LATCHB

PHASEDETECTOR

NW TO MICRO

MP TO LPF

Figure 7: One of the more complex blocks in the voltage synthesizer system is the PLL. In this case the internal block diagram of the PLL wasshown on the schematic and proved very helpful in troubleshooting.

or reverse biased by voltages from theband selector switch. The result of thisswitching scheme is that only the sectionsof the tuner that were designed to accom-modate a given band will be activated. Inthis band selector switch, one switchplaces the tuner into the UHF mode, oneplaces it into the VHF mode and the re-maining switch selects between VL andVH when the tuner is in the VHF mode(see Figure 5).

The tuning circuits must make a rela-tively far jump between channel 6 (VL's

highest) and channel 7 (VH's lowest).The center frequency of channel 6 is 85 -MHz and that of channel 7 is 177MHz.The difference is 92MHz. Most channelsdiffer by 6MHz. The reason for this gapis that those frequencies were allotted forother services. For example the FMbroadcast band uses 88 to 108MHz.

The tuned circuits are shifted to a high-er frequency by forward biasing a switch-ing diode which shunts a portion of an in-ductor to ground (see Figure 6). This re-duces the inductance which raises the res-

onant frequency. The reactance of C 1 is

negligible at the frequency of interest soit acts as a short. Its purpose is to isolatethe switching voltage from ground.

Since the UHF band is so far removedfrom the VHF band, it isn't practical totry to tune it on a tuner designed for VHF.As frequencies increase, the problems ofRF design become greater. For this rea-son, most of the UHF stages in the tunerare completely different and separatedfrom the VHF stages. Switching diodesare used to activate or deactivate stages


I

OUTPUT TOSYNTHESIZER 1

UHFOSCILLATOR

INPUT

VHFOSCILLATOR 0-1

INPUT

0 0 0 0 0 0DIVIDER

(DIVIDE BY 64)SP4020

00 0 0 0 0 0

Figure 8: The prescaler circuit divides the frequency of the UHF or VHF oscillator by 64 before application to the PLL. This lower frequency, whilestill related to the original frequency, will simplify the task of the PLL.

as needed. The main stage, which isshared by the UHF and VHF sections, isthe VHF mixer. Once the UHF frequen-cy is converted to the IF it is passedthrough the VHF mixer which in this caseacts as an IF amp.

The tune voltageNow that band selection has been cov-

ered, let's look at individual channel tun-ing. The tune voltage measured at the out-put of the low-pass filter (LPF) rangesfrom a little over 1V to about 24V. Thereis some overlapping of voltages betweenbands. The tune voltage when in the VLband will range from 2V to about 20V. Inthe VH band the range will be from about7V to 20V. In the UHF band it will rangefrom about 2V to 24V. These ranges maybe different for other tuners. Generally,the tune voltage will not exceed 28V.

If the tune voltage line (which will bereferred to as VT in this article) is moni-tored, it can be seen that the voltage willincrease each time a higher channel is se-

lected. Once a higher band is passed into,VT will drop to the floor of that band.Passing into a different band causes dif-ferent tuner sections to be activated so aspecific value of VT won't tune the samefrequency in different bands. If VT ismonitored ahead of the LPF (which in thiscase provides inversion and amplifica-tion) the voltage increments will be small-er while stepping through channels.

The PLI,One of the most important and complex

blocks in the voltage synthesis circuit isthe phase lock loop (PLL). Basic PLL the-ory won't be covered here as it has beenoutlined thoroughly in recent issues ofES&T. The PLL receives instructicnsfrom the microprocessor and feedbackfrom the tuner itself and outputs an errorvoltage which becomes the tune voltage.The PLL IC in this chassis, is an MN6049(see Figure 7). One of the blocks in thisIC is a 13 -bit programmable divider. Thisdivider receives an input signal from the

UHF or VHF LO in the tuner after hav-ing been passed through a prescaler andan on -board divide -by -2 counter.

The prescalerThe prescaler in this chassis is a sepa-

rate shielded module mounted beside thetuner. It consists basically of a 4020CMOS 12 -stage binary counter IC con-figured to divide by 64 (see Figure 8). Itsinput comes from the VHF LO or the UHFLO (depending on which is active).

The LO signal is buffered and ampli-fied by a two -stage amp once inside theprescaler module before application tothe divider. Since the UHFNHF LO fre-quencies are related to the tuned frequen-cy, they can be used as feedback by thePLL to determine to which frequency thetuner is tuned. This feedback signal isessential for proper operation.

Once the feedback signal is divided fur-ther by the divide -by -2 block and the pro-grammable divider, it is compared to astable reference at the phase detector. If


TO TUNER (VT)

FROM PHASEDETECTOR

(PLL IC)

01121

SUPPLYVOLTAGE

Figure 9: The low pass filter amplifies, filters and inverts the tune voltage from the PLL before application to the tuner. The output of the LPF is agood place to open the loop.

the two frequencies don't match, the out-put of the phase detector, which is basi-cally a voltage comparator, will togglehigh or low as needed in an attempt tobring the tuner frequency in line.

Actual locking between the two fre-quencies never takes place. Instead, theoutput of the phase detector responds

quickly each time the tuned frequencyovershoots or undershoots the reference.This holds the tuner frequency within anacceptable tolerance.

The programmable divider

The programmable divider receives aspecific set of data from the micropro-

cessor for each channel. By selecting thecorrect divide modulus or division factor,the divider can convert any incoming di-vided down LO frequency to the refer-ence. This way, no matter what frequen-cy is tuned by the tuner, once the LOfrequency for that channel is divided itwill be suitable for comparison. Since this

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system uses feedback from the tuner tocreate the tune voltage, it must be viewedas a closed loop. As in any loop system,a problem in one section will upset mea-surements in all sections.

This PLL has an on -board oscillatorthat uses an external 3.58 I055MHz crys-tal. This signal is divided by 8 beforebeing passed to the load pulse generator.It is also applied to the microprocessorwhere it is used as a clock signal. Thisway the microprocessor will be locked tothe PLL. Another divider in the PLL di-vides the signal by 3667, giving 976.5625 -Hz before it is applied to the phase detec-tor where it is used as the stable reference.

The load pulse generatorThe input to the load pulse generator,

at pin 5 of the PLL, which is derived fromthe microprocessor, provides timing in-formation for the loading routine. At firstglance with an oscilloscope, the signallooks like a narrow positive -going pulsewith a frequency of about 57Hz. If thetimebase of the scope is adjusted to ex-pand this pulse on the display, it can beseen that the pulse is actually a cluster offour pulses.

Though the PLL uses a 13 -bit divider,there are only four data lines coming fromthe microprocessor to the PLL. The loadpulse generator, which receives a signalfrom the microprocessor as well as a sig-nal from the divide -by -8 divider, work-ing in conjunction with data latch A andfour AND gates, provides a means forsequentially loading latches B through E.If any one of the four data lines is scopedat the same time as the load pulse, it canbe seen that a 4 -bit data burst is presentfor the duration of the load pulse cluster.

The data burst is different on each ofthe four data lines. The data will changeeach time a new channel is selected. Eachlatch will maintain its status after it isloaded thus acting as a data retainer (ormemory). This way the 13 -bit word willbe available at the data input of the dividerduring the interval between load pulses.

The division factorThe following example will show how

the division factor of the programmabledivider is established. The LO frequencyfor channel 4 is 113MHz. Once this isdivided by 64 in the prescaler and 2 in the

PLL's on -board counter, the result will be882,812.5Hz. We know that after divisionin the programmable divider it must equal976.5625Hz to be equal to the reference.We can find the division factor by divid-ing the last number into the first whichgives 904.

Therefore, in order to tune channel 4.the programmable divider must divide by904. The binary equivalent of this num-ber is 1110001000. This number is storedin the microprocessor's built-in memoryat the "channel 4" address. This is only a10 -bit number and could be handled by a10 -bit divider. However, channel 83,which uses an LO of 971MHz, requires adivide modulus of 7768 which translatesto 1111001011000(13 bits).

The phase detectorThe output of the programmable divid-

er, which provides one of the inputs to thephase detector, is available at pin 10. Thedivided -down reference, which is the oth-er input to the phase detector, is availableat pin 9. By scoping these two signals si-multaneously, it can be seen if they sharethe same frequency and phase (which in-cidentally is the job of the phase detec-

be the case when any channel is selected.It makes no difference whether the chan-nel is active or inactive.

The most important parameter of thephase detector output at pin 8 is the aver-age dc value. This value is dependent onwhich channel has been selected. Thisvoltage is applied to the input of a low-pass filter. The low pass filter removesany ac components that were generatedby the phase detector.

The raw tune voltage is taken from a28V Zener diode D1121. This voltage isapplied to a voltage divider consisting ofR1122, R1123, and Q1123 (see Figure 9).The voltage that is routed to the tuner con-trol input is tapped from this divider byR 1 1 2 1 . Transistor Q1123 serves as a vari-able resistance. It is also an inverter.

When it is turned fully on, VT will beat its lowest point. When it is fully off,VT will be at its maximum. Normally, itwill be partially on, holding VT some-jwhere in between. Notice that the LPF isactive and uses a Darlington configura-tion hence it has a high gain. A change ofonly a fraction of a volt at the input resultsin a change of several volts at its output.

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Troubleshooting secondaryvoltage circuitsBy Homer L. Davidson

Determining the cause of chassis shut-down, or overloaded power supply cir-cuits, or isolating defective componentsin the secondary circuits of the horizon-tal output transformer can consume agreat deal of a technician's valuable ser-vicing time. Overloaded circuits in any ofthe scan -derived voltage sources cancause chassis shut -down, which frequent-ly makes the job of diagnosing a problemmore difficult.

A shorted or leaky component in anyof the circuits in a TV set can result infailure of another circuit. A defective sil-icon diode rectifier or electrolytic capac-itor in any of the voltage sources suppliedfrom a secondary winding of the hori-zontal output transformer can cause shut-down or improper circuit operation.

The secondary winding of the horizon-tal output transformer provides power tothe horizontal output and driver circuits.In many sets, the low voltage power sup -

Davidson is a TV servicing consultant for ES&T.

Figure 1. The secondary voltage sources areflyback.

ply circuits may operate off of a secondarywinding of the flyback as well (Figure 1).

These various supply voltage circuitsmay be derived from separate transformerwindings, and may be regulated and fil-

derived from several windings upon the IHVT

tered by silicon diodes and electrolytic fil-ter capacitors. Transistor or zener diodevoltage regulation, or a combination oftransistor and zener diode regulation, canbe used in the critical voltage circuits. In

BRIDGERECTIFIER

PART OFT402

FLYBACK

800p.F

D101 C1011000µF

B+ 112VHORIZONTAL OUTPUT

ANDDRIVER TRANSISTORS

+220VIIMP. BOOST VOLTAGE FOR CRT

COLOR OUTPUT TRANSISTORS

Figure 2. The boost voltage (+220V) in this circuit was taken from a secondary winding of the norizontal output transformer T402.


