Tektronix 494AP O a o O o o o o o o o o, O o o o o o o o o o o o o o o o o o o o o o

Adjustnent Procedure- 4g4A/4g4ApServtceVot. 1

Figure 5-9. Sweep board tlming adiustment and test point locations.

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The SpectrumAnalyzerhas a procedurein firmware for calibratingthe frequencycontrolsystem. However, it is possiblethat some adjustmentsmay be misad_ justedenoughto causethe microcomputerio displayan

€rror message. lf this occurs, bypassthe step then returnto the calibratlonroutine.

Test equipment required for this step are a Voltmeter, Time Mark Generator, and Fiequency Counter.Set the followingSpectrumAnalyzercontrols:

FREQUENCY 0.0 MHz

FREQSPAN/DV 5 MHz

TRIGGERING FREERUN

b.Connecta shortingstrap from Tplogs. on the SpanAttenuatorboard,to chassisground(Figure5-10).MonitorTP1073on the SpanAttenuatorboardwith the voltmeter.

---c:Adjust Sweep Offset R1063 (Figure S-10) for 0.00v.

d.Removethe shortingstrap from Tp1035. press <BIUe.SHIFT>PULSESTRETGHERand selectitem 1 (FREOUENCYLOOPS CAL), then item 0 (OVERALL SYSTEM)from the menus. perform the calibration steps as directed('CONNECTA DVM TO Tp105gON THE1STLO DRTVERBOARDANDGROUND,),etc.

(1)lf a "CALBRATIONSTEPCANNOTBE COM- PLETED"messageis displayed,bypass the step, perform the other adjustmentsthen return to the adjustmentand try to bringthe adjustmentin range. lf the problempersists,referto Troubleshootingthe FrequencyControlSystem,in the Maintenancesec_ tion.

e. Adjust1st LO Sweepas follows:

(1)Applythe CAL OUTsignalto the RF tNpUT,set the FREQUENCYto 600 MHz, FREQ SPAN/DIVto 100MHz, and set the REF LEVEL to displaythe mark€rs,

(2)Adjust'TuneCoil Swp R1065,on the Span Attenuatorboard (Figure5-10)for one markerper divisionover the center eight divisionsof the grati- cule. Reset the CENTERFREQUENCYas neces- sary to alignthe markers.

(3)Removethe Calibratorsignal and apply0.2ps time marksfrom the Time Mark Generatorto th€ RF INPUT.

(4)Set the FREQSpAN/Dtv to 5 MHz, REFLEVEL to +10 dBm,and FREQUENCYto about10 MHz.

(5)Adjustthe lst LO FM Coil Swp R1071(Figure 5-10)for 1 marker/divisionoverthe centereightdivi- sionsof the display.

(6)Set th€ FREQ SPAN/DIVto 20 KHz and appty 50 ps markersfrom the Time Mark Generator.

nAdjust the 2nd LO Sweep, R1067, for one marker/divisionoverthe centereightdivisions.

f. AdjustDot Markerpositionas follows:

(1)Press<Blue-SHIFT>RESET.

(2)AdjustDot PositionR1052on the Sweepboard to positionthe dot markeroverthe start spur.

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