Tektronix 494AP =?l, RPlo3s-.8, Adjust Log Amptitier, R1012 R102S,R1030, LogAmptifier Board

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Adjustment

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494Ll4g4Ap

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Procedure

ServlceVol.1

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TuneCoil

R1065:ttl

FM Coil Swcco RtOZl

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rPlo3s-.8

=?l

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Span Attcnualor

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boild

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\circgir

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Ccnter Frcqucncy

controlboord

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lst LO Orivct

lcircuit board

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II

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R1031Rro32 R10:t4

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556G17

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Figure5'10.Frequencycontror

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systemtest potntand adiustmentrocations.

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7. Adjust Log Amptitier

c. Centerthe two front panel LOG and AMPL CAL

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(R1012,

R102S,R1030,

adjustments. Set the signat generatorcontrolsfor a

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LogAmptifier

board)

10MHzl+6 dBm output.

Set the step attenuatorsfor

50 dB of attenuation.

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d. Positionthe displayat a graticulereferenceline

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with the verticalPOSITIONcontrol,

thenswitchthe REF

Use only an

insulatedscrewdriver

LEVELfrom -60dBm to -110dBm in decadesteps.

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or tuning

tool to maketheseadjustments.

e. S€t the front-panelLOG CAL such that each

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10dB stepequalsonedivision.

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. a. Set the Log Amplifiercorrectionfactorsto zero

f. Resetthe REF LEVEL

-20

dBm and tha step

b_y pressing (Bfue-SHtFT>

PULSE STRETCHER

attenuatorsfor

to

0 dB attenuation.Resetverticalposition

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(DIAGNOSTIC

FUNCTTONS;

to a graticule

(DISABLE/ENABLE

and setecting

item 5

lineif necessary.

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USE

OF CAL FACTORS),

tnen item

g.

Increase the

attenuation through the step

2 (SET RESULTSTO "UNCALED). RemoveLeveler

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attenuators

Disableplug P3035on the Videoprocessorboard(Fig_

in 10dB increments

to 50 dB.

ure5-11).

_ h- Adjustthe Log Gain,R1037(FigureS-13)so each

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b. Connectthe t€st equipment

10 dB incrementof attenuation

resultsin onemajordivi-

as shown in Figure

sionof changeon thEdisplay.

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5-12. (P621must be removedin order to accessJ621

on the Log Amplifierboard. See FigureS_1g.)Set the

. i. Reset verticalposition by temporarilyremoving

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SpectrumAnalyzercontrolsas follovis:

the signaland settingthe verticatPOSITIONcontrolto

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position the baseline at the bottom graticule line.

FREQUENCY

2MHz

Returnthe step attenuatorto 0 dB. Displayshouldbe

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FREOSPAN/DV

2MHz

full screen (+6 dBm); if not, readjustJtrg*iglfial-gene@-

AUTORESOLN

On

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lzJ,r rli,1 [v

i:"lllCrerh

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REFLEVEL

-60 ctam

for

j. AdjustInputReferenceLevel,R1012(Figure5-13)

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MIN RF AfiEN

OdB

minimumamplitudechangebetweenthe 10 dB/DlV

VERTCAL

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DTSPLAY 1OdB/DtV

and 2 dB/DlV displayswhile alternatelyswitchingthe

TtMEiDtV

10 ms

VERTICALDISPLAY

between10 dB/DtVand 2 dB/DlV.

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5 - 11

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