Tektronix TDS 420A User manual

Service Manual
TDS 420A, TDS 430A & TDS 460A
Digitizing Oscilloscopes
S/N B080000 and above
070-9703-06
Revsion A
Warning
The servicing instructions are for use by qualified
personnel only. To avoid personal injury, do not
perform any servicing unless you are qualified to
do so. Refer to all safety summaries prior to
performing service.
www.tektronix.com

Copyright ©Tektronix, Inc. All rights reserved.
Tektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes
that in all previously published material. Specifications and price change privileges reserved.
Tektronix, Inc., P.O. Box 500, Beaverton, OR 97077
TEKTRONIX and TEK are registered trademarks of Tektronix, Inc.

WARRANTY
Tektronix warrants that the products that it manufactures and sells will be free from defects in materials and workmanship
for a period of three (3) years from the date of shipment. If a product proves defective during this warranty period,
Tektronix, at its option, either will repair the defective product without charge for parts and labor, or will provide a
replacement in exchange for the defective product.
In order to obtain service under this warranty, Customer must notify Tektronix of the defect before the expiration of the
warranty period and make suitable arrangements for the performance of service. Customer shall be responsible for
packaging and shipping the defective product to the service center designated by Tektronix, with shipping charges prepaid.
Tektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the
Tektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any
other charges for products returned to any other locations.
This warranty shall not apply to any defect, failure or damage caused by improper use or improper or inadequate
maintenance and care. Tektronix shall not be obligated to furnish service under this warranty a) to repair damage resulting
from attempts by personnel other than Tektronix representatives to install, repair or service the product; b) to repair
damage resulting from improper use or connection to incompatible equipment; c) to repair any damage or malfunction
caused by the use of non-Tektronix supplies; or d) to service a product that has been modified or integrated with other
products when the effect of such modification or integration increases the time or difficulty of servicing the product.
THIS WARRANTY IS GIVEN BY TEKTRONIX IN LIEU OF ANY OTHER WARRANTIES, EXPRESS OR
IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TEKTRONIX’ RESPONSIBILITY TO
REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO
THE CUSTOMER FOR BREACH OF THIS WARRANTY. TEKTRONIX AND ITS VENDORS WILL NOT BE
LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES IRRESPECTIVE
OF WHETHER TEKTRONIX OR THE VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH
DAMAGES.

Contacting Tektronix
Phone [phone]*
Address Tektronix, Inc.
Department or name (if known)
14200 SW Karl Braun Drive
P.O. Box 500
Beaverton, OR 97077
USA
Web site www.tektronix.com
Sales support 1-800-833-9200, select option 1*
Service support 1-800-833-9200, select option 2*
Technical support Email: [e-mail]
1-800-833-9200, select option 3*
1-503-627-2400
6:00 a.m. -- 5:00 p.m. Pacific time
*This phone number is toll free in North America. After office hours, please leave a
voice mail message.
Outside North America, contact a Tektronix sales office or distributor; see the
Tektronix web site for a list of offices.

TDS 420A, TDS 430A & TDS 460A Service Manual i
Table of Contents
List of Figures iii............................................
List of Tables vi.............................................
General Safety Summary ix...................................
Service Safety Summary xi....................................
Preface xiii...................................................
Introduction xvi..............................................
Before Servicing xvi.................................................
Strategy for Servicing xvi.............................................
Tektronix Service xvii................................................
Specifications
Product Description 1--1........................................
Nominal Traits 1--7............................................
Warranted Characteristics 1--15..................................
Typical Characteristics 1--23.....................................
Operating Information
Installation 2--1...............................................
Supplying Operating Power 2--1........................................
Operating Environment 2--3...........................................
Applying and Interrupting Power 2--4....................................
Repackaging Instructions 2--5..........................................
Installed Options 2--5.................................................
Operating Information 2--7.....................................
Screen Layout 2--7...................................................
Basic Procedures 2--7.................................................
Theory of Operation
Theory of Operation 3--1.......................................
Logic Conventions 3--1...............................................
Module Overview 3--1................................................
Performance Verification
Performance Verification Procedures 4--1.........................
Brief Procedures 4--5...........................................
Self Tests 4--5.......................................................
Functional Tests 4--7.................................................
Performance Tests 4--15.........................................
Prerequisites 4--15....................................................
Equipment Required 4--16..............................................
Test Record 4--18.....................................................