.111111. 2 HORIZ +12.6V CHROMA IC+112VA DRIVER 62 +112VB HORIZ OUTPUT +11.9V CHROMA CIRCUITS

+220V BOOST V. CRT7

3 +12.5V IF PROCESSOR8COLOR OUTPUTS 9 +12.1V IF-AGC

+25V VERTICAL OUTPUT4 +9.5V VERTICAL PREAMP-VERT INVERTERIC+23.8V VIDEO IC AMP

105 +20.4V SOUND IC-VIDEO - 11

SYNC SEP-TUNER- 12 +7.1V IF PROCESSOR -IF PREAMPSOUND OUTPUT

Figure 3. The voltage sources shown here numbered, are powered by the flyback secondary. These sources provide power to most of the circults in this set.

Figure 4. Older flybacks provided high voltage, screen and focus voltages from their secondarywindings.

some cases regulation of voltage sourcesis achieved using only zener diodes.

The various voltage sourcesIn many sets the low -voltage power

supply circuit consists of a bridge rectifi-er network, a high voltage filter capaci-tor. and dc voltage fed to the horizontaloutput transistor and driver circuits. Thevoltage source feeding these two circuitsmay be raw dc taken directly from the dcpower supply, or it may be regulated byan IC voltage regulator. Usually the volt-age supplied to the horizontal output tran-sistor circuits is the highest dc voltagefound in the set, except for boost voltage.

A typical flyback transformer secon-dary circuit supplies many different volt-age sources. In the circuit shown in Figure2, a 220V boost voltage feeds the CRT,color outputs and HV shutdown returncircuits. A separate secondary winding

supplies ac voltage to a silicon diode anda 47g, 180V electrolytic capacitor. Notethat the working voltage of the filter ca-pacitor is far higher than those found inthe rest of the dc sources.

Another secondary winding suppliesflyback voltage to a silicon rectifier. Theoutput of this source is used to provideseveral different voltages via regulationemploying transistors and zener diodes.and filtered using electrolytic capacitors.Most secondary circuits employ silicondiodes for half -wave rectification. InSams Photofacts, the various voltagesources are identified by number and caneasily be located on the main schematicby the number (Figure 3).

lf, for example, you are servicing a TVset with a good picture but no sound, youwould check the secondary power supplylist and see what number circuit suppliesvoltage to the audio output circuits. You

would then locate that number on theschematic to locate the point where theoutput of the supply appears.

The next step would be to check thevoltage at that point. If the voltage is in-correct, the problem might be a defect inthe supply, or a defect in the circuit thatis supplied by that voltage that is causingan overload.

If the voltage is correct, the cause of theproblem is not the supply. Keep in mindthat when one voltage source is missingseveral different stages or circuits may beinoperative.

Older flyback circuitsIn older horizontal output transformer

circuits, very high HV, focus, screen andboost voltages were found in the secon-dary circuits. In some TV chassis, highvoltage was developed from the large fly-back winding with a tripler unit supply-ing HV to the CRT.

The focus and screen voltages are de-veloped from a high resistance networksupplied by the high voltage source. An-other secondary winding, or a tap off ofthe bottom leg of the horizontal outputtransformer, supplied boost voltage to thepicture tube circuits (Figure 4).

In later model TV sets, the integratedhigh voltage transformer (IHVT) was in-troduced. This unit comes with HV di-odes and capacitors mounted inside theflyback to develop high voltage for thepicture tube. The high voltage resistornetwork from the HV output suppliesboth focus and screen voltages for theCRT. Still later, several different sec-ondary windings were added to the hori-zontal output transformer to supply volt-ages to other circuits in the TV chassis.

Overloaded circuitsToday, the IHVT transformer provides

many different voltage sources derived


from the secondary winding. These coilsare wound on the same transformer coreas the high voltage winding. If a chassisstarts up and then shuts down, a likelycause is a leaky silicon diode in the sec-ondary circuits.

Sometimes by carefully observing thescreen as you turn the set on you can deter-mine what circuit the trouble exists in. Anoverload in the secondary voltage circuitsor in a circuit that is supplied by the sec-ondary can cause the chassis to shut downat once.

For example, if a 25V source feeds thevertical output IC, a leaky output transis-tor or IC can cause an overload on that25V source. A direct short or low resis-tance may damage the connecting silicondiode and isolation resistor before chas-sis shut -down occurs. Often, the chassiswill shut down if a component in the ver-tical circuit is causing an overload.

In the circuit shown in Figure 5, if ca-pacitor C322 (1000µF) had a direct short,D522 might become damaged, or thechassis might shut down before D522 in-curs any damage. A leaky C335 (1000µf)electrolytic capacitor in the output yokereturn circuit may delay the shut down ofthe chassis and cause a horizontal whiteline on the raster.

The sound was weak and distorted in aPanasonic AGP159 chassis. The picturewas normal. The voltage at pin 9 (Vcc) ofthe sound output IC, IC201 was only5.4V. The voltages on both sides of R2 I0were low. I traced the low voltage sourceback to the flyback secondary 15Vsource. Diode D507 and capacitor C516checked out normal. I concluded thatIC201 was leaky. All of these tests weremade by monitoring voltages during turn -on and shut -down operations.

I unsoldered one end of R210 to isolatethis supply from the circuit it supplies, tosee if the voltage source was the problemor if the IC was defective. When I againapplied power to the set, the secondary15V voltage source measured 15V (Fig-ure 6). A resistance measurement frompin 9 to ground verified that IC201 wasleaky. IC201 was replaced with an ECG -1789 universal IC replacement.

Chassis shut -downA low resistance leakage loading down

one of the voltage sources powered by theflyback secondary may cause chassisshut -down in sets that have the latest

00>-

0

`Cg

N

VVV\t

Na

U.NCr)V) 00U0

.)L,uLlifoL)

Figure 5. A leaky vertical output IC. IC301, may load down the 25V secondary source. causingshut -down.

IHVT flybacks (Figure 7). The chassiswill shut down if a horizontal deflectionIC that derives its power from the flybacksecondary becomes faulty.

The same type of horizontal deflection

IC fault might not cause shut -down if itssupply voltage comes directly from theac -line -powered low voltage power sup-ply. When faced with a set that is inoper-ative because of shut -down, try to deter -


CC

NC

wC/)

rY-YYLH ,

3z

mine what circuit might cause chassisshut -down if it becomes overloaded.Check to see what type of voltage sourceis feeding the horizontal deflection IC.

For instance, if you see a horizontal

white line on the screen before chassisshut -down, it's a good bet that a mal-function in the vertical circuits caused theshut -down. In such a case, go directly tothe vertical circuits and isolate the volt -

Figure 6. When one end of R210 was discon-nected from the circuit in this set, the secondaryvoltage source returned to normal. The prob-lem was found to be a leaky sound output IC,IC201.

age source feeding the vertical outputtransistors or IC. Desolder the vertical ICvoltage supply pin to isolate the supplyfrom the IC. Likewise disconnect the iso-lation resistor between output transistorsand the voltage source.

If the chassis starts -up and remains op-erating (or it may shut down after a fewminutes) check for a leaky diode in thesecondary voltage source. Refer to theschematic to locate the isolation resistorand filter capacitor. The resistor mayshow signs of overheating and burnedmarks. An open electrolytic filter capac-itor will have very low voltage at the volt-age source.

The causes of shut -down are difficultto locate if the horizontal deflection ICcircuits are fed from the secondary volt-age source. The horizontal circuits mustoperate in order to generate the secondaryflyback voltage sources. When the setgoes into shut -down, you must determineif the secondary voltage sources are caus-ing the shut -down or if the problem iscaused by defective horizontal circuits.

The horizontal oscillator, count -downcircuits and horizontal deflection IC canbe checked by supplying a voltage froman external power supply or batteries tothe horizontal circuits. With the externalpower source connected, use the oscillo-scope to see if there is a horizontal outputwaveform at the deflection IC. Proceed tothe rest of the horizontal circuits to deter-mine if they are working.

Secondary current testsIf the set has shut -down and you don't

know if the problem is a faulty voltagesource that derives its power from the fly-back secondary or a faulty circuit that'sloading down the supply, disconnect oneend of the silicon diode that provides volt-age to the secondary voltage source. Dis-connect only one end of the diode andcheck to see if the set will stay on.

All secondary voltage sources can beisolated using this method. Of course, ifyou disconnect the voltage source thatfeeds the horizontal deflection circuits,the chassis will remain in shut -down. Re-member this same voltage source may


Figure 7. Chassis shut -down may occur when one of the circuits supplied by the secondary ofthe flyback transformer becomes leaky and loads down the supply.

supply voltage to several different cir-cuits. By removing one end of each sili-con diode in turn, you may be able to iden-tify the overloaded circuit. Determinewhich components are causing the defec-

tive circuit using resistance and transis-tor -diode tests.

Another method of determining if thereis an overload is to insert a current meterin series with the voltage source or sili-

con diode. Disconnect the positive end ofthe diode rectifier and insert the milliam-meter. Some schematics have the totalcurrent draw marked on the various volt-age sources. If the current is high on anygiven circuit, check to see if a faulty com-ponent is causing an overload (Figure 8).If the total current was specified to be20mA and you measured 30mA or more,suspect a leaky component in the circuitsupplied by that voltage source.

Voltage and resistance testsVoltage measurements in the secon-

dary circuits can determine if a compo-nent in the voltage source is faulty, or ifcircuits external to the power supply areleaky or shorted. Extremely low voltagesmay indicate an overloaded circuit or anopen filter capacitor. A leaky filter capac-itor in the voltage source can shut thechassis down. Leaky transistors or zenerdiode regulators can cause chassis shut-down as well.

Resistance measurements across thelow -voltage sources may turn up a leakycomponent or voltage source. If voltageand resistance measurements at the ter-minals of a voltage source reveal low volt -

PART OF T402FLYBACK

D101

20mA

810mA

T100µF

D102

20V

ZD101

30(2

+.1

SW +220V BOOSTCOLOR OUTPUTS

CRT CIRCUITS

11111.. +25V VERT OUTPUTHORIZ AND VERTCOUNTDOWN IC

illob +20V VERTICAL -

220µFSOUND -VIDEO -TUNER

Figure 8. You can check to see if a circuit is causing an overload by disconnecting the positive terminal of the silicon diode that's used as a rec-tifier for that source and inserting a current meter in series with the output voltage source.


0 >z >

0

co

w

')>0

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C

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C

1.

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7,cr

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c.) Z ci z4 cc o z 8ow ~oz1-3 (..) §

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o. cn

O

crC.)

14 -III

Figure 9. Shorted CR3104 and leaky CR3105 caused the RCA CTC146 chassis to shut -downat once.

age and resistance to common ground, dis-connect one end of the diode to determineif the voltage source is defective or if theconnected circuits are defective. Monitorthe suspected voltage source when theproblem is chassis shut -down. Note if thecorrect voltage is there before shut -down.Most likely the voltage source is normalif correct voltage is found before shut-down. Suspect leaky components in thevoltage source circuits when the voltageat the source terminals remains at OV.

A diode test of silicon diodes, regula-tor transistors and zener diodes may turnup the defective component. Measure theresistance across the secondary electro-lytic capacitor to see if there is leakage orlow resistance. When low resistance isfound across the secondary voltage source,disconnect the external circuit or check itfor leaky or shorted components.

