Tektronix 494AP service manual O a o o o

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494A/494APServiceVot. 1

TABLEOF CONTENTS(Conr.)

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				page
Section6 MAINTENANCE
(Conr)
FirmwareVersionand
Enor Message
Readout				6-15
SelectedComponents
	..................
ReplacingEPROM				6-15
or ROMDevices		........		6-15
Surface-Mounted
Components
Replacing			.....6_16
Surface-Mount€d
Components		..............		6_17
Transistor
and Integrated
CircuitConfigurations				,..
DiodeCotorCode				6_17
				6	g
MultipleTerminal					1
(Harmonica)					g
Connectors
ResistorValues	...............			6_1
		.........		6-1g
CapacitorMarking			.....6_1g
Soldering	...................				g
Techniques
Replacing	pin			6-1
the Square		for
the Multi-pin
Connectors				6_1g
Servicing
the VR Module				6-1g
REPLACING
ASSEMELIES
ANDSUBASSEMBLTES
	....................
Removing				6	19
and Installing
theGPIBBoard		.........			6-22
Removing
or Replacing
Semi-rigid
CoaxialCables				6_22
Replacing
the DualDiode
Assembty		............		6_22
in the 1st Mixer
Replaeing		......		6_23
the Crt
Repairing
the Crt
TraceRotationCoil				... 6-29
FrontPanelAssembly
Front-Panel	Removal...6-29
BoardRemoval				6_24
ReplacingFrontpanel
Pushbutton
Switches				6	24
MainPowerSuppty
ModuleRemoval		........		6_24
HighVottagepowerSupply				6_25
Removingand Replacingthe
lst LO				.. 6 _ 25
Replacing
the l st LO
InterfaceBoard		.........		6_25
FanAssembtyRernovaf				6-25
MAINTENANCE
ADJUSTMENTS				6.26
110MHztF Assembty
ReturnLossCalibration				6-26
.............2072MHz2ndConverter				6_26
FourCavityFilter		...........		6_27
Mixer		...........			,9 - 27
110MHzThreeCavityFitter				6_29
829MHz Converter
Maintenance	..............			6_29
Troubleshooting
and Calibrating
the2ndLO				..6-32

	Page
Preparingthe 2nd LO
Assemblyfor Adjustment	6	-35
Reassemblingthe
2ndLO Assembty	.....6	-9g

Troubleshooting
and Calibrating
the 16-20 MHz PhaseLock
Section	6-40
Troubleshooting
Aidsfor the
2182MHzPhaseLocked
2ndLO Assembty	.....6-42
100MHzOsciltatorin the
3rdConverter	649
l st ConverterBias	6-,44.
AuxiliarySynthesizer
VCOAdjustment	6-44
BaselineLeveling
(VideoProcessor)	.....6-46
10 MHzReference
OscillatorAccuracy	.. 6-49

MICROCOMPUTERSYSTEM

MATNTENANCE............. ....6-50

OptionSwitches.......6-50

Power-upSelfTest... 6-50

MicrocomputerSystemTest ........6-51

AddressBusTest.....6-52

MicrocomputerBus .................6-52

MernoryAddressDecoders.....6-52

ProcessorAddressDecoder....6-59

GPIBBoard

AddressDecoders6-s3

ClocksahdControlLines.........6-54

InstrumentBusTest6-54

TROUBLESHOOTINGONTHE

INSTRUMENTBUS6-54

InstrumentBus DataTransfers....6-54

InstrumentBusRegisters,............6-56

Front-PanelRegisters6-62

TAPEOATATRANSFERPROGRAM.... 6-63

Section 7 THEORYOF OPERATION
FUNCTTONALDESCRpTtON		.... 7- 1
Whatlt Does	-	...........7 - 1
How lt Works	.......	7 - 1
First,Second,and	...........	7- 1
ThirdGonverters
lF Section	.. -		7 - 2
DisplaySection		.... 7 - 2
FrequencyControl Section .,....7			-2
Counterand
PhaseLock Section		, ...7 - 2
DigitalControl Section		7	-3
PowerSupplySection		7	- 3
OtherSections		7	- 3