Table of Contents
ii TDS 420A, TDS 430A & TDS 460A Service Manual
Signal Acquisition System Checks 4--20...................................
Time Base System Checks 4--34.........................................
Trigger System Checks 4--38............................................
Output Signal Check 4--53..............................................
Sine Wave Generator Leveling Procedure 4--55.............................
Adjustment Procedures
Adjustment Procedures 5--1.....................................
Requirements for Performance 5--1......................................
Usage 5--2.........................................................
Equipment Required 5--5..............................................
Adjustment Instructions 5--7...........................................
Probe Adjustment 5--10................................................
Monitor Assembly Adjustment 5--21.....................................
Maintenance
Maintenance 6--1..............................................
Related Maintenance Procedures 6--1....................................
Preparation 6--2.....................................................
Inspection and Cleaning 6--4...........................................
Removal and Installation Procedures 6--9.........................
Preparation — Please Read 6--9........................................
Access Procedure 6--13................................................
Procedures for Module Removal and Installation 6--23.......................
Disassembly for Cleaning 6--71..........................................
Troubleshooting 6--75...........................................
Diagnostics 6--75.....................................................
Firmware Updates 6--76................................................
Troubleshooting Equipment 6--77........................................
Options
Electrical Parts List
Diagrams
Mechanical Parts List

Table of Contents
TDS 420A, TDS 430A & TDS 460A Service Manual iii
List of Figures
Figure 1--1: TDS 400A Dimensional Drawing 1--13...................
Figure 2--1: Map of Display Functions 2--8........................
Figure 4--1: Map of Display Functions 4--3........................
Figure 4--2: Verifying Adjustments and Signal Path Compensation 4--6
Figure 4--3: Universal Test Hookup for Functional Tests 4--8.........
Figure 4--4: Initial Test Hookup 4--20..............................
Figure 4--5: Initial Test Hookup 4--23..............................
Figure 4--6: Initial Test Hookup 4--26..............................
Figure 4--7: Measurement of Analog Bandwidth 4--29................
Figure 4--8: Initial Test Hookup 4--31..............................
Figure 4--9: Measurement of Channel Delay 4--33....................
Figure 4--10: Initial Test Hookup 4--34.............................
Figure 4--11: Measurement of Accuracy — Long-Term and
Delay-Time 4--37............................................
Figure 4--12: Initial Test Hookup 4--38.............................
Figure 4--13: Initial Test Hookup 4--41.............................
Figure 4--14: Measurement of Trigger Sensitivity 4--43...............
Figure 4--15: Initial Test Hookup 4--45.............................
Figure 4--16: Confirming Auxiliary Triggering at Maximum
Triggering Frequency 4--46...................................
Figure 4--18: Initial Test Hookup 4--49.............................
Figure 4--19: Adjusting Sync Pulse Amplitude 4--51..................
Figure 4--20: Measurement of Video Sensitivity 4--52.................
Figure 4--21: Initial Test Hookup 4--54.............................
Figure 4--22: Measurement of Probe Compensator Limits 4--55........
Figure 4--23: Sine Wave Generator Leveling Equipment Setup 4--56....
Figure 4--24: Equipment Setup for maximum Amplitude 4--57.........
Figure 5--1: Hookup for Probe Compensation 5--10..................
Figure 5--2: Performing Probe Compensation 5--11..................
Figure 5--3: Proper and Improper Probe Compensation 5--12..........
Figure 5--4: Exposing the Inner Probe Tip 5--13.....................
Figure 5--5: Initial Test Hookup 5--13..............................
Figure 5--6: Exposing the Probe Body 5--16.........................

