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Service
Manual
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Tektronix
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I
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494A
& 494AP
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Spectrum
Analyzers
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Volume
1
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a
070-ss60-00
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Warning
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The
servicing instructions
are for use by qualified
personnel
only. To avoid personal
injury, do
not
o
perform
any servicing unless
you are qualified
to
do so. Refer
o to the Safety Summary
prior to
performing
service.
o
Please check
for change information
at the rear
o
of this manual.
o
First Edition:
January 1 987
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o
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I o o o ? o Copyright @ Tekrronix, Inc. 1987. All rights reserved. a Tektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes o that in all previously published material. Specifications and price change privileges reserved. o Printed in the U.S.A. t Tektronix, Inc., P.O. Box 1000, Wilsonville, OR 97070_1000 o TEKTRONIX and TEK are registered trademarks of Tektronix. o Inc. O o o o o a o o o o o o o o o o o o o a o o o
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o o o o o RELEASE OF COPYRIGHT o Tektronix provide cannot manuals for measurement products that are no o longer eligible for long term support. Tektronix hereby grants permission and license for others to reproduce and distribute copies of any Tektronix o measurement product manual, including user manuals, operato/s part manuals, service o manuals, and the (a) like, that have a Tektronix Number (b) and are for a measurement product that is no longer o supported by Tektronix. A Tek
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o a o o ,.'.t a o a o a a o o o t a a o I o o o o o o o O a I o a o a o o t a o o a a a a a
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I o o I o I WARRANTY t I Tektronix warrants that this product will be free from defects in materials and workmanship fbr a period of one (l) year from the date of shipment. o If any such product proves defective during this warranty Tektronix, at its feriod, option, either will repair the defective product without charge for parts and labor, or will provide a replacement o in exchange for the defective product. I In order to obtain service under this warranty, Customer
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O a o I ? o a a a a a I t o I a a a O o O o o o t C a I a o O t a o a o a o o a o o I o
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o o 494A/494AP Service Vot. 1 o t o PREFACE o I This manual contains servic€ information I for . - the ANSI Y1.1 Abbreviations TEKTRONfX 494A1494Ap. The information is tocated in . - o two volumes. Volume ANSI Y32.2 Graphic 1 Symbots contains the text and Volume 2 contains the diagrams and parts lists. The Tabte o - of IEEE 91 Logic Symbots a Contents in each volume lists the contents of both volumes. O Change/History Inf ormation Manuals that describe other aspects
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o o o I a o t a a a o a o o I O a a a o o o o o o o t o a a o o I o o o a o o o a o a o
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o o 494A/494AP Service Vot. 1 o t o TABLE OF CONTENTS o The 494A/494AP service Manuat is divided into two volumes. o VOLUME 1 o o Page Page PREFACE o ........................ i Section 4 PERFORMANCE CHECK TABLE OF CONTENTS .............. .......... iii o Introduction LIST OF ILLUSTRATTONS ..,.4-1 ........... ........ x LIST Incoming OF TABLES Inspection Test ...................... 4_1 ............. xiii a SERVICING Option Instrument SAFETY Checks ..............,...... SUMMA
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o 49441494AP Servtce Vot. i o o I .| TABLE OF (Gonr.) CONTENTS r page Page o Section 4 PERFORMANCE CHECK (Conr.) 15. Adjust Band Leveling for Waveguide Bands o .............. 24. Check LO 5-25 Emission .....4-29 16. PhasE Lock Calibration .................... point 25. Check 1 5-2S dB Compression .......4-29 a OPTION INSTRUMENTS ONLY ............. 26. 5-29 Check External Reference 17. Adjust Option 07 VR Band Leveling Input Power 5-29 .... 4-31 a 18. Adjust Option 42 Module ......
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o o 494A/494AP Service Vot. 1 o I O TABLE OF CONTENTS (Conr.) I page Page I Section 6 MAINTENANCE (Conr) Preparing the 2nd LO o Assembly Firmware for Adjustment Version and ............. 6-35 o Enor Reassembling Message the Readout ............... 6-1 5 2nd LO Assembty Selected Components ..... 6-9g .................. 6-1 5 O Replacing Troubleshooting EPROM and Calibrating or ROM the 16-20 MHz Phase I Devices Lock ........ 6-15 Section Surface-Mounted ..................... C
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a 494A1494AP Servlce Vol. 1 o o o 't TABLE OF CONTENTS (Cont.) o Page Page o Section 7 THEORY OF OPERATTON (Cont) Frequency Synchronizer .......... 7-21 a Phase/Frequency DETAILED -4 DESCR|PT|ON ................ ..... 7 Detector ...,.,..,.....,7-21 1ST CONVERTER SECTTON ............. 7_4 a Tune Amplifi er ............... ........... 7-22 RF Interface .................... Qircuits 7-4 'l -22 Lock Detector .............. ......... 7 st Converter ................. ".. ..........,,,..