In an RCA CTC146 chassis, the TV setwould come up and immediately shut-down. The 140V, 160V, and 185V sourceswere fairly normal. The standby voltagewas very low. It should be around 12V.According to the schematic, the standbyregulator (Q3107) had sufficient inputvoltage to the collector terminal. At firstI suspected that the regulator transistorwas open, but it tested normal in and outof the circuit.

Resistance across CR3105 and CR-3104 in the base circuit of the 12V regula-tor measured below 2712. Further check-ing of these components out of circuitrevealed that CR3104 had a direct shortacross its terminals and CR3105 wasleaky (Figure 9). Replacing both the 6.8Vand 5.6V zener diode regulators solvedthe chassis shut -down symptom.

Secondary open filter capacitorsVery low secondary voltage sources

can be caused by a leaky silicon diode,burned isolation resistor, or open filtercapacitor. Check the suspected diode andresistor with a resistance test. The dried-up or open filter capacitor in the secon-dary circuits may be a little more difficultto locate. You could try an in -circuit ca-pacitor test, but this measurement is fruit-less, since the surrounding resistances inthe output voltage source are low.

When the voltage of a source is low,and the chassis is not in shut -down, turnoff the set, disconnect the line cord andshunt a known good electrolytic capaci-tor with correct working voltage across


10.0 +23V

PART OFT402

1000µF T 4.70

101(0

1200

47µF

ZD1

200

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1110. +20V

2700

0601VOLT REG

ZD212VREG

Ob. 12.5V

101, +11.9V

0.1µF

aliblo 12V

Figure 10. Check for leaky or open voltage regulator transistors and zener diodes in the defective scan -derived voltage sources.

the suspected one. Apply power to the setand check to see if the voltage returns tonormal. If so, remove the open capacitorand test it out of the circuit. If this testconfirms that it's bad, replace it.

Although you can remove the suspect-ed capacitor and test it out of the circuit,this test may indicate that the capacitor isnormal, even if there's a broken internalconnection. The broken connection maybe temporarily restored by the jostling ex-perienced by the capacitor as it's beingremoved from the board. Shunting thecapacitor in the circuit is much quickerand accurate, because it doesn't disturbthe condition of the electrolytic capacitor.

Identifying secondary voltage sourcesIt can be very difficult to service secon-

dary voltage sources without a schemat-ic. In some sets, the voltages of the sourcesare stamped on the printed circuit board,making things a little easier. Sams Photo -facts list the various voltage sources bynumber. By locating the correct silicon

diode in the secondary voltage sources,you can locate the diode on a chassis lay-out chart.

Critical voltage sources can be mea-sured or monitored from the positive ter-minal of the silicon diode. Look for thesesecondary components on the printed cir-cuit board near the flyback transformer.If the schematic is not available, it maybe possible to trace out the various sec-ondary windings from the transformer tothe corresponding silicon rectifier, andcreate a rough schematic of your own.

Secondary voltage regulatorsYou may find several transistors and

zener diode regulators in the various sec-ondary low voltage circuits. In the 20Vsource of the circuit of Figure 10, a 19Vzener diode regulates the 20V source.This voltage source is fed to the first andsecond video amp, sync, tuner, and soundoutput circuits. The 11.9V source has atransistor as voltage regulator (Q601).The 11.9V source feeds the chroma IC cir-

cuits. The 12V source is regulated with a12V zener diode. Do not overlook thepossibility that the problem is an open orleaky transistor or zener diode regulatorif the voltage from a particular secondaryvoltage source is low.

ConclusionWhen servicing voltage supply circuits

that derive their power from a horizontaloutput transformer, determine if the hor-izontal oscillator or deflection IC is pow-ered directly from the low voltage powersupply or if they're powered by the secon-dary voltage source. Chassis shut -downproblems are easier to service if the sup-ply voltage for the deflection IC comesfrom the low -voltage power supply.

The horizontal circuits must be fullyoperational if the supply voltage of de-flection IC is taken from the secondaryvoltage sources. Check for leaky compo-nents in the secondary voltage sourcesand overloaded components in the con-necting TV circuits. IN


PhotofactsThese Photofact folders have beenreleased by Howard W. Sams & Co. forFebruary 1995.

FEBRUARY

CROSLEYCT1320W401 3437

CT1320W404 3437

13Y401-00AA 3437

GECTC-136AC 3436

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VG7720 VCR -260

8-1932A01 3436

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19GX310N01 3436

MAGNAVOXPR1910C123 3426

TP2590B101 3429

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19G601-00AA 3426

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PANASONICADP237 3427

ALEDP238 3430

A LEDP240 3430

CT-F33L6LS 3430

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CT-19R11S 3427

CT-27SF31S 3430

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CT-31 SF3 I S 3430

CT-31XF31CS 3430

PV -4800 (sim to) VCR -260PV -4800-K (sim to) VCR -260

QUASARADC233 3428

ALEDC233 3438

ASEDC233 3438

SP2000K 3438

SP2026K 3438

TP2006CK 3428

TP2006K 3428

VH5480 (sim to) VCR -260VH5480-K (sim to) VCR -260

SHARP19F-M1OOM 3435

1 9F -M120 3435

19F -M150 3435

27F -S40 3432

27F -S50 3432

27F -S100 3432

27F -S120 3432

SONYKV-MT2000 3434

KV-20M10 3434

KV-21R10 3434

KV-2180R 3434

SCC-G92B-A 3434

SCC-G93B-A 3434

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Computer Corner

Networking basicsBy David F. Norman

Even experienced personal computerusers often feel that computer network-ing is a real mystery. Networks can be in-credibly complex, but the basic conceptis simple. Let's take a look at what net-works are and what they can do for youand your customers.

For the small electronics service cen-ter, selling, installing and servicing localarea networks (LANs) can add some tothe bottom line, even if you service asmall market area. Frequently, computerexpertise, defined as staying one pageahead of the client, is hard to come by insmall towns and rural areas. The dealerwho is already selling or planning to han-dle a few computer accessories will findthat networks are one area where mailorder is weak. If you are already compe-tent at setting up computers for new users,networks will be a natural for you.

However, before you start selling them,you need to set up your own LAN. If youcurrently use more than one computer inyour business, you already have most ofwhat you need.

Actually, you may be already doingsome simple networking and not evenrealize it. Networking is connecting com-puters together in order to share files andresources. If you use a modem to accessa bulletin board or an on-line service suchas Compuserve or Prodigy, you are en-gaging in a type of limited networking.When you take a file from home to theoffice or take a disk to another desk justto use the laser printer, you are using atype of network often called "Sneaker -net." As long as this doesn't become ahassle, this may be all the networking youever do or ever need. However, there aremany circumstances that require more ef-ficient connections between computers.

A small network systemLet's consider the owner of a small

business with three computers in his of-fice. He uses a computer to track his cli-

Norman is an independent servicing technician and a com-puter and security consultant.

MODEM

BOSS'PC

WORKSTATION

DOT MATRIX

(OPTIONAL)

DEDICATEDSERVER

LASER PRINTERPRINTER

(SHARED)

DOT MATRIX

(OPTIONAL)

OFFICE MANAGERPC

WORKSTATION

DOT MATRIX

WAREHOUSEPC

WORKSTATION

DOT MATRIX

(OPTIONAL)

Figure 1. A simple network such as this one can help a business keep computer informationflowing smoothly.

ents, run spreadsheets for projections, andwrites business correspondence. The of-fice manager keeps the books, does in-voicing, figures the payroll, and polishesthe letters written by the boss. The ware-houseman uses a computer for inventorycontrol and to transmit orders to vendors.

Obviously, the boss needs to knowwhat is going on with the inventory, bill-ing and payroll. The office manager needsup to date information on what has beenordered and sold, and also needs easy ac-cess to the correspondence requiring edit-ing. The warehouseman must be able toaccess customer account status or the of-fice manager has even more work to dodeciding whether to ship to a question-able account.

Each of the departments needs infor-mation from the others or efficiency suf-fers and so does profitability. Believe itor not, there are businesses being operat-ed in just this manner. If not for sneaker -netting, the computers would almost be

more trouble than they are worth. Thereis a simple solution.

Networking the computersThe owner looks around and decides to

add one more computer. This computersits in a corner and does nothing exceptact as an administrator of the other com-puter resources. Wasteful, you say? Notat all. While it is possible for a server tobe non -dedicated, meaning it can be usedfor computing as well as managing net-work resources, a dedicated configura-tion is more efficient (see Figure 1).

While there are many different networktopologies, or ways of connecting thehardware, Figure 1 uses the bus topologyfor simplicity.

At one end of the bus, sits the comput-er in the owner's office. Next down theline is the server. Then comes the officemanager's computer and at the end of theline is the warehouse.


In the simplest of all configurations,which many experts believe is the bestway to run a network,each workstationhas its own hard drive. Program files (thefiles necessary to run an application) areinstalled on each workstation and onlydata files (those that contain informationadded by operators) are stored on the serv-er. Generally speaking, this configurationlessens network traffic and speeds oper-ation. In a small office, there might be lit-tle advantage to keeping program files offthe network, but having more than one setof program files can keep things going incase of a breakdown of the server. Thisassumes that proper backups of data filesare made frequently.

Okay, how does all this tie together?

Network hardware and softwareA network consists of two parts: hard-

ware and software. The hardware consistsof the computers, printers, network adap-ters, and cable which tie it all together.The software is what makes it all work.

After the adapters are all tied togetherwith cabling, the network software mightbe considered the language and the rulesthe computers use to get things done.

If two workstations try to do the samething at the same time, the network soft-ware must resolve the conflict without"locking up." If a file is already in use andanother computer tries to access it, theremust be something to lock a file so thatthe information added doesn't conflictwith simultaneous entries. When a print-er is shared by several computers, a printqueue must be formed to keep each com-puter free to do other work while printingis in progress.

Network software also makes provi-sions for security. If the boss has files hewants to keep secret, the network limitsaccess. Employee records are often con-fidential; casual access could cause allsorts of problems. Most networks allowtracking of users by file and time. Thus,who does what is a matter of record. Wiseemployers seldom use all of the informa-tion that can be gleaned from networkrecords, but the controls allow abuses tobe documented and controlled.

Additional network featuresDepending on the network, there are

many other bells and whistles which canbe used as necessary. Most networks al-low sending "live" messages, electronicmail or both. It is a relatively simple mat-ter to set up a network for remote access.

A salesman on the road can access thesystem via telephone modem to place or-ders, check availability or status of an ac-count, leave a message for later retrieval,or check his own mail. The possibilitiesare almost unlimited-even with an inex-pensive network.

Tying it all togetherHere's a description of a business pro-

cess that can be handled easily using thenetworked computers. The owner wantsto send a letter offering a new service toall accounts which are over a certain levelof purchases with good credit records.

He composes a letter and saves it in adirectory for later editing and leaves amessage to the office manager requestingthat the letter be merged with the appro-priate customer data base.

When time permits, the office manag-er executes the request and sends a mes-sage to the warehouse advising of thisnew service being offered.

At the same time, an order is receivedby telephone and routed to the warehouse.The warehouseman checks to see that theaccount meets automatic shipping guide-lines and checks for any special shippingrequirements noted on the account's in-formation sheet. Finally, he makes an or-der entry, which removes the items soldfrom the perpetual inventory, and gener-ates a shipping invoice on the printer.

