Tektronix 494AP service manual A o o o a o o a o o o o o o o o o o o o, Filrcsotocr

Adjustment Procedure- 494[l4g4Ap ServiceVot. 1

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6097-18

Figurc 5-14. Test equipment3etuptor adiustingtlre VarlableRe3olutionrnoOut".

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v.Check LIN disptay linearity by adding 6 dB,

12dB. and 18 dB of attenuationand note the display step down from full screento, 4 +0.4, 6 *0.4, and 7 *0.4 divisions.

w.Remove the signal generator from the Log Amplifierinputjack and reptacep621. Reptacep3035 on the Video Processorboard.

8.Adjust ResolutionBandwidth

and ShapeFactor

(c304r, c5048, C505s, R106s, R3015,R3029,

R3033,and R4025on the VR 2nd FilterSetect

board)

(c1034, C1044, C1046, C2030, C3O3O, C3039, C3045, and R1027 on the VR 1st Fitter Setect board)

(c1032, C4015, G4028, C4036, C4045, C4051, C4060, R3010, and R3025 in the 10 Hz Fitter Assembly)

(R2025 on the 10 dB Gain Steps board)

The 3 dB down bandwidth of each filter section should be as wide or slighfly wider than the 6 dB down point of the combined two filter sections.

The filters in each section are aligned separately,then a signalis appliedthrough both the first and second sections. The final adjustments trim filter shape and bandwidth. Because of interaction,it is easy to offset one filter to compensatefor another misadjustedfilter; therefore,only adjusteachfilterin smallincrements.

Before calibrating the Variable Resolution Bandwidth and Gain, disable use of cal factors by pressing <Blue-SHIFT> PULSE STRETCHERand selectingitem5, thenitem 0.

a.Equipmentsetupis shownin Figure5-14.

(1)Remove and install the Variable Resolution moduleon an extender.

(2)Usea Sealectromale-to-maleadapteranclcoax- ial cable to connect the 10 MHz lF output signal, from the 3rd Converter,to the input of the second s€ction (makeconnectionfrom plug removedfrom J693to J683).

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5-14

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