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AdiustmentProcedure- 494A1494ApService Vol. 1

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Figure5-18.Adiustmentson the 10 Hzl100Hz Bandpass
Filter assembly.
	Table5-3
	FILTER
	Filter	Locatlon
	1 MHz	Figure5-17
	10 kHz	Figure5-17
	1 kHz	Figure5-17
	1 0 0 H z	Figure5-17
	1 0 H z	Figure5-15

5 - 18

9.Preset the Variable Resolution Gain

and Band Leveling

(R1030on the PostVR Amplifierboard) (R2031on the Va #2 Motherboard). (R3035on the 10 dB GainStepsboard) (R2023and R2060on the 20 dB GainStepsboard)

The Log Amplifiermustbe calibratedbefore adjustingany VariableResolutiongain set- tings. Log Amplifier calibration can be verifiedby applyinga +6 dBm, 10 MHz sig- nal to the input(J621),of the Log Amplifier, and checkinglor full screendisplaywiththe REFLEVELat -20dBM.

a.Before adjustingthe Variable Resolutiongain and band leveling,set the correctionfactorsto zero by pressing <Blue-SHIFT> PULSE STRETCHER,and selectingmenuitem5, thenitem2.

b.Test equipmentsetup is shown in Figure5-14. Set the SpectrumAnalyzercontrolsas follows:

FREQSPAN/DV	1 MHz
RESOLUTIONBANDWIDTH 100 kHz
REFLEVEL	-20 dBm
MIN RF ATTEN	0 d B
VERTICALDISPLAY	2 dB/DrV

c.The gain of the Post VR Amplifiershould be 20 dB for best signal-to-noiseratiothroughthe Variable Resolutionstages. lf any maintenancehas been per- formedon this stage,performthe followingsteps.

(1)Removethe cover for the VR 2nd Filter Select board. Disconnectthe jumper connectorto the inputof the PostVR Amplifier(pinJJ).

'10 -14 dBm signal,from a 50o

(2) Apply a MHz,

signalsource,to pin JJ of the amplifier.

(3)Adjust Post VR Gain R1030 on the Post VR Amplifierboardfor a full screendisplay.

(4)Removethe signaltrom the inputto the PostVR

Amplifier and replace the iumper connectorto pins

JJat the input to the Post VR Amplifier. Replace the coverfor the VR 2ndFilterSelectboard'

d.Set the front panelAMPLCALfullycounterclock- wise and set the Band 1 Galn R20310n VR Mother baard#2 (Figure5-15)fullycounterclockwise.

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