Since this business is tightly run andbilling is done daily offering discounts forearly payment, the office manager usesthe information from the order to send astatement to the customer.

At the end of the day, the office man-ager develops a sales and inventory reportand prints it on the office laser printerwhich can be shared by any station that ison the network.

That's how it works. There is no lostmotion in this system. The flow of infor-mation goes smoothly and is instantlyavailable to all who need it.

A networkSo what does all this efficiency cost?

Less than you would think.

A network consisting of a server andthree workstations could cost as little as$1000 or thereabouts for the networkcards, cabling, and software. This, ofcourse, doesn't count the costs of thecomputers, monitors, and printers. Itcould also cost a lot more. There are evensome "poor boy" networks which use ser-ial or parallel ports and are quite inex-pensive. Unfortunately, there are usuallydeadly limits and drawbacks to such sys-tems. The last thing you need when youare in search of efficiency is a balky,crash -prone, slow, and limited -functionnetwork. The real thing is always better.

The businessman using several com-puters for simple processes such as wordprocessing, accounting, and inventorytracking, may find that networking canactually save money by using slower, andcheaper, computers for these mundanechores and put his money into the sharedperipherals such as laser printers andhigh-speed modems. Not everyone needsa 386 or higher machine.

In a future article we will get into thenuts and bolts of setting up an actual sys-tem, using typical software and hardware.

Test YourElectronicsKnowledgeAnswers to the quiz(from page 19)

1. Write (What)

2. Difference of potential (Do)

3. Yoke (You)

4. Kelvin (Know?)

5. Antenna (And)

6. Transfer Function (Test)

7. Y Signal (Your)

8. Electrolyte (Electronics)

9. Kilowatt Hour (Knowledge)

10. Y Connection (Yes!)


What Do You Know About Electronics?

Working with fractionsBy Sam Wilson

The word "cancel," as used in this arti-cle, means division of one quantity byanother. When I was in school one of myteachers would get very upset at the men-tion of the word in relation to fractions. Ihave forgotten why it is supposed to beso bad, but, I remember the message.

I guess I can get away with it here bydefining "cancel" as a form of division inworking with fractions.

As shown in Figure 1, fractions can berepresented two different ways: shillingand case.

When you do work for a book publish-er you are usually constrained to use shill-ing fractions. That makes it difficult toshow unit conversions. It also makes itdifficult to rationize units in equations.

For a very simple example consider thecalculation of earnings for a worker whois paid by the hour.

Example:A worker earns $8.36 an hour. If he

works 27.5 hours in one week, how muchdoes he earn?

Solution:Earnings = hourly wage x number of

hours worked.I have shown the solution two ways in

Figure 2.

There is a certain amount of opinion inwhat I say here. I believe the solution witha case fraction to be the better way ofshowing the calculation. It is a better wayof showing how the units can be cancelledcompared to the method that uses theshilling fractions.

That is especially true with more com-plicated calculations.

There are good reasons for using shill-ing fractions in books: they are easier totypeset and they do not goof up the linespacing. In most cases that is acceptable,but, they do not do the job when you wantto show certain math solutions. (If youhave an opinion about this be sure to writeand cast your vote.)

Note how the units (hours) are can-celled in both solutions.

Wilson is the electronics theory consultant for FS&T

SHILLING FRACTION: 3/4

CASE FRACTION: 34

Figure 1

Figure 2

WITH SHILLING FRACTION:

EARNINGS = 8.36 DOLLARS/W-1:4X 29.5 H S = 246.62 DOLLARS

WITH CASE FRACTION:

EARNINGS = 8.36 DOLL S X 29.5 HO ?S = 246.62 DOLLARS

70 11/J X 1 H R X 1 1./ X 5280 FEET- 102.67 FEETH R 60 M/ 60 SEC SEC

Figure 3

X MILE'S x HdUR Mite 5280 ftSPEED - HOUR 60 MIS x60 SEC X MILfiv

SO: MILES FEET' HOUR X 1.467 =SECOND

TO CHECK THIS EQUATION -30 MPH X 1.467 = 44 fps

Figure 4

After cancelling the hours the only unitleft is the dollars and that is what you arelooking for in the solution.

In some books-and in this article-that is called "rationalizing units."

Of course, with the sample problem thesolution is very easy. Let's look at a morecomplicated example.

Example:How many feet per second does a car

go when it is moving at a speed of sev-enty miles per hour?

Solution:From this point on I will abandon solu-

tions with shilling fractions. To solve thisproblem you need to remember that thereare 5280 feet in one mile. Also, you needto remember that there are 60 minutes inan hour and 60 seconds in a minute.

I have shown the solution in Figure 3.Again, take note of the method used tocancel units.

The word "per" means to divide. It isimportant to observe that the speed is not


A _ CB D

-4- Figure 5Figure 6

30 MPH = 70 MPH44 fps X

30 (MPH) TIMES X = 70 (MPH) TIMES 44 (fps)

X = 70 MPH x 44 fps30 MPH

X = 102.67 fps

written as 70 miles/hour. In the solutionit is written as 70 miles divided by hours.It makes the cancellation of equal unitseasier to locate in the equation.

You don't have to remember whetheryou need to multiply or divide with thismethod. If you perform the calculationwrong you won't come out with the cor-rect units in the solution.

There are other applications where casefractions do a better job. When you derivean equation it is a quick method of check-ing to see if you got it right. I can showthat with the same type of problem thatwas just worked.

Example:Derive a general equation showing how

speed in miles per hour can be convertedto feet per second.

Solution:Refer to Figure 4. In the equation, MPH

is miles per hour and fps is feet per sec-ond. The resulting equation is correctbecause it gives the answer in feet per sec-ond. The solution gives a general -caseequation that can be used with any speedin MPH.

Having reviewed the method of ratio-nalizing units I will use the technique forworking problems in electronics. Thatwill have to wait for a near -future article.

Working with ratios and proportionsThis is another example of an applica-

tion where case fractions do a better job.A number divided by another number

is a ratio. A proportion looks like this withshilling fractions: A/B = C/D. It is some-times shown as A:B = C:D where A andD are called the "extremes," and, B andC are called the "means."

Figure 5 shows the same proportionwith case fractions. Read the equation this

way: "A is to B as C is to D."It will not work unless there is a direct

connection between the quantities that arerepresented by the letters. For example,you can't say that pigs are to chickens aspossums are to Broadway plays.

People who write entrance tests for col-lege feel that there is something deep andspecial in a proportional kind of relation-ship. The theory is that highly -intelligentpeople can quickly discern relationshipsbetter than those less gifted. For some rea-son-never fully explained to me-thereare people who do not do well on any kindof test who are often able to commandvery high salaries.

Here is an example of the type of ques-tion used on those tests:

Pen is to ink as pencil is to:A. BauxiteB. Graphite*C. WaterD. WineE. lead(The answer is not lead.)In science and related subjects-like

electronics-the use of proportionsserves a practical purpose. You can solvemany problems with it.

In the last problem it was necessary tofind a relationship between miles per hourand feet per second. To solve the problemyou need to know that there is some directrelationship between the two. One of thefirst relationships I was required to learnin school was: "30 miles per hour equals44 feet per second."

Armed with that you can work the prob-lem as shown in Figure 6 by setting up theproportion: 30MPH is to 44 fps as 70MPH is to x fps. The product of the meansis set equal to the product of the extremesand the equation is solved for x.

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BooksSurface Mount Technology, By

Rudolf Strauss, Butterworth Heine-mann, 364 pages, $69.95 hardcover.

Surface Mount Technology has had aprofound influence on the electronicsindustry. Change has involved the use ofnew materials, techniques and manufac-turing processes, and has resulted in a sig-nificantly new approach to electronicsassembly. This is a wide-ranging guide tothe subject by one of the founders of thetechnology and covers SMDs, soldering(including reflow- and wave -soldering),component placement, cleaning and qual-ity control.

The author, Rudolf Strauss, wasresponsible during a lifetime at Fry Groupof Companies for a number of the keyinnovations that contributed to surfacemount technology, including the wave -soldering principle, the first wavesolder-ing machine, and a number of solderingfluxes and preparations.

Strauss' book aims to explain the prin-ciples of surface mount technology forpractical application, rather than dwellingon theory, and so should find use in anyfacility employing SMT as well as thoseconsidering switching to it.

Book topics include: Why SMDs?, TheSMD Family, Soldering, Wavesoldering,Reflow soldering, The Circuit Board,Component Placement, Cleaning QualityControl and Inspection, and Rework.

Butterworth Heinemann, Newton, MA 02158-1626

The Technical Career Navigator, ByRay Weiss, Prentice Hall PTR, 270pages, $19.95 paperback.

Ray Weiss helps technical profession-als find a job, keep a job and advance theircareers in his new book, The TechnicalCareer Navigator.

The Technical Career Navigator showstechnical professionals how to take con-trol of their careers. Using an easy -to -read, informal and entertaining style,Weiss offers vital information that men-tors used to give. Weiss, a technical pro-fessional himself, addresses anxietiesfound in today's technical industries. TheTechnical Career Navigator features 138keys to success-straightforward advice,insights, unwritten rules, conceptualviews. Some of the topics covered

include: Be Noticed-do your work andmake sure you're noticed; Burnout-Don't burn out, grow; Creativity Is NotEnough-ideas need to be implemented;Pat yourself on the Back-know yourworth; Your Worst Enemy-Know yourweaknesses and bypass them.

Ray Weiss is a former computer andlogic designer, a former programmer andproject manager. He spent the last 10years in the electronics trade press as atechnical editor. Weiss has a BSEE fromthe University of Southern California. Hehas also worked as a technical headhunterlearning the ins and outs of technicalemployment.

Prentice Hall, Simon & Schuster Education Group,

Englewood, NJ 07632

The Internet Book, By Douglas E.Comer, Prentice Hall PTR, 336 pages,$24.95 paperback.

Prentice Hall announces the publica-tion of The Internet Book: EverythingYou Need to Know About ComputerNetworking and How the Internet Worksby Donald E. Comer.

The Internet Book puts the whole net-working story together. Comer, anInternet expert and educator, examinescomputer networking and the Internetfrom a nontechnical perspective and putsit in terms that anyone can understand.Comer focuses on fundamentals of net-working. The book explains how com-puters communicate, what the Internet is,how the Internet works, and what theInternet can do for you. By the time youfinish reading, you will know what theInternet is, how it can be used and whypeople find it so exciting. You will alsounderstand the origins of the Internet andwhy it continues to grow so rapidly. Mostimportant, you will understand the poten-tial ways in which the Internet can changeyour life.

The Internet Book answers the question"What is the Internet?" in the broadestsense. The book examines the origins ofcomputer networking and its applicationto everyday problems. It focuses on theservices that the Internet provides andhelps you understand their importance.The book doesn't overwhelm you withdetails. Using easy -to -understand analo-

gies, examples and nontechnical lan-guage, Corner builds a foundation forunderstanding computer networking interms of your everyday experiences.

The Internet Book is organized into foursections. The first section introducescommunication system concepts and ter-minology such as digital and analog com-munication, universal service, and bina-ry data encoding. The second sectionreviews the history of the Internet and itsincredible growth. The third sectiondescribes basic Internet technology andcapabilities. It examines how Internethardware is organized and how softwareprovides communication. The final sec-tion describes services currently avail-able on the Internet. For each service thebook explains how the services work andhow each service can be used.

