Tektronix 494AP service manual O o t, A a o o o a o o, O o a o o o, O o o o o o

494A1494APServlceVol. 1

TABLEOF CONTENTS(Cont.)

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			Page
Section7 THEORYOF OPERATTON(Cont)
DETAILEDDESCRPTON			7-4
1STCONVERTER		.............	7_4
	SECTTON
RFInterface			7-4
'l	Qircuits
st Converter			,,,7..-4
	...............RF Input		7-4
	Preselector		,.....74
	Circuits
	lst Mixer	..............	7	5
	1stLocalOscillator		7	5
	powerDivider	......	7-s
	TransferSwitch		.... 7-s
	DirectionalFilter		,......Z-6
	2O72MHztF Fitters....
	DiplexerandFilter...,...............Z-6
2NDCONVERTER		............	7_7
	SECTTON
2072MHz 2ND CONVERTER.......7-8
	Four-Cavity		-g
	Fiter		Z
	MixerCircuit		7-g
	PrecisionExternal	........	7-9
	Cables
	Filterto Mixer
	RF InputGable		7-10
	2nd LO to Mixer
	LO InputCable		Z-10
2182MHzPHASELocKED
2NDLO				7-10
	2182MHzMicrostrip
	Oscillator	.............	7-10
	2200MHz Reference
	Board			7-11
	220OMHz Reference
	Mixer	........... 7 - 11
	16-20MHz phaselock
	Board			7-11
829MHz2NDCONVERTER				7-19
	lF Section	............	7,13
	829MHzDiplexer.,..............7-tg
	829MHzAmplifier		t-13
	829MHz 2ndConverter...,..7-14
	110MHzlF Seect		7 - i5
	LO Section	...........	7-16
	PhaseLock	..............	7-16
	Circuit
	2nd LocalOscillator
	OuputCircuit		... 7-19
	719MHz OutputCircuit.......7-18
3RDCONVERTER
	SECTION......,.....7-19
110MHztF AMpLtFtER			7 - 19
110MHzFILTERS
		..............	7-2A
3rdCONVERTER
	100MHzOscillator		7	20
	Mixer	...........	7_20
	DistributionAmplifier		7-20
	Calibrator	.............		2-21
REFERENCE		,...............7-21
	LOCK
	ExternalReferance
	Det€ctor	...,...,,..,...7-21

			Page
FrequencySynchronizer				7-21
Phase/Frequency
Detector	...,.,..,.....,7-21
TuneAmplifier				7-22
LockDetector		"..		7-22
rF sEcTtoN				7-22
VARABLERESOLUTION				7-22
VRfnput	...............			7-22
1stFilterSelect		.....7-22
100Hz and10Hz	..............			7-24
BandpassFilter
1stMixer	,..,,.....7-25
BandpassFilter		,.,..7-25
2ndMixer	.........			7-25
LocalOscillator				7-26
10 dB GainSteps	-			7-26
20dB GainSteps				7-26
BandLevelingCircuit		,......7-27
VR MotherBoards				7-27
2ndFilterSelect		....7-28
PostVRAmplifierCircuit				7-28
LOGAMPand DETEGTOR				7-29
LogAmplifierCircuits				7-29
DetectorCircuit		.-...7-31
DTSPLAYSECTTON	........			7€3
FUNCTIONALDESCRIPTION			7-33
VIDEOAMPLIFIER		.,,.7.33
LogModeCircuits			7-33
LinearModeCircuits			7--.34
PulseStretchCircuit				7-34
ldentifyCircuit	.......			7-35
DigitalControlCircuit			7-35
vrDEopRocESSoR			7-35
Interfacewith 1405TV
SidebandAdapter		-		7-35
MdeoMarker				7-36
VideoLeveling	,.................7-37
VideoLevelerCircuits				7€7
VideoFilterCircuits	,..........7-37
VideoBlanking.-		,........7-39
DIGITALSTORAGE				7-39
VerticafSection		.....740
DigitizingCircuits				743
Address Decoding				7-43
InterfaceLogic	, ........743
MaximumHold				743
ConstantCircuit				7 - 43
OutputCircuits				7 - 44
Peak/Average Level				7 - 44
Circuits
HorizontalSection	-			7 - 44
MarkerlC				7 - 46
Tracking Digital-to-
Analog Converter	................			7*46
Update Marker Circuits				746

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