Tektronix 494AP service manual Corrective Maintenance, Maintenance- 494Al4g4fupService Vof

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Maintenance- 494Al4g4fupServiceVof. 1

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CORRECTIVE

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MAINTENANCE

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Corrective maintenanceconsists

of

component

Tel(ronix iepair centers provide

,replacement

replacement

and instrumentrepair. Speciattecnhiques

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and procedures that

to-remove and

repairserviceon maior assembliesas well as the unit.

replace assomblies may be iequirJj

Returnthe instrumentor assemblyto your local Field

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and/br

"ompon"nis in

tnis instru-

Officefor this seMce, or contact your l6cat Field Oftce

msntare describedhere.

for repairand exchangerates.

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Handling Static Sensitive Components

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Firmware Version and Error Message Readout

Most semiconductor..types,

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assembliEs,

both separatetyand in

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are susceptible

see Table

to damageto statii charge,

This feature provides readout of the firmware

ver_

6-1 for voltage

levels. WJrecommend

sensitiveprocedures be implemented

static

sion whenthe poweron/off is cycled. Duringthe initial

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for att operations

power-upcycle,the instrumentfirmwareandiront panel

involvingsemiconductorhandling.

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firmwar€ versionsare displayedon the crt for approxi_

Obtalning Replacement parts

matelytwo seconds. The ReplaceabteElectricalparts

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list section,under Memoryboard (A54),

All electrical and mechanicalparts are available

lists the ROM

devices and their Tektronix part'numbers for

each

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throughyour locatTektronix

oi'r"pr"r"nt"-

firmwareversion.

Fielddffic;

tive. The Replaceabteparts rist sectioncontainsinfor-

Wheneveran error occurs in an operationalroutine,

C

mationon how to order these replacementparts.

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an eror message on screen describesthe nature of

the error. Statusmessagesor prompts(seeDiagnosi-

t

tics part of this section),are also displayedwhen run-

ninga diagnostictest or calibrationproceiure.

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Some componentsthat are heat sinkedto

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the circuit board extrusion

or modulewall,

Selected Components

are soldered to the board after the board is

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mounted in

place. This is necessary to

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avoid crackingthe casewhenthe mounting

A few components

lgrew ls tightened. Thesecomponentsare

parameters

that are selectedto meetcertain

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identifiedby a note on the schematicdraw-

such as temperaturecompensation,

or to

ilg.

part

center the range of some adjustablecomponent. The

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.Their

number appears

with

selected componentsare identifiedas selectableon

chassis

mounted

componenis

in

the

the circuit diagram and in the ReplaceableElectrical

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ReplaceableElectricalpartslist.

Partslist.

parts

list descriptionfor the

The Replaceable

Parts orientationand lead dress should be dupli_

componentgiveseithera nominalvatue.The procedure

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for selection is explainedin the adjustmentpart of

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cated because

some components are oriented to

recalibrationprocedure. Table 6-4 lists these com-

reduce interaction between circuits or

control circuit

ponents,their nominalvalues,and the criteriafor selec_

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characteristics.

tion.

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Where applicable,an improvedpart will b€ substi_

tuted.whena replacementis ordered. tf

the changeis

Replacing EPROM or ROM Devtces

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complex, your local Field Office or representativewill

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contact you concerningthe change. After repair,the

circuitsmay needrecalibration.

Firmware for

the microcomputeris containedin

a

ROMpacks on the Memoryand GplB boards. Referto

Parts Repair and Return program

the ReplaceableElectricalparts list (vot.2) underthese

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assemblies(A54 Memory

and A56 GplB) for the ver-

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Assembliescontaininghybridcircuitsor substrates

sions and integrated circuit

part

numbers. All

in a semi-sealedmodule,and

complexassemblies

integrat€d circuits are soldered into sockets on the

C

as ths 1st LO, 829 MHz conv€rter,

such

boardto reduceproblemsthat occur due to poor con-

or phasegatectetec-

tact becaus€ of

corrosion

or

loose pins. Refer to

tor, can be returnedto Tektronixfor repair under the

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repairand returnprogram.

replacing Transistor and Integrated Circuit for

pro-

cedure.

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6-1s

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