Douglas E. Corner is a professor atPurdue University, where he teaches pop-ular courses on computer networking.

Prentice Hall, Simon & Schuster Education Group,

Englewood Cliffs, NJ 07632

Practice Tests for CommunicationsLicensing and Certification Examina-tions: The Complete TAB Reference, BySam Wilson and Joseph A. Risse,TAB/McGraw Hill Inc., 400 pages,$24.95 paperback.

The new TAB/McGraw-Hill release,Practice Tests for CommunicationsLicensing and Certification Examina-tions: The Complete TAB Reference, is astudy guide to passing all of the impor-tant licensing and certifications tests inthe field of communications.

Authors Sam Wilson and Joseph A.Risse include full-length practice exams,along with answers and mathematicalsolutions, for: General Radio OperatorLicense; Amateur Radio Technical ClassLicense; Marine Radio Operator Permit;ISCET Associate -Level Certification;ISCET and ETA Journeyman Comm-unications certifications; GMDSS; RadioTelegraph Certification; Radar Endorse-ment; ETA Associate -Level Certifi-cation; SBE and NICET Certifications.

Both authors of actual CET exam ques-tions, Sam Wilson and Joseph A. Rissehave collaborated on a companion vol-ume, the February 1995 TAB/McGraw-


Hill release, Communications Licensingand Certification Examininations: TheComplete TAB Reference. Wilson, a resi-dent of Melbourne, Florida, is a formerCET Test Consultant for ISCET. Risse, aresident of Dunsmore, Pennsylvania, isan electrical engineer.

TAB/McGraw-Hill, Inc.. Blue Ridge Summit. PA

17294-0850

Communications Licensing andCertification Examinations: The Com-plete TAB Reference, By Sam Wilsonand Joseph A. Risse, TAB/McGraw,Inc., 480 pages, $44.50 paperback.

Communications Licensing andCertification Examinations: The Com-plete TAB Reference provides electronicstechnicians with expert advice and infor-mation they need to pass the various com-munications exams given by the FederalCommunications Commission and othersponsoring organizations.

Authors Sam Wilson and Joseph A.Risse include important information on

dc and ac circuits and components, powerequipment, transmitters and receivers,digital basics, television systems, elec-tronic circuits and components, and manyother topics.

TAB/McGraw-Hill. Blue Ridge Summit, PA

17294-0850

Auto Audio: Choosing, Installing,Maintaining, and Repairing Car StereoSystems, By Andrew Yoder, McGraw-Hill, 352 pages, 200 illus., $34.95 hard-cover, $24.95 paperback.

Recent advances in automotive audioequipment have made an already com-plex subject even more mind -boggling.Today's components are far ahead ofthose available in the mid -1980s. With somany choices and options available, theaverage music -lover who just wants aquality car stereo system is often left con-fused about what to buy, and from whom.The first book to examine this subjectthoroughly, Auto Audio comes to the res-cue. This information -filled guide con-

tains practical, straightforward advice onhow to select and install audio systems,and provides tips and techniques formaintaining and repairing them.

Author Andrew Yoder begins by tellingreaders how to select an audio system thatsuits their individual needs. He coversinstallation procedures such as soldering,grounding, making electrical connec-tions, and running cables; and providesuseful tips for keeping a system in topcondition. Readers also will learn how toidentify and locate problems, and makesimple repairs. Other topics discussed indetail include: speakers and speakerenclosures, amplifiers, antennas, filtersand crossovers, wire, cabling, connec-tors, and transmission systems.

Technological breakthroughs in CDplayers, MiniDisc changers, DCC decks,and shortwave radio are also discussed.Finally, there is a lengthy compilation ofsources from which readers can purchaseproducts, supplies, and tools.

McGraw-Hill. Blue Ridge Summit. PA 17294-0850

LiteratureCatalog of advancedsoldering material

ESP Inc. has published a new 16 -page,full -color catalog describing its new Sol-der Plus soldering material, an advancedsoldering material designed to replacefluxcored wire, preforms and cut solder.

The catalog explains the material anddetails the benefits of this material inmany different applications, as well ascost advantages over solid solder. It alsoincludes pricing, technical data, orderinginformation, and full illustrations.

The material consists of microsizedparticles of solder alloy coated with flux.The outer flux coating helps it stick towherever it is applied, even on verticalsurfaces, and ensures proper fluxing ac-tion for reliable solder joints.

The solder is prepackaged in specialno -ooze syringes for manual or air pow-ered dispensing. The material allows ex-act deposit control, thereby reducing byup to 80% the amount of solder used.

Low-cost evaluation kits, also de-scribed in the catalog, are available thatinclude five 35 gram syringes, a reusable

hand dispenser and various dispensingneedles. Five alloys in four flux systemscover most electronic and electrical sol-dering applications. The product is safeand easy to handle, offers faster applica-tion and greater heating flexibility thansolid solder, and results in lower produc-tion costs.


Book catalogButterworth -Heinemann announces

the publication of its 1995 ElectronicsBook Catalog featuring new books in theEDN Series of Design Engineers, the Testand Measurement Series, and more.

The catalog includes something foreveryone. Whether you're looking for ahandy guide to the design of power sup-ply systems or a comprehensive hand-book on the IS09000 requirements,you'll find what you want in the catalog.

Books from the EDN Series includeSimplified Design of Linear Power Sup-plies by John D. Lenk, Power SupplyCookbook by Marty Brown, and Elec-tronic Circuit Design Ideas by Venkata-

raman Lakshminarayanan. From the Test& Measurement Series comes Building aSuccessful Board -Test Strategy byStephen E Scheiber.


Replacement components catalogThe latest issue of the Electronics Ware-

house Corporation's 188 -page quarterlycatalog, featuring more than 20,000 elec-tronic components, is now available. Thecompany supplies replacement parts toconsumer product maintenance organiza-tions and includes comprehensive cross-reference information for converting orig-inal manufacturers' part numbers intoreplacement types currently available.

Some of the major categories of prod-ucts offered include VCR belts, wheels,idler assemblies and tires, a section onsemiconductors, video game parts forNintendo and Sega/Genesis, and instruc-tional videotapes. Microwave parts, toolsand test equipment are also included inaddition to a commercial sound and secu-rity product section.



News (from page 4)

and housing discounts for people attend-ing the 1995 Electronic DistributionShow and Conference, April 19 through21 at the Las Vegas Hilton.

The Las Vegas Hilton is offering hous-ing for EDS attendees at a rate that is 15%lower than last year, $85.00 per night, sin-gle or double. For reservations, contactthe Las Vegas Hilton at 800-732-7117.Additional accommodations for EDSattendees are also available at CaesarsPalace. For reservations, contact Caesarsat 800-634-6661.

The Show Corporation has appointedDelta and United Airlines as official EDScarriers. Both Delta and United are offer-ing EDS attendees a 10% discount onunrestricted coach fares, and a 5% dis-count on any published fare. United,Delta, and most commercial airlines serv-ing Las Vegas, do not require a Saturdaystay over to qualify for discounted fares.

To make reservations on UnitedAirlines, call 800-521-4041, and indicateEDS '95 ID Number 591 WU. To makereservations on Delta Airlines, call 800-241-6760, and indicate EDS '95 FileNumber E0246.

In addition, Avis Rent-A-Car has beenselected as the official car rental agencyfor EDS '95. Contact Avis at 800-367-2847, and use Group Number A/B

622928 to obtain special EDS rates andany information.

The not for profit Electronic Dis-tribu-tion Show and Conference has been oper-ating since 1937, as the main event of theyear for the electronic distribution com-munity-distributors, their manufacturersuppliers, and the representatives whoprovide the year-round interface. EDS issponsored by the three major electronictrade associations focussing on distribu-tion: The Electronic Industries Associa-tion Components Group (EIA); TheNational Electronic Distribution Asso-ciation (NEDA); and the ElectronicRepresentatives Association (ERA).

For more information on EDS '95, con-tact the Electronic Industry Show Corp-oration, 222 S. Riverside Plaza, Suite2710, Chicago, IL 60606. Telephone:312-648-1140, Fax: 312-648-4282.

High -security system for 'MediaAccess' digital set -top boxes

Zenith Electronics Corporation andTeledyne are jointly developing a mili-tary -grade "crypto-graphic" security sys-tem for advanced cable and telephone net-works deploying video -on -demand,home shopping, video games and otherdigital services.

Teledyne, through its electronic systems

ES&T Calendar of Events

April 7-9, 19951995 Mobile Electronics Show (MES)

The Electronic Industries Association'sConsumer Electronics Group

Philadelphia, PA

April 19-21, 1995Electronic Distribution Show & conference

Las Vegas Hilton HotelLas Vegas, NV

May 17-18, 1995Systems Support Expo

World Trade CenterBoston, MA

10 am to 5 pm daily, 207-846-0657 Fax

May 19-20, 1995Electronics Technicians

Association annual conventionPhiladelphia Wireless Technical Institute

Philadelpha, PA

June 17 -June 19, 1995CES Specialty Audio &

Home Theater trade showI he Electronic Industries Association'

Consumer Electronics GroupChicago, IL

July 7-9, 1995The Fiber Optic Installers'

ConferenceRoyal Plaza Hotel

Marlboro, MA1 -800 -50 -FIBER,

Fax 1-617-241-8616

October 26-27, 1995Systems Support Expo

Moscone CenterSan Francisco, CA

10:00 am to 5:00 pm daily,207-846-0657 Fax

businesses, designs and implementsadvanced military identification systems.The agreement with Zenith is Teledyne'sfirst commercial venture involving mili-tary encryption technology. "We arepleased to forge this alliance with Zenith,"said Hudson B. Drake, senior vice presi-dent of Teledyne. "We view this as animportant step in establishing Teledyne asa provider of security technology to theemerging interactive multimedia market."

Using its patented cryptographic tech-nology, known as Dynamic SubstitutionDevices, Teledyne will create the ZenithDigital Conditional Access Module(DCAM) integrated circuit for use in the"Media Access" digital set -top decodersoffered by Zenith, Philips ConsumerElectronics and Compression Labs Inc.

"Teledyne's advanced encryptioncapabilities give Zenith set -top boxes amilitary -level security system that great-ly reduces the opportunities for piracy,which is a primary concern for cable oper-ators," said John W. Bowler, Zenith vicepresident, corporate R&D and networksystems engineering.

The Zenith -Teledyne DCAM integrat-ed circuit is a flexible, robust applicationspecific integrated circuit that will allowoperators system -wide control over ser-vice authorization to individual set -topboxes. It is also resistant to the most pow-erful cryptanalysis decoding to date andintroduces a new level of renewable set -top security to network operators.

"Our system should be as secure asthose Teledyne has designed for militaryapplication. As set -top decoders play asignificant role in the wide range of pro-gramming choices being developed, ahigh-level, tamper -proof security systemis essential. "Our Media -Access systemwill be the most secure on the market."

Teledyne's CDAM security cryptologyis compatible with the MPEG-2 world -standard decoder technology by Philipsand CLI, and Zenith's 16 -level VesitigialSideband (16-VSB) transmission, used inthe new Media Access set -top box. MediaAccess products will offer cable opera-tors a simplified interactive networkoperation and an enhanced ability toextend the services of third -party infor-mation providers into the network.

