Tektronix service manual O o, A o, 494A/494APServiceVot.1

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494A/494APServiceVot.1

PREFACE

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This manual contains servic€ informationfor the TEKTRONfX494A1494ApThe. informationis tocatedin two volumes.Volume1 containsthe text andVolume2 containsthe diagrams and parts lists. The Tabte of Contents in each volume lists the contents of both volumes.

Manualsthat describeother aspectsof the product are:

. Operator'sManual

. Operator'sHandbook

o Programmer'sManual

o Programmer'sReferenceGuide

Who Should Use This Manual?

This rnanualis intendedfor electronictechnicians with experiencein servicingdigital,analog,andrf circu- itw. Circuit analysis is mostly functionil and shoutd help isolatemost malfunctioneto a board or block of circuitry.The technicianshouldthen be abte,with the aid of test equipment,to isolatethe malfunctionto a specificcomponentor components.

This instrumentcontainsfirmwarethat providesa thoroughinstrumentcheck duringpowerup and during operation,and if needed,guidesthe usei throughai abbreviatedfront-panelcalibrationprocedure. lf cali_ brationcannotbe achieved,a diagnostictest detects and isolatesmost problemsto the system,suchas 1st LO. The techniciancan then run troubleshootingdiag- nosticsto further isolate the problemto the board or

blockof componentsRefer. to theMaintenancesection for diagnosticsinformation.

DocumentationStandards

Most terminologyand graphicsfollow ANSI stan_ qalds. A glossaryof terms is providedas an appendix. Referto thefollowingstandards:

. ANSIY1.1- Abbreviations

. ANSIY32.2- GraphicSymbots

o IEEE91 - LogicSymbots

Change/HistoryInformation

Sometimesinstrumentchangesoccur or manual errors are found that make some of the informationin the manualinaccurate.When that happens,Manual ChangeInformationnoticesare insertedat the rear of the manual.Thishelpsensurethatthe manualcontains the latestandmostaccurateinformationavailablewhen the productis sold.

History information, with the updated data, is integratedinto the text or diagrams: Whena text page is updated,the revisedpages are identifiedby a revi- siondate in the lowerinsidecornerof the page. When a diagramis updated,the revisiondate is placedat the

lower center of the diagram. History informationis shown with a gray tint. When a componentvalue is changed,the designatoron the drawingis boxedwitha grey outline. Whena circuitis deletedor changed,the originalconfigurationis shownin grey, drawn eitherat its originallocationor to the sideof the drawing.

lf you havea manualotherthanthe one that came with your instrumentit maycontainrevisionsthatdo not applyto your instrument;however all historyinforma- tion that pertainsto the earlierinstrumentsis retained. When a major modificationhas been made to an assemblyor circuit board,the data for the replaced assernblywill follow the new informationand will be identifiedwith appropriatetitles or headingssuchas instrurnentserial number range or the assemblyor boardpart numbers.

Also, if your instrumenthas an assemblyreplaced with a newer version,documentationfor the newer assemblymay be supplied. Contactany TektronixSer- viceCenterfor information.