Table of Contents
iv TDS 420A, TDS 430A & TDS 460A Service Manual
Figure 5--7: Initial Test Hookup 5--16..............................
Figure 5--8: Probe Test Hookup 5--18..............................
Figure 5--9: Locations of Probe Adjustments 5--19...................
Figure 5--10: Adjustments vs. Front-Corner Response 5--20...........
Figure 5--11: Monitor Adjustment Locations 5--23...................
Figure 5--12: Five and Ten Percent Luminance Patches 5--24..........
Figure 5--13: Composite Pattern for Focusing 5--25..................
Figure 6--1: Oscilloscope Orientation 6--11..........................
Figure 6--2: Cabinet and Front-Panel Mounted Modules 6--16.........
Figure 6--3: Internal Modules 6--19................................
Figure 6--4: Cables and cable routing, B010100 -- B079999 6--22.......
Figure 6--5: Cables and cable routing, B080000 & up 6--23............
Figure 6--6: Knob and shaft removal 6--25..........................
Figure 6--7: Line fuse and line cord removal 6--26...................
Figure 6--8: Front cover, rear cover, cabinet, emi gasket,
and cabinet handle and feet removal 6--28.......................
Figure 6--9: Trim ring, menu elastomer, and menu
buttons removal 6--31........................................
Figure 6--10: EMI gasket removal and installation 6--33..............
Figure 6--11: Disk drive removal 6--34.............................
Figure 6--12: A06 Front-Panel assembly, ESD shield,
and menu flex and probe code flex circuits removal 6--36..........
Figure 6--13: Disassembly of the front-panel assembly 6--37...........
Figure 6--14: A05 Attenuator removal 6--40.........................
Figure 6--15: A26 Monitor assembly removal 6--43...................
Figure 6--16: A08 Jumper board assembly, D1 Bus,
and board supports removal 6--44.............................
Figure 6--17: A03 CPU removal 6--46..............................
Figure 6--18: A02 Display assembly removal 6--48....................
Figure 6--19: A09 DSP assembly removal 6--49......................
Figure 6--20: A01 Backplane assembly and its mount removal 6--51.....
Figure 6--21: Battery removal 6--54................................
Figure 6--22: Power factor correction module
removal, B080000 & up 6--56.................................
Figure 6--23: A24 Low voltage power supply
removal, B080000 & up 6--59.................................
Figure 6--24: A25 Low voltage power supply
removal, B010100 -- B079999 6--61.............................
Figure 6--25: Fan and fan mount removal 6--64......................

Table of Contents
TDS 420A, TDS 430A & TDS 460A Service Manual v
Figure 6--26: Line filter removal 6--65..............................
Figure 6--27: Auxiliary power supply
removal, B010100 -- B079999 6--68.............................
Figure 6--28: A04 Acquisition Board Removal 6--70..................
Figure 6--29: Accessing the protection switch 6--76...................
Figure 6--30: Console port connections 6--79........................
Figure 6--31: Primary Troubleshooting Procedure 6--80...............
Figure 6--32: A03 CPU Board Connector P1 6--81....................
Figure 6--33: Module Isolation Troubleshooting Procedure 6--82.......
Figure 6--34: Low Voltage Power Supply
Troubleshooting Procedure 6--84..............................
Figure 6--35: Power Supply Overload
Troubleshooting Procedure 6--86..............................
Figure 6--36: A25 Low Voltage Power
Supply Module (Right Side) 6--87..............................
Figure 6--37: Monitor Troubleshooting Procedure 6--88...............
Figure 6--38: Horizontal and Vertical Sync Signals 6--89..............
Figure 6--39: A Video Signal with White, Black,
and Blanking Levels 6--89....................................
Figure 6--40: A26 Monitor Connector J440 6--90.....................
Figure 6--41: A07 Auxiliary Power Connectors J4 and J7 6--90.........
Figure 6--42: A02 Display Connector J2 6--91.......................
Figure 6--43: Processor/Front Panel Troubleshooting Procedure 6--92...
Figure 6--44: A06 Front Panel Board Power Connectors
J101 and J106 6--93.........................................
Figure 6--45: Attenuator/Acquisition Troubleshooting Procedure 6--94..
Figure 6--46: A08 Jumper and A05 Attenuator Boards
Signal Locations 6--95.......................................
Figure 6--47: Acquisition and Attenuator Power
Troubleshooting Procedure 6--96..............................
Figure 6--48: A04 Acquisition Board Power Connector 6--97...........
Figure 6--49: Backplane Troubleshooting Procedure 6--98.............
Figure 6--50: A01 Backplane Module 6--100..........................
Figure 6--51: I2C Isolation Troubleshooting Procedure 6--101...........
Figure 6--52: Console Troubleshooting Procedure 6--102...............
Figure 9--1: TDS 400A Interconnections, B010100 -- B079999 9--2.....
Figure 9--2: TDS 400A Interconnections, B010100 -- B079999 (Cont) 9--3
Figure 9--3: TDS 400A Block Diagram, B010100 -- B079999 9--4.......
Figure 9--4: TDS 400A Block Diagram, B010100 -- B079999 (Cont) 9--5

Table of Contents
vi TDS 420A, TDS 430A & TDS 460A Service Manual
Figure 9--5: TDS 400A Interconnections, B080000 & up 9--6..........
Figure 9--5: TDS 400A Interconnections, B080000 & up (Cont.) 9--7...
Figure 9--6: TDS 400A Block Diagram, B080000 & up 9--8...........
Figure 9--6: TDS 400A Block Diagram, B080000 & up (Cont.) 9--9....
Figure 10--1: External and front panel modules 10--7.................
Figure 10--2: Internal modules (B010100 - B079999) 10--9.............
Figure 10--3: Internal modules (B080000 - Up) 10--11..................
Figure 10--4: Cables and routing (B010100 - B079999) 10--13...........
Figure 10--5: Cables and routing (B080000 - Up) 10--15................