MPEG-2 and VSB are also key featuresof the Digital HDTV Grand Alliancehigh -definition television system.


ClassifiedClassified advertising is available by the word or per column inch.By -the word. $1.65 per word, per insertion, pre -paid Minimum charge is $35 per insertion. Initials and abbreviations count as full words. Indicate free category head-ing (For Sale, Business Opportunities, Miscellaneous, Wanted). Blind ads (replies sent to ES&T for forwarding) are $40 additional. No agency discounts are allowedfor classified advertising by the word. Contact Linda Romanello at 516-681-2922 to place your classified ad (by -the -word). Mastercard, VISA, American Express andDiscover are accepted for FAX or mail orders.Per column Inch (classified Display): $235 per column inch, per insertion, with frequency discounts available, 1" minimum, billed at 1/4" increments after that 10"maximum per ad. Blind ads are $40 addition. Reader Service Number $25 additional to cover processing and handling costs. (Free to 4 -inch or larger ads.) For moreinformation regarding classified display advertising please call 516-681-2922. Optional color (determined by magazine) $150 additional per insertion.

Send your order, materials and payments to:Electronic Servicing & Technology, 76 Non, Broadway, Hicksville, New York 11801 Attn: Linda Romanello

Phone: 516-681-2922 FAX: 516-681-2926

FOR SALE

**NewsFlash...TROUBLESHOOTING TIME DOWN -PROFITS UP!!Our NEW COMPUTERIZED TIP PROGRAM helps reduce your benchtroubleshooting time. The COMPUTERIZED TIP PROGRAM containsover 15,000 VALUABLE, TIME SAVING, MONEY MAKING TIPS!!!TVs, VCRs, CAMCORDERS & other electronics. PROFESSIONALBOARD LEVEL REPAIRS. ADD tips. PRINT tips. Owners of ourCOMPUTERIZED TIP PROGRAM say this is the **BEST** technicaltip program on the market today. Want to hear it for yourself? Talk toour customers and let them tell you how much they like our TIPPROGRAM. Works on ANY IBM compatible computer. The Price?Only $100.00 and NO COPY PROTECTION!!! (limited time only)Prepaid orders within the continental U.S.A. are shipped FREE.FREE Demo! FREE Phone Call! Have your own tips? Askabout our TIP EXCHANGE policy with FREE Updates! NEWSEXTRA: This is your last chance to order the amazing new com-puterized TIP program at this super low sale price. (The price goesup next month). Place your order NOW!!! CALL 1-800-215-5081.HIGHER INTELLIGENCE SOFTWARE, 60 Farmington Lane, Melville,NY 11747.

***SERVICE TIPS 1995 Version 3.02 IS HERESimple to use and not complicated, it organizes 16,068 SERVICETIPS in ALPHABETICAL ORDER by Brand Model/Chassis & Symptomwith 3 lines for Symptom and 8 for Solution. NOT ONLY CAN YOUREVISE and EDIT or PRINT any service tip in our database, but YOUCAN ADD YOUR OWN INFORMATION and it will automatically bealphabetized and sorted. Our program contains information from TECH-NICIANS like YOURSELF on TVs, Projection TVs, VCRs, Camcordersand other consumer electronic equipment. UNLIKE SOME OTHERPROGRAMS, WE HAVE NO GIMMICKS. SERVICE TIPS was designedand created by 2 CETs who are technicians/owners of their own servicecenters and a full-time programmer. SERVICE TIPS is available for$129.95 plus s&h. For more information CALL US at 1 -800 -621 -TIPS(621-8477) (from US & Canada). Demo Disk and Quarterly Updatesavailable. IF YOU USE WINDOWS, WE NOW HAVE AVAILABLE ASERVICE TIPS PROGRAM JUST FOR YOU. CALL US FOR MOREINFORMATION.

VHS -VCR Repair Solutions Sets I - IX. Each contains 150 symptoms andcures, free assistance, $19.95 each, all nine $49.95. Visa/MC. FAX (219)272-6612. Eagle Electronics, 52053 Locks Lane, Granger, IN 46530.

FOR THOSE SERVICERS WHO ARE NOT COMPUTERIZED ELEC-TRONIC SOFTWARE DEVELOPERS NOW HAS AVAILABLE FIVEIndividual Editions of SERVICE TIPS in Laser Book Form. Each indi-vidual book contains easy to read cures for those "extremely toughrepairs" on COLOR TVs & VCRs saving hours of troubleshooting time.The ZENITH Module Repair Book has 248 cures for Modules 9-124thru A-9740 for $29.95, EMERSON has 351 tips for $24.95, GOLDSTARhas 334 tips for $24.95, NEC has 164 tips for $19.95 & SANYO/FISH-ER has 455 tips for $29.95. ORDER ANYONE OR ALL 5 EDITIONSFOR $75.00 (a $54.75 SAVINGS). MAIL CHECK OR MONEY ORDERTO: ELECTRONIC SOFTWARE DEVELOPERS, INC. 826 So. Main St.,South Farmingdale, NY 11735.

FOR SALE

TV CASE HISTORIES: Booklet with 2,175+ histories. Satisfactionassured. Only $45 (plus $3.00 for priority mail). Mike's Repair Service,P.O. Box 217, Aberdeen Proving Ground, MD 21005. Same mailingaddress 31 years. Send SASE for samples. 410-272-4984, 11 am-9pm.

LOOKING FOR THE TV -MAN TECH -TIP PROGRAM?WE'RE NOW ON PAGE 25

YES, WE ARE LIKE THE BUNNY RABBIT THAT JUST, "KEEPS ONGOING."

FREE ZENITH CURESEarn $$$ Repair Zenith TV modules found in over 1000 models, 1983-1993. Symcure manual shows you how. $89.95 or send SASE for FREEsamples ZMEX, 807 Queen Palm Lane, Sarasota, FL 34243.

REDUCED 85%. Diehl Mark III $69, Diehl Mark V Horizontal circuittester $179. New. Conductive coating for remote control keypads $9.99ppd. WEEC, 2411 Nob Hill Road, Madison, WI 53713. 608-238-4629,608-233-9741.

SERVICE DATA & HARD TO FIND PARTS previously -owned SAMs,manufacturers data, books, FREE catalog. AG Tannenbaum, Box 110,E. Rockaway, NY 115' 8. 516-887-0057, Fax 516-599-6523.

STOP BUYING PARTS YOU DON'T NEED!Semiconductor cross for IBM and compatibles gives you a list of sub-stitutes for the part you don't have. Crosses transistors, ICs, diodes,SCRs and more! $39.95 Software Development Plus, South SideStation, PO Box 1376, Buffalo, NY 14205-1376.

SENCORE VG -91, TVA -92, SC3100, PR -57, CR-70. LIKE NEW. ALLLEADS AND MANUALS. 10KV AND 50KV PROBES, $7,000. 901-986-0410 after 5:00 pm.

MISCELLANEOUS

Wanted to do service center business part time. CET qualified. Ship tome UPS Consumer Electronics, 812-295-4240.

BUSINESS OPPORTUNITIES

TVNCR REPAIR 15 Yrs. reputation, only shop in town, beautifulKetchikan in S.E. Alaska. EVERYTHING for $40K. 907-225-2350.

TV -VCR Repair. St. Pete Florida, close to Beaches. Sencore equip-ment; parts and inventory, turn key operation, $15K. 813-546-8323.

Pacific Northwest repair shop for 30 years, same location. LicensedTEST EQUIPMENT BOUGHT & SOLD: OSCILLOSCOPES, ETC. 1-408- TV, stereo, microwaves, VCR, and computers. Completely equipped.738-4206. FAX 1-408-736-6946. Owner retiring. Susan -toward, IBA (503) 245-4464.


Readers' ExchangeReaders' Exchange has been reinstated as a free service.The following restrictions apply to Readers' Exchange: Only individual readers may use Readers' Exchange, and items must be restricted to those that are

ordinarily associated with consumer electronics as a business or hobby. If you're in business to sell theitem(s) you want to offer for sale, the appropriate place for your message is in a paid advertisement, notReaders' Exchange.

Readers' Exchange items must be restricted to no more than three items each for wanted and for sale,and may be no more than approximately four magazine column lines in length (about 20 words).

All submissions must be typed or printed clearly!Send your Readers' Exchange submissions to:

Readers' ExchangeElectronic Servicing & Technology, 76 N. Broadway, Hicksville, NY 1180 1

WANTED

Tentel HPG- I head protrusion gauge with S I stand.Also 23 and 40 channel CB radio performance testequipment. Contact: Pete, 701-663-5331 evenings.

Green Yoke pan number 330P09003 for Mitsubishiprojection TV Model VS -403R. Contact: W.C.Myre, 7306 Aztec Rd., Albuquerque, NM 87110.

Looking for schematic for TMK Model number1933 RC color TV Lafayette number LA84 amp.Precise Model 660 color generator Will copy andreturn or pay for copy. Contact: Gerard O'Gara,11 Crag La., Levittown, NY 11756, 516 -PEI -4075.

Service manual for Hitachi VHS Camcorder Modelnumber VM-1300A. This is a 9.6V model thatHitachi claims to have no knowledge of. Contact:Craig Rogers at Gunnison Electronic Repair, POBox 344, Gunnison, CO 81230. Phone/Fax/mes-sage at 970-641-1669.

Power transformer JVC part number A39982AYD.Contact: Bob Green, R.R. 1, Ridgetown, Ont.NOP2CO, Canada.

Knight, KG -688 audio generator, KG -686 RF gen-erator, and KG -687 sweep generator. All with man-uals. Contact: Charles T. Huth, 229 Melmore St.,Tiffin. OH 44883, 419-448-0007.

I need the operation manual and schematic for anOlson CRT analyzer Model TE-189. Will pay forcopy and postage. Call collect after 6PM EST 809-842-0019.

Service manual (used) for RCA CTC117 chassis,or Feb. 1986 issue of ES&T with CTC117 profax.Must be under $10.00. Contact: Craig at GunnisonElectronic Repair, Box 344, Gunnison, CO 81230,303-641-1669.

Power supply circuit board (stock number01243602) for Sansui VCR Model number S -V7.Contact: J. Powell, 299 Charleston Rd.,Willingboro, NJ 08046, 609-877-9143.

Service manual for Fisher FVH-830 VCR. Contact:Don Nitkin, 123 Coolidge Hwy., Birmingham, MI48009, 810-649-5012.

In need of schematic for BMC color monitor ModelNumber BM-AU9 191U. Contact: William Shiner,1608 Styer Dr., New Carlisle, OH 45344, 513-849-0577.

Need for parts radio clock Panasonic ModelRC6900C. Contact: Danny at 708-662-0165.

Schematic or service manual for Broksonic 5 inchcolor TV, AM/FM radio, Model Number CCRT3609. Contact: Paul Lombardi, 501 Jefferson Blvd.,Warwick, RI 02886, 1-800-437-3282.

Service manual or schematic wanted for a

Layfayette Neutrodine radio, Model K60. It wasmade around 1925-26. Contact: Chuck McGuire,PO Box 555, Jefferson City, TN 37760, or call 615-475-0335.

