Tektronix 494AP service manual O o a o o o o o o o a o o o a o

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		Adjustment Procedure- 4g4A/4g4Ap
		ServiceVol. 1
ffwu"nffEneilercYEl		R10f2
		LOGFIOELTTYR1O6O
	REFERENCELEVEL RIOIIO
	n	Lqrc^$t*FroilT
@ftftfl		Pl075
ll
		(J620)

filloll	Pm70
	(J621)
	L-HHF
l--E	il
L-.,E
il

Figure5'13.Log and video Ampri{iertest porntand adiustmentrocations.

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.- .k. lctlvate 2 dB/Dtv and add 10 dB of artenuation. lf..the1098 step (S division)is short,adjustthe gain slightlywith R'037in the same direction;'thenrem-ovethe 10 dB of externalattenuationand adjust R1012for a full.screendisplay.Repeatthis checkuntitthe 10 dB step is within0.2 dB of 1OdB. Activate10 dB/OtVand recheck10dB logging.

. l: Activate2 dB/Dlv and momentarilyremove the input signalto the Log Amplifier. positionthe baseline on the bottomgraticulelinethen returnthe signalto the Log Amplifier.

_ 11 Adjust Output-ReferenceLevel,R1030 (Figure 5-13)for a fullscreen(eightdivisions)display.

n.Switchto the l0 dB/DtVmodeand set the step attenuatorsfor 40 dB of attenuation.AdjustLog Lineai_ ity, R1060(Figure5-10)so the disptayis mid_screen.

olf a large change in the settingof R1060was f-q-Tregin part t, repeatthe adjustmenlsof R1012and R1030 becauseof interaction.

p.Checkthe accuracyof 10 ctB/DtVand 2 dB/DtV gfqPy-T9des by addingattenuationin 10 dB steps for

10 dB/DlVmodeand 1 dB stepsfor the 2 dBlDtV'rnode

an!that the disptaysteps

-gbsqrving1 major division, *0.25 minordivision,for eictrl0 A'estep,jnd 0.5 divi_

sion, r0.5 minordivision,for the 2 dB mode. (Readjust the signalgeneratoroutputto establisha newreference level after each step.) After the accuracyof the indivi_ dual steps has been verified,reset the signallevelfor full screen.

q.Add appropriatestep attenuationto step the displaydown screenand measurethe worst caseerror over the dynamic range. Error must not exceed

11.5dB overthe first 80 dB of range,or11.0 dB over

the 16 dB range.

r.lf the 10 dB log step in the 2 dB/DtVmodeis long,adjustgainwithR1097for lessgainandrebalance R1012.

s.Set the step attenuatorsto 10 dB and activate 2 dBlDtv.

t.set the Ref Levetto -15dBm and adjustthe sig- nal generatoroutput for a full screen display in the 2 dB/DlVmode.

u.PressLIN and adjustLin MocJeBalance,R102S (Figure5-13)for a fullscreendisptay.Amplitudeof LtN, zdBlDlV, and 10dB/DtVdisptayshouldnow be the sarne.

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