Table of Contents
TDS 420A, TDS 430A & TDS 460A Service Manual vii
List of Tables
Table 1--1: Key Features of the TDS 400A Oscilloscopes 1--1.........
Table 1--2: Record Length vs. Divisions per Record 1--3.............
Table 1--3: Nominal Traits —Signal Acquisition System 1--7.........
Table 1--4: Nominal Traits —Time Base System 1--9...............
Table 1--5: Nominal Traits —Triggering System 1--9...............
Table 1--6: Nominal Traits —Display System 1--10..................
Table 1--7: Nominal Traits —Data Storage 1--10....................
Table 1--8: Nominal Traits —GPIB Interface, Video Output, and
Power Fuse 1--10...........................................
Table 1--9: Nominal Traits —Mechanical 1--11.....................
Table 1--10: Warranted Characteristics —Signal Acquisition
System 1--15...............................................
Table 1--11: Warranted Characteristics —Time Base System 1--17.....
Table 1--12: Warranted Characteristics —Triggering System 1--18....
Table 1--13: Warranted Characteristics —Probe Compensator
Output 1--18...............................................
Table 1--14: Warranted Characteristics —Power Requirements 1--18..
Table 1--15: Warranted Characteristics —Environmental, Safety,
and Reliability 1--19........................................
Table 1--16: Certifications and compliances 1--20....................
Table 1--17: Typical Characteristics —Signal Acquisition System 1--23.
Table 1--18: Typical Characteristics —Time Base System 1--24........
Table 1--19: Typical Characteristics —Triggering System 1--25.......
Table 1--20: Typical Characteristics —Data Handling 1--26..........
Table 2--1: Power-Cord Conductor Identification 2--2...............
Table 2--2: Power Cord Identification 2--2.........................
Table 2--3: Effects of Corrupted Data 2--4.........................
Table 4--1: Test Equipment 4--16.................................
Table 4--2: DC Offset Accuracy 4--22..............................
Table 4--3: Analog Bandwidth (TDS 420A) 4--27....................
Table 4--4: Analog Bandwidth (TDS 430A and TDS 460A) 4--28.......
Table 5--1: Adjustments Required for Module Replaced 5--3.........
Table 5--2: Adjustments and Dependencies 5--4....................
Table 5--3: Test Equipment, Fixtures, and Supplies 5--5.............

Table of Contents
viii TDS 420A, TDS 430A & TDS 460A Service Manual
Table 5--4: GPIB Board Configuration1 5--7.......................
Table 6--1: Relative Susceptibility to Static-Discharge Damage 6--3....
Table 6--2: External Inspection Check List 6--5....................
Table 6--3: Internal Inspection Check List 6--6.....................
Table 6--4: Tools Required for Module Removal 6--12................
Table 6--5: Access Instructions for Modules in Figure 6--2 6--15........
Table 6--6: Access Instructions for Modules in Figure 6--3 6--17........
Table 6--7: Access (and Removal) Instructions for Cables
in Figure 6--4 6--20.........................................
Table 6--8: Troubleshooting Test Equipment, Fixtures,
and Supplies 6--77..........................................
Table 6--9: Connections for a 9 to 25 Pin Null Modem Cable 6--78.....
Table 6--10: Diagnostic Failure Priority Lists 6--83..................
Table 6--11: Normal Output Voltage 6--85..........................
Table 6--12: Power Supply Maximum Current 6--87.................
Table 6--13: Front Panel Connector Voltages 6--93...................
Table 6--14: Channel and P1 Signal Locations 6--95.................
Table 6--15: A05 Attenuator Board Power 6--96.....................
Table 6--16: A04 Acquisition Board Power 6--97.....................
Table 6--17: Regulator Voltages 6--99..............................
Table 6--18: J7 Voltages 6--99....................................
Table 6--19: J8 Front Panel Voltages 6--99..........................
Table 7--1: International Power Cords 7--2........................
Table 7--2: Standard Accessories 7--2.............................
Table 7--3: Optional Accessories 7--3.............................
Table 7--4: Compatible Probes 7--3...............................
Table 7--5: Accessory Software 7--5...............................