Sharp TV Yoke Number KYS-60159, Fisher motorassembly number 143-0-3404-03700, schematicfor Magnavox TV 13C202. Contact: Ed Herbert,410 N. 3rd St., Minersville, PA 17954.

Top, control panel glass for Frigidaire Flair range,Model Number RC I B6452. Contact: WarrenShukis, 1479 Prince Edward Way, Sunnyvale, CA94087, or call (days) 510-651-5112, (eves.) 408-739-2709.

Flyback transformer for RCA Model TC-127, chas-sis KCS34B, drawing No. 970975-1, part number274950. Will accept used, working unit. Contact:Mike Pickels, Sunset TV, 3131 Davie Blvd., Ft.Lauderdale, FL 33312, 305-583-5110 or Fax 305-581-8414.

FOR SALE

Sencore SC3080 oscilloscope, $1700.00; LC102 Zmeter, $1300.00, both for $2800.00. Units are inexcellent condition. Have probes, boxes, and man-uals. Also, Hitachi V 1060 dual -trace 100MHz.Oscilloscope $1700.00. Contact: Jeff 701-220-0049.

Heathkit, model AD -1013, audio oscilloscope withassembly maunual, $120.00. Contact Fred Stavans,142-11 248th Street. Rosedale, NY 11422 (718)528-9152.

Sentinel flutter meter, model FL -3D- I , $75.00;Leader AC microvolt meter, model LMV-89,$200.00; Sencore AM/FM stereo analyzer, modelSG I 65, $750.00. Contact: Mark (503) 888-4601home: (503) 267-0628 work.

Many radio and 1'V tubes for sale. Buy one or all.Send SASE for tube list. Contact: Mike McGary,1801 Mountainbrook Dr., Huntsville, AL 35801.

Thousabds of used TV/Radio tubes (all tested). Anytube $2.50 plus $2.00 shipping. Contact: W.F.Smith. 1054 S. Elizabeth, KoKomo, IN 46902.

Sencore, hardly used, still in original boxes: VA62,1,900.00; SC61, $1,500.00; VC93, $2,000,00. Alsofor sale: PR57, 500.00; TF46, $350.00; frequencycounter, $1,200.00. Offers accepted. Will sell sep-arately or together. Contact: Roy Harmon,Cleveland, OH (216) 234-3519.

Computer monitor schematics, all brands, alsoparts. Test equipment and parts. Contact: R.C.E.,P.O. Box 72882, Chattanooga, TN 37407, (706)866-3184.

Proton HVT KF5897FD, new, never used, $35.00(postage paid); RCA WR99A Marker generator,good condition, not used in years, $25.00 (postagepaid). Contact: (602) 296-5904.

Tentel gauges and tapes, very cared for condition.Package for only $975. Includes HPG-S, TQ-600,T2 -H7 -UM, TSH-V5, T.E.S.T. VHS, and TT2.Contact: Ron Schipinski, 3093 Carpenter Hills Lp,Lacey, WA 98503, (206) 438-3305.

Sams Photofacts, 650+, nearly complete from1500-2000 and 2334-2438. Also 32 folders highernumbers, $220.00; Micro -copy 10 corn microfichereader that also will make prints; like new, $200.00.Contact: John Mc Williamson, 4915 EdmonstonRd., Hyattsville, MD 20781, (301) 864-4164.

NRI VCR training course with video, $45.00; C-MOS IC tester, B&K, model 552, like new, $85.00.Also electronic books. Contact: Ralph Bianco,Boulevard TV & VCR Service, 1431 Robinson Ave.,Havertown, PA 19083, (610)446-4519.

Proton HVT, model KF5897, new, never used,$35.00 (postage paid); RCA Marker generator WR-99A, good condition, $30.00 (postage paid).Contact: Samuel M. Pearlman. 7513 D. Camino DeQuerabi, Tucson, AZ 85715.

Sencore Universal video analyzer, VC62, VC63,NT64, $1995.00. Comes with all cables and manu-als. Going out of business. Other test equipment forsale. Send SASE for list. Contact: Joe, Hc69, Box527-6, Parkhill, OK 74451, 1-(918) 457-4100.

B&K misc. pix-tube checkers, $50.00-$200.00;misc. high voltage probes, $20.00; B&K 10 meg dualtrace oscilloscope, model 1476, $150.00. Contact:Bill (503)267-0628 work: (503) 756-1725 home.

Sencore VC -93 VCR analyzer; SC -3100 100 MHzdual trace scope; CVA-94 camera analyzer withVR-940 color light box; VG -9I video generator;CR-70 beam builder CRT analyzer and restorer,includes all cords, test leads and instruction books.In original boxes. Assume balance, equipment 25%paid off. Contact Bob (801) 833-9320.

Sencore VA -48, $400.00; B&K 15 meg dual traceoscilloscope, model 1472C, $200.00; SencoreSC6 I, just serviced and updated, $1500.00.Contact: Audio Video Specialists, 892 So.Broadway, Coos Bay, OR 97420, (503)267-0628.

John F. Rider Perpetual Trouble Shooter's manu-als. Complete set, volumes 1-23. Excellent condi-tion. Best offer. Contact: Ed Rauchfuss, 946 SantaClara, Los Alamos, NM 87544, (505)662-2277.

One VA62 with front cover; VC63 head sub; andan NT64 pattern generator. All in perfect condition,$1200.00. Contact: (612) 874-8607.


Advertiser's Index

Company

ReaderPage Service Advertiser

Number Number Hotline

American Hakko Products 16 25 800/88 HAKKO

Andrews Electronics 11 26 800/289-0300

Chemtronics 5 48 800/645-5244

Electronic Technicians Assn 57 27 317/653-4301

Fluke Corporation BC 28 800/59 -FLUKE

Fox International 12 29 800/321-6993

H.C. Protek 49 46 201/767-7242

ISCET 57 817/921-9101

International Components Corp..67 30 800/645-9154

MCM Electronics 19 31 800/543-4330

McGraw Hill 61 800/822-8158

MICROCARE 17 2 800/638-0125

NESDA 12,48 800/433-5557

Parts Express 25 33 800/338-0531

Philips Technical Training 3 34 615/475-0044

Prelco 67 45 908/851-8600

Premium Parts + 16 800/558-9572

Sams, Howard & Company 14 35 800/428-7267

Sencore IFC,7 32,37..800/SENCORE

Sony Electronics 15 39

Sperry Tech 67 43 800/228-4338

Syncpulse 8 40 818/353-9595

TV Man Tech Tips, Inc. 25 44 800/474-3588

Tentel 18 41 800/538-6894

Thomson Consumer Elec....68, IBC 38

Tritronics, Inc 11 42 800/638-3328

We'd like to see your company listed here too. Call DianeKlusner at 516/681-2922 to work out an advertisingprogram tailored to suit your needs.

ELECTRONICSALES OFFICE

PHONE (516) 681-2922

FAX (516) 681-2926

ELECTE,

SPddNow :onto., eleettonieslechlkdoce,

TUBES .TUBES.TUBESWorld's Largest Range

Over 2,000 Types. Domestic & Foreign

UP TO 85% OFFAsk for

ice listpr

International Components CorporationT- Toll Free 800-645-9154 N.Y State 516-293-1500

1111 105 Maxess Road, Melville. New York 11747


Tech'sGuide

ToPrIci

S*

-Sperry Tech'sPricing Guide -Updated new 6th edition ...aframework for setting ratesthat apply to Hi -Tech pro-ducts ...a forrgula thatguarantees SUCCESS''Call Toll Free for details1-800-228-4338


cl.C.'S! TRANSISTORS!Largest selection of original RADIO, T.V. & VCRsemiconductors. Call or write for free catalog.

PRELCO ELECTRONICS DISTRIBUTOR605 CHESTNUT STREET UNION, N.J. 07083\JEL: 1-908-851-8600 FAX: 1-908-686-46561


To OrderBack Issues

Send S3.50 Per IssueCheck, Money Order,

Mastercard, VISA, Discoverand AMEX accepted

Send AllCorrespondence To:

Electronic Servicing& Technology76 North BroadwayHicksville, NY 11801

Or Call516-681-2922

FAX 516-681-2926Complete your collection today.

ORDER YOURBACK ISSUES

TODAY!


ALABAMACARMICHAEL ELECTRONICS INCDOTHAN AL 800-633-0911

ARIZONAARIZONA WHOLESALE SUPPLY COPHOENIX AZ 800-877-0771CALIFORNIAANDREWS ELECTRONICS INCSANTA CI. A RITA CA 800-289-0300Al! 0( A ECTRONICS SUPPLYSA \ I II 1 \ CISCO CA 800-652-1023CIII i h III [(LEY'S ELECTRONICS INCSA( Et 1 \ I 1 vro CA 800-655-4004IN I i )1 I .ECTRONIC SUPPLIERS1111;111 \ CA 800-833-9254INLAND ELECTRONICS SUPPLIERSMODESTO CA 800-692-5788INLAND ELECTRONICS SUPPLIERSSAN JOSE CA 800-262-1130JACK C ARBUCKLE COBAKERSFIELD CA 805-325-5816JACK C ARBUCKLE COFRESNO CA 209-264-6554MARTIN DISTRIBUTING COHUNTINGTON PARK CA 800-660-8771FLORIDAC&S ELECTRONIC SUPPLY CO.ORLANDO FL 800-321-6993DOW ELECTRONICS INCJACkso \ \ I I.: 800-627-2870Ill F IJ(1.I Il0AICS INC010 \\I)(1 FL 8(10-627-2950DM\ ELECTRONICS INCTA MI' \ El. 800-627-2900F!)! It AKERS ELECTRONICS INCT \11ASSEE El. 800-635-042011Eli \ 1 AN ELECTRONICS\ 11 \ \ II FL 800-938-4376RES MARKETING INCTAMPA Fl. 800-444-7304TRITRONICS INCFT LAUDERDALE FL 800-365-8030VANCE BALDWIN INCFT LAUDERDALE FL. 800-432-8542VANCE BALDWIN INCMIAMI FL. 800-432-8542VANCE BALDWIN INCTAMPA Fl. 800-299-1007VANCE BALDWIN INCWEST PALM BEACH 11. 81X1-367-1641

GEORGIADOW ELECTRONICS INCALBANY GA 800-627-2810DOW ELECTRONICS INCNORCROSS GA 800-627-2810DOW ELECTRONICS INCSAVANNAH GA 800-627-2890FOURAKERS ELECTRONICS INCMACON GA 800-554-4347FOURAKERS ELECTRONICS INCVALDOSTA GA 800-422-2801WHOLESALE INDUSTRIAL. ELECTRONICSNORCROSS GA 800-282-1857ILLINOISDEITRONICS DISTRIBUTING COBEI 1 \ II .1 E II. 618-236-0366Hifi\ \ R D I I.FI . FIIONICCHICAGO IL 312-254-9091KLAUS RADIO INCPEORIA II. 800-475-5287LACO ELECTRONICS INCDECATUR II. 217-423-0494LACO ELECTRONICS INCMT VERNON IL 800-642-4901TRI-STATE ELECTRONIC CORPMOUNT PROSPECT IL 800-445-0896UNION ELECTRONICS INCSOUTH HOLLAND IL 8(X)-648-6657INDIANAESP/ELECTRONIC SERVICE PARTSINDIANAPOLIS IN 800-382-9976IOWAGIFFORD-BROWN INCDES MOINES IA 8110-369-4433KANSASA(: \I V II 1 1)10 SUPPLY COTOPE!, \ KS 800-544-8521MA N11 \111N ELECTRONICS CORP0\ \ NO PARK KS 800-821-3114KENTUCKYRADIO ELECTRONIC EQUIPMENT COLEXINGTON KY 606-255-6661RANDOLPH & WARRENLOUISVILLE KY 800-765-7278RANDOLPH. HAI.E & MEREDITH INCBOWLING GREEN KY 502-781-1460LOUISIANASOUTHERN ELECTRONICS INCSHREVEPORT I.A 800-521-4391MASSACHUSETTSE A ROSS CO INCFALL. RIVER MA 800-828-4901

Skis JIISr.