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o o 494A1494AP Service Vot. I o o o TABLE OF CONTENTS (Conr.) o Page Page O Section 7 THEORY OF OPERATION (Conr) lst LO DRIVER .........7-67 a Digital Controf Fast ...... 7-6g Retrace Blanking ...,.,... 742 Input Switching ........................ Memories 7-69 o ........7-47 Oscillator Filter DEFLECTION AMPLIFIERS .......... 7-47 o Switch Driver Horizontal .......7-69 Section ...............,... 747 Summing Amptifier ................... 7-69 Vertical Section ....249 o Oscillat
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o 4944/494AP Servlce Vot. 1 a o I TABLE , OF CONTENTS (Cont.) a Page Page o Section 7 THEORY OF OPERATTON (Conr) POWER SUPPLY ..........7-103 o Primary Circuits ........ 7-103 DtctTAL CONTROL SECTTON .......... 7_88 Line Input Circuits .................... 7-1 03 Microcomputer ............................. 7-gg a Invert€r Circuit ..... 7-103 Processor ............. 7-gg Multivibrator .... 7-103 o Microprocessor ................... 7-88 Ramp Generator .................. 7-l 04 Cfock .
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494A/{94AP Service Vot. 1 TABLE OF CONTENTS (Cont.) VOLUME 2 Sec|ion 9 REPLACEABLE ELECTRICAL PARTS Section 10 DTAGRAMS Section 1.I REPLACEABLE MECHANICAL PARTS
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I 494A/494AP Servlce Vol. 1 a o o t LIST OF ILLUSTRATIONS t a page Figure Figure Page a The 494AP o Spectrum Analyzer. ................... xvi Test of 4-23 oscilloscope display VERT output with a full screen display o 2-1 Dimensions. ....,....,..2-12 on the Spectrum Analyzer. .......4-34 Equipment 4-24 setup for checking o 3-1 Location of input power selector switch Option 07 frequency response and fine I fuse. .._....... .....,..,.........9-2 from 0.01 GHz to 1 GHz. .......... 4-35 4
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I o 494A/494AP Servtce Vot. 1 o a o LIST OF ILLUSTRATIONS (Conr.) I I Figure Page o Flgure Page 5-21 PreseleetorDriver o construction details. .................. 6-gg adjustment setup. ......... ............5_22 6-23 2182MHz 2nd LO Phase Lock a 5-22 Preselector Driver test point adjustment setup. ........ .............. 6_39 and adjustment locations ........... S_Zg I 6-24 Tune and Sweep Range 5-23 Test equipment setup for band adjustments ............641 leveling adjus
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o 494A/494AP Servlce Vot. 1 I o a LIST I OF ILLUSTRATIONS (Cont.) I o Figure Page Figure Page a 7-12 Selection of position disptay o 7-23 Simplified digital-to-analog on the log scale. .....7-94 converter. ....-........ 7-66 I 7-13 Functional diagram showing the 7-24 Simplified span decade attanuator. .............. 7-67 sp€ctrum analyzer and 1405 TV 7-25 DAC variance graph. ................7-73 I Sideband Adapter system. ........ 7€6 7-26 Simpfffied tune voltage converter. ........
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o a 494A1494AP Service Vot. 1 o a o LIST OF TABLES O I Table page Table page I 1-1 TEKTRON'X WAVEGUIDE MIXERS .............. 1-3 6-6 EQUIPMENT REQUIRED FOR RETURN O LOSS ADJUSTMENT ...............6-27 2-1 FREQUENCY RELATED o 6-7 EOUIPMENT REQUIRED FOR CHARACTERTSTTCS .................. 2-1 2nd LO CALIBRATION ................................. 6-94 2-2 o AMPLITUDE RELATED 6-8 EQUIPMENT REQUIRED FOR CHARACTERTSTTCS ................. 2_6 CALIBRATING THE 16-20 MHz I 2-3 INPUT
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o {944/494AP Service Vot. 1 o o a I LIST OF TABLES (Cont.) o ) Table page page Table I 8.1 EXTENDED SERVICE AND 84 OPTION 41 ALTERNATE o WARRANW OPT|ONS .............8_1 SPECTF|CAT|ONS ......... ............8-4 8.2 OPNON 07 ALTERNATE 8-5 o OPTION 42 ELECTRICAL spEctFtcATloNs ................... 8-2 CHARACTERTSTTCS .................. 8-5 8.3 OPTIONS o 21 AND 22 WAVEGUIDE MtxERS CHARACTERTSTTCS ...................... 8_3 I o t o I o t a I o I o O I O I o t a t I a o I o I a I a a o