TDS 420A, TDS 430A & TDS 460A Service Manual ix
General Safety Summary
Review the following safety precautions to avoid injury and prevent damage to
this product or any products connected to it.
To avoid potential hazards, use this product only as specified.
Only qualified personnel should perform service procedures.
Use Proper Power Cord. To avoid fire hazard, use only the power cord specified
for this product.
Avoid Electric Overload. To avoid electric shock or fire hazard, do not apply a
voltage to a terminal that is outside the range specified for that terminal.
Avoid Electric Shock. To avoid injury or loss of life, do not connect or disconnect
probes or test leads while they are connected to a voltage source.
Ground the Product. This product is grounded through the grounding conductor
of the power cord. To avoid electric shock, the grounding conductor must be
connected to earth ground. Before making connections to the input or output
terminals of the product, ensure that the product is properly grounded.
Do Not Operate Without Covers. To avoid electric shock or fire hazard, do not
operate this product with covers or panels removed.
Use Proper Fuse. To avoid fire hazard, use only the fuse type and rating specified
for this product.
Do Not Operate in Wet/Damp Conditions. To avoid electric shock, do not operate
this product in wet or damp conditions.
Do Not Operate in an Explosive Atmosphere. To avoid injury or fire hazard, do not
operate this product in an explosive atmosphere.
Use Proper Power Source. Do not operate this product from a power source that
applies more than the voltage specified.
Provide Proper Ventilation. To prevent product overheating, provide proper
ventilation.
Do Not Operate With Suspected Failures. If you suspect there is damage to this
product, have it inspected by qualified service personnel.
Injury Precautions
Product Damage
Precautions

General Safety Summary
xTDS 420A, TDS 430A & TDS 460A Service Manual
Terms in this Manual. These terms may appear in this manual:
WARNING. Warning statements identify conditions or practices that could result
in injury or loss of life.
CAUTION. Caution statements identify conditions or practices that could result in
damage to this product or other property.
Terms on the Product. These terms may appear on the product:
DANGER indicates an injury hazard immediately accessible as you read the
marking.
WARNING indicates an injury hazard not immediately accessible as you read the
marking.
CAUTION indicates a hazard to property including the product.
Symbols on the Product. The following symbols may appear on the product:
Protective Ground
(Earth) Terminal
ATTENTION
Refer to Manual
DANGER
High Voltage
Refer to the specifications section for a listing of certifications and compliances
that apply to this product.
Symbols and Terms
Certifications and
Compliances

TDS 420A, TDS 430A & TDS 460A Service Manual xi
Service Safety Summary
Only qualified personnel should perform service procedures. Read this Service
Safety Summary and the General Safety Summary before performing any service
procedures.
Do Not Service Alone. Do not perform internal service or adjustments of this
product unless another person capable of rendering first aid and resuscitation is
present.
Disconnect Power. To avoid electric shock, disconnect the main power by means
of the power cord or, if provided, the power switch.
Use Caution When Servicing the CRT. To avoid electric shock or injury, use
extreme caution when handling the CRT. Only qualified personnel familiar with
CRT servicing procedures and precautions should remove or install the CRT.
CRTs retain hazardous voltages for long periods of time after power is turned off.
Before attempting any servicing, discharge the CRT by shorting the anode to
chassis ground. When discharging the CRT, connect the discharge path to ground
and then the anode. Rough handling may cause the CRT to implode. Do not nick
or scratch the glass or subject it to undue pressure when removing or installing it.
When handling the CRT, wear safety goggles and heavy gloves for protection.
Use Care When Servicing With Power On. Dangerous voltages or currents may
exist in this product. Disconnect power, remove battery (if applicable), and
disconnect test leads before removing protective panels, soldering, or replacing
components.
To avoid electric shock, do not touch exposed connections.
X-Radiation. To avoid x-radiation exposure, do not modify or otherwise alter the
high-voltage circuitry or the CRT enclosure. X-ray emissions generated within
this product have been sufficiently shielded.