Tties

FOR VCRsAND

CAMCORDERS

HEADS

Aft111":"

Call yourThomson

Distributorfor your freecopy today!

LERS

KITS

THOMSON CONSUMERELECTRONICS

ELECTRONIC DISTRIBUTORS CORPNORTH QUINCY MA 617-328-7800NASH ELECTRONIC SUPPLY INCLEOMINSTER MA 508-537-0707TEE-VEK SUPPLY COMPANY INCMEDFORD MA 800-255-5854

MARYLANDFAIRWAY ELECTRONICS INCHAGERSTOWN MD 800-654-5052

FAIRWAY ELECTRONICS INCKENSINGTON MD 800-352-1474TRITRONICS INCABINGDON MD 80(1-638-3328

MICHIGANBURSMA ELECTRONIC DIST. INC.BENTON HARBOR MI 800-777-6261

BURSMA ELECTRONIC DIST. INC.GRAND RAPIDS MI 800-777-2604

BURSMA ELECTRONIC DIST. INC.TRAVERSE CITY MI 800-777-6261ELECTRON IC PARTS SPECI A LISTFLINT MI 810-238-7311REMCOR ELECTRONICS INCOAK PARK MI R00-482-2133

MINNESOTANESS ELECTRONICS INCMINNEAPOLIS MN 800-247-1318PACE. ELECTRONICS INCROCHESTER MN /CO -444-7223

MISSOURICENTRAL MISSOURI DISTRIBUTING COJEFFERSON CITY MO 314-636-3149

CITITRONIX INCST LOUIS MO 800-M6-2484

DELTRONICS DISTRIBUTINGST LOUIS MO 800-443-0665

MISSISSIPPIN & II ELECTRONICSII AITIESBURG MS 800-264-8808

NEBRASKASCOTT ELECTRONIC SUPPLY CORPLINCOLN NE 800-333-7952

SCOW ELECTRONIC SUPPLY CORPOMAHA NE 800-333-7953

NEW JERSEYLINWOOD WHOLESALE INCWALL TOWNSHIP NJ 800-326-0313

GQuality Universal Video Parts.

The only way we can make your business our business is to grow in yourdirection. That's why we've expanded our product line to include the videoand camcorder parts that take more wear and tear than other parts. And,we've done it at such a minimal cost, these quality parts have genericpricing. Plus, our new product line is so inexpensive, yet so efficient, itallows you to turn your job estimates into jobs completed. The SKUniversal Line, it's quality without the cost.Now for a limited time, you can get our complimentary Cross Reference.This cross-reference guide was designed by a professional serviceman, toaccurately help you find the right part. Just one more way ThomsonConsumer Electronics is making life a little easier. Call your TCEdistributor today.

Parts That Are Easy To Order -Just ask your TCE Distributor.

Parts That Come With An Easy -To -Use Cross Reference.

Parts That Have Quality Without The Cost.

Use SK Universal Parts With Confidence.

THOMSON CONSUMER ELECTRONICS, INC.

I'ANSON ELECTRONICSPINE 1310)0K NJ 800-255-522'

NEW MEXICOIi & R ELEcritomc SUPPLY C11IOBBS NM 505-393-1613

NEW YORKEIGER ELECTRONICS INCDEER PARK NY 800-835-8316GMB SALESFARMINGDALE NY 800-874- 1 765RADIO EQUIPMENT CORPBUFFALO NY 716-874-2690STANDARD ELECTRONICS INC

MHERST NY 800-333-1519STANDARD ELECTRONICS INCSYRACUSE NY 800-333-1639

NORTH CAROLINAsouTHEASTERN EI.EC SUB/CA M BARFAY ErrEvILLE N(: 800-682-3670

THEASTERN ELEC SUB/CAMBARIi \ .EIGH. NC 800-682-5707

()I110E \ :El. DISTRIBUTING INCCINCINNATI OH 800-733-3329

FOX INTERNATIONAL. ETD INCBEDFORD HIS OH 8010-321-6993

MCM ELECTRONICSMORAINE. OH 80-543-4330

SUPERIOR ELECTRONIC PARTS CO INt.PARMA OH 800-875-7942

OKLAHOMARADIO SUPPLY INCOKLAHOMA CITY OK 800-522-3821

OREGONDOUBLE. 0) ELECTRONICS visTR IN(:PORTLAND OR 800-452-7688

PENNSYLVANIACLEARFIELD ELEcrimNic SUPP C()HYDE PA 800-635-0325

CRS ELECTRONICSPITTSBURGH PA 412-431-77010

I:1: MBERI. NN D ELECTRONICS INCARRISlit 10: PA 800-922-2271

I NI \ ND ELECTRONICS INC\ \ \ I I li PA 800-242-3703

CUMBERLAND ELECTRONICS INCYORK PA 800-632-9025H B F ELECTRONICS INCPHILADELPHIA PA 800-426-4230LINWOOD WHOLESALE INCMARCUS HOOK PA 800-326-0313

SOUTH CAROLINAHARLEY'S WHOLESALE ELECTRONICSSPARTANBURG SC 800-326-7961

WHOLESALE INDUSTRIAL ELECTRONICSCHARLESTON SC 800-868-2211

WHOLESALE INDUSTRIAL ELECTRONICSCOLUMBIA SC 800-868-2213WHOLESALE INDUSTRIAL ELECTRONICSGREENVILLE SC 800-868-2215

TENNESSEEELECTROTEX TENNESSEE INCMEMPHIS TN 800-460-1808RAND( )1 III II \ LE & MATTHEWS INCCLARK-- \ II FN 800-227-8652

NI (.1 C6E15-I N2C55-5601

RNAASNIII)k"III 11'111 \I

SHIELDS F:11 moNICS SUPPLY INCBRISTOL -1 \ 800-325-0007

SHIELDS ELECTRONICS SUPPLY INCCHATTANOOGA TN 800-508-0733SHIELDS ELECTRONICS SUPPLY INCKNOX VII.I.E TN 800-235-7615TOWNSEND ELECTRONIC SUPPLYJACKSON TN 800-926-8726

TEXAS1.1.0 WHOLESALE ELECTRONICS INC

I I \t (MTH TX 817-877-5854\ 8.1.0 WHOLESALE ELECTRONICS INCII: \ I NG TX 800-488-2782

I :TROTEX INC AIRLINESTON TX 800-275-7801:TROTEX INC AUSTIN

IIN TX 800-460-1806ELEC'TROTEX INC BEAUMONTBEAUMONT TX 800-460-1803ELECTROTEX INC CORPUS CHRISTICORPUS CHRISTI TX 800-460-18051 I ICTROTEX INC DALLAS

\ LLAS TX 800-460-1807ELECTROTEX INC RICHMOND1101.STON TX 800-460-1801I I ECTROTEX INC WINKLER

STON TX 800-275-78011 1. ( TROTEX INC SAN ANTONIO\ \ ANTONIO TX 800-460-1804

INTERSTATE ELECTRIC CODALLAS TX 800-527-4(r29R & R ELECTRONIC SUPPLY COABILENE. TX 915-677-2974B & R ELECTRONIC SUPPLY COAMARILLO TX 800-300-7991

& Ii 11 ECTRONIC SUPPLY CODALL \- IA 915-566-9693

& It I I ECTRONIC SUPPLY COELI' \ IX 915-566-9693R & 1(1 I.EcTRoNic SUPPLY COLUBB0ch TX 800-299-7000R & R ELECTRONIC SUPPLY COODESSA TX 915-332-9167WILTRONICS SUPPLY INCPARIS TX 800-426-6317WILTRONICS SUPPLY INCTYLER TX 800-6.57-2404

UTAHBALLARD SUPPLY CORPORATIONSALT LAKE CITY UT IMO -662-8561

WEST VIRGINIAELECTRONIC SUPPIN INCHUNTINGTON WV 303-523-6443

WISCONSINC M POPKEY COGREEN BAY WI 800-444-5920G M POPKEY COMADISON WI 800-444-532()

M POPKEY CONEW BERLIN WI 800-444-9320CMPOI'KEYCOWAUSAU WI 800-444-7920TAYLOR ELECTRIC COMEQUON WI 8OO-558-6970

Nol all 81)0(fs are inierstale.


The newIntroducing a whole new category of handheld instruments: the new 860

Series GraphicalTM MuftiMeters (GMM) from Fluke. GMM' test tools pair

the world's most advanced multimeter capabilities with graphical display

power. You choose what information you want to see, and how you want

to see it. All by turning the simple, multimeter-style rotary knob and

pressing the Display Mode button. It'll feel so familiar, yet what you'll see

is brand new.

Turn the knob to the function you want, press Display Mode to select

waveform display, and you'll see noise, waveform distortion, and intermittent

failures - or capture glitches - automatically.

GraphicalUse In -Circuit Component Test to look at component signatures in -circuit,

without risking damage to sensitive components. Or let the GMM test tool

monitor a test set up, plotting meter readings for up to 30 hours with theTrendGraph" Display Mode.

With the 860 Series, you'll be using the most accurate handheld meter

ever made - 0.025% basic dc accuracy and a 32,000 -count (more than4-2/3 digit) display. All functions offer true IEC 1010-1 Class III 1000V

protection. Plus the most comprehensive set of muftimeter functions

(including capacitance and dB) in a handheld meter. The Dual Display

(primary and secondary numeric readings) along with the Analog

NeedleGraph" display, lets you see frequency, pulse width, or duty cycle.

And you don't have to buy special test leads; one simple setof meter leads supports every function of the fully integrated860 Series.

GMM test tools start at $795. For a graphic demonstration,see your local FLUKE distributor or call1 -800 -59 -FLUKE for directconnection to a distributornear you. For immediatefax -hack of 860 Series literature.call 1 -800 -86 -FLUKE.

© 1994 Fluke Corporation. P.O. Box 9090. M/S 250E, Everett, WA,USA 982069090. U.S.: (800)44 -FLUKE or (206) 356-5400. Canada (905) 890-7600.Europe (31 40) 644200. Other countries (206) 356-5500.All rights reserved. Ad No. 00698.

Serious Tools for Serious Work.

FLUKECircle (28) on Reply Card

THE PROFESSIONAL MAGAZINE FOR ELECTRONICS AND … · 2019. 7. 17. · SmarTips Locate Philips...

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Transcript of THE PROFESSIONAL MAGAZINE FOR ELECTRONICS AND … · 2019. 7. 17. · SmarTips Locate Philips...