Service Safety Summary
xii TDS 420A, TDS 430A & TDS 460A Service Manual

TDS 420A, TDS 430A & TDS 460A Service Manual xiii
Preface
This service manual provides service information for the TDS 420A, TDS 430A,
and TDS 460A Digitizing Oscilloscopes.
STOP. If servicing a TDS 430A, follow the procedures for the TDS 460A, but
ignore all references to CH 3 and CH 4.
Manual Structure
This manual is divided into Chapters such as Specifications and Theory of
Operation. Further, it is divided into subsections such as Product Description
and Removal and Installation Procedures.
Sections containing procedures also contain introductions to those procedures.
Be sure to read these introductions because they provide information needed to
do the service correctly and efficiently. A brief description of each manual
chapter follows:
HSpecifications contains a product description of the digitizing oscilloscope
and tables of the characteristics and descriptions that apply to it.
HOperating Information is this chapter. It includes a description of how this
manual is structured as well as general information and operating instruc-
tions at the level needed to safely power on and service this oscilloscope. A
statement of the service strategy that this manual supports and instructions
for shipment of the digitizing oscilloscope are found in this chapter.
HTheory of Operation contains circuit descriptions that support general service
and fault isolation.
HPerformance Verification contains a collection of procedures for confirming
that this digitizing oscilloscope functions properly and meets warranted
limits.
HAdjustment Procedures contains a collection of procedures for adjusting this
digitizing oscilloscope to meet warranted limits.
HMaintenance contains information and procedures for doing preventive and
corrective maintenance of the digitizing oscilloscope. Instructions for
cleaning, for module removal and installation, and for fault isolation to a
module are found here.

Preface
xiv TDS 420A, TDS 430A & TDS 460A Service Manual
HOptions contains information on the factory-installed options that may be
present in your oscilloscope.
HElectrical Parts List contains a statement referring you to the Mechanical
Parts List, where both electrical and mechanical modules are listed.
See below.
HDiagrams contains a block diagram and an interconnection diagram useful
for isolating failed modules.
HMechanical Parts List includes a table of all replaceable modules, their
descriptions, and their Tektronix part numbers.
Manual Conventions
This manual uses certain conventions which you should become familiar with
before doing service.
Throughout this manual, any replaceable component, assembly, or part of this
digitizing oscilloscope is referred to generically as a module. In general, a
module is an assembly, like a circuit board, rather than a component, like a
resistor or an integrated circuit. Sometimes a single component is a module; for
example, the chassis of the oscilloscope is a module.
Symbols and terms related to safety appear in the General Safety Summary and
Service Safety Summary found at the beginning of this manual.
Besides the symbols related to safety, this manual uses the following symbols:
STOP. This “stop sign” labels information which you must read in order to
correctly do service and to avoid incorrectly using or applying
service procedures.
The clock icon labels procedure steps which require a pause to wait
for the oscilloscope to complete some operation before you
can continue.
Various icons such as the example icon at the left are used in
procedures to help identify certain readouts and menu functions
on screen.
Modules
Safety
Symbols

Preface
TDS 420A, TDS 430A & TDS 460A Service Manual xv
Related Manuals
These other manuals are available for the TDS 430A, TDS 420A, and TDS 460A
Digitizing Oscilloscopes:
HThe Reference gives you a quick overview of how to operate your oscillo-
scope.
HThe User Manual provides instructions on how to operate your oscilloscope.
HThe Programmer Manual provides complete information on programming
and remote control of the oscilloscope through the GPIB.

xvi TDS 420A, TDS 430A & TDS 460A Service Manual
Introduction
This section contains general information critical to safe and effective servicing
of this oscilloscope, the manual service strategy, and a description of repair and
warranty services available from Tektronix.
Before Servicing
This manual is for servicing the TDS 420A, TDS 430A, & TDS 460A Digitizing
Oscilloscopes. To prevent injury to yourself or damage to the oscilloscope, do
the following before you attempt service:
HBe sure you are a qualified service person.
HRead the safety summaries found at the beginning of this manual.
HRead Strategy for Servicing and Supplying Operating Power in
this subsection.
When using this manual for servicing, be sure to heed all warnings, cautions,
and notes.
STOP. If servicing a TDS 430A, follow the procedures for the TDS 420A, but
ignore all references to CH 3 and CH 4.
Strategy for Servicing
STOP. Throughout this manual, any field-replaceable component, assembly, or
part of this oscilloscope is referred to generically as a module.
This manual contains all the information needed for periodic maintenance of
your oscilloscope. (Examples of such information are procedures for checking
performance and for readjustment.) Further, it contains all information for
corrective maintenance down to the module level. This means that the proce-
dures, diagrams, and other troubleshooting aids help isolate failures to a specific
module, rather than to components of that module. Once a failure is isolated,
replace the module with a fully tested module obtained from the factory.
All modules are listed in Chapter 10, Mechanical Parts List. To isolate a failure
to a module, use the fault isolation procedures found in Chapter 6, Maintenance.