Tektronix TDS 644A, TDS 640A, TDS 620A Service Manual

Service Manual

Tektronix

TDS 620A, 640A & 644A
Digitizing Oscilloscope

070-8718-04

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.

Copyright © Tektronix, Inc. 1993. 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.

Printed in the U.S.A.

Tektronix, Inc., P.O. Box 1000, Wilsonville, OR 97070-1000

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.

Specifications

Table of Contents

List of Figures vii

List of Tables xi

Safety Summary xiii

Specifications 1-1

General Product Description 1-1
User Interface 1-2

Menus 1-2
Indicators 1-2
General Purpose Knob 1-2
GUI 1-2

Signal Acquisition System 1-3
Horizontal System 1-3
Trigger System 1-4
Acquisition Control 1-4
On-Board User Assistance 1-5

Help 1-5

Autoset 1-5

Measurement Assistance 1-5

Cursor 1-5

Measure 1-5
Digital Signal Processing (DSP) 1-6

Storage and I/O 1-6
Display 1-7

Zoom 1-7

Nominal Traits 1-9

Warranted Characteristics 1-13

Typical Characteristics 1-19

TDS 620A, 640A, & 644A Service Manual v

Table of Contents

Operating Information

Using this Manual 2-1

Before Servicing 2-1
Strategy for Servicing 2-1
Manual Structure 2-2
Manual Conventions 2-3

Modules 2-3
Safety 2-3
Symbols 2-3

Tektronix Service 2-4

Warranty Repair Service 2-4
Repair or Calibration Service 2-4
Self Service 2-5

Finding Other Information 2-5

General Information 2-7

Supplying Operating Power 2-7

Power Cord Information 2-8
Operating Voltage 2-9
Memory Backup Power 2-9

Operating Environment 2-9

Operating Temperature 2-9
Ventilation Requirements 2-9

Applying and Interrupting Power 2-10

Power On 2-10
Power Off 2-10

Repackaging Instructions 2-11
Installed Options 2-11

General Operating Instructions 2-13

Screen Layout 2-13
Basic Procedures 2-13

How to Power On 2-13
How to Use Help 2-14
How to Use the Status Menu 2-14
How to Set Functions 2-15
How to Set Complex Functions 2-18

Theory of Operation

Circuit Description 3-1

Logic Conventions 3-1
Module Overview 3-1

ii Contents

Performance Verification

Brief Procedures 4-1

Performance Tests 4-13

Table of Contents

General Instructions 4-1
Conventions 4-2
Self Tests 4-4

Verify Internal Adjustment, Self Compensation,

and Diagnostics 4-4

Functional Tests 4-6

Verify All Input Channels 4-7
Verify the Time Base 4-8
Verify the Main and Delayed Trigger Systems 4-9
Verify the File System (Optional on TDS 620A and 640A) ... 4-11

Prerequisites 4-13
Equipment Required 4-14

Test Record 4-17

Signal Acquisition System Checks 4-21

Check Accuracy of Offset (Zero Setting) 4-21
Check DC Gain and Voltage Measurement Accuracy 4-23
Check Analog Bandwidth 4-29
Check Delay Between Channels 4-33

Time Base System Checks 4-37

Check Accuracy for Long-Term Sample Rate, Delay Time,

and Delta Time Measurements 4-37

Trigger System Checks 4-40

Check Accuracy (Time) for Pulse-Glitch or Pulse-Width

Triggering 4-40
Check Accuracy, Trigger-Level or Threshold, DC Coupled .. 4-43
Sensitivity, Edge Trigger, DC Coupled 4-46

Output Signal Checks 4-51

Check Outputs—AUX1 (for TDS 620A) or CH 3 (for

TDS 640A or 644A), Main and Delayed Trigger 4-51
Check Probe Compensator Output 4-54

Option 05 Video Trigger Checks 4-59

Check Video Trigger 4-59

Adjustment Procedures

Adjustment Procedures 5-1

TDS 620A, 640A, & 644A Service Manual

Requirements for Performance 5-1

Personnel 5-1
Warm-Up Period 5-1
Access 5-2
System 5-2

iii

Table of Contents

Optional Peripherals 5-2
Test Equipment 5-2

Usage 5-2

Performing the Adjustments 5-3
Complete Adjustment 5-3
Individual Adjustments 5-3
Partial Adjustment 5-4
Adjustment After Repair 5-4
Adjustment Dependencies 5-4

Equipment Required 5-5
Adjustment Instructions 5-6

Hardware Installation 5-6
Software Installation 5-7
Software-Based Adjustments 5-7

Probe Adjustment for the P6139A Probe 5-10

Compensate the Probe 5-10
Measure Probe Bandwidth 5-12
Adjust the Probe — High Frequency Response 5-14

Display Assembly Adjustment 5-18

Brightness and Contrast Adjustment

(TDS 620A and 640A - Monochrome - Only) 5-18

Rotation, Brightness, and Contrast Adjustment

(TDS 644A - Color - Only) 5-21

Maintenance

Maintenance Information 6-1

Procedures Not In This Section 6-1
Preventing ESD 6-2

Precautions 6-2
Susceptibility to ESD 6-2

Inspection and Cleaning 6-5

General Care 6-5
Inspection and Cleaning Procedures 6-5

Inspection — Exterior 6-6
Cleaning Procedure — Exterior 6-6
Inspection — Interior 6-7
Cleaning Procedure — Interior 6-8
Lubrication 6-8

Removal and Installation Procedures 6-9

Preparation — Please Read 6-9

List of Modules 6-10
General Instructions 6-10
Summary of Procedures 6-10

iv Contents

Table of Contents

Access Procedure 6-16
Procedures for External Modules 6-17

Front-Panel Knobs 6-17

Line Fuse and Line Cord 6-18

EMI Gaskets 6-19

Rear Cover and Cabinet 6-20

Front Cover, Trim Ring, Menu Buttons, and Attenuator Panel 6-23
A12 Front-Panel Assembly 6-25

Display-Frame Assembly 6-28
Cabinet Modules 6-29

Procedures for Outer-Chassis Modules 6-31

A15 Attenuator Assembly 6-31

Fan 6-32
A14 D1 Bus and Analog-Power and Digital-Power Cables .. 6-33
A23 SerPar Board — RS232/Centronics Hardcopy Interface 6-35
A29 Video Trigger Board 6-37
A11 Processor/Display Board 6-42
Top Cover and Board Brackets 6-44

Rear-Panel Cables 6-45
A10 Acquisition Board 6-46

Floppy Disk 6-48

Rear Chassis 6-50

Procedures for Inner-Chassis Modules 6-52

A16 Low Voltage Power Supply 6-52
A20 or A30 Display Assembly and Supply Fuse 6-53

Front Subpanel 6-58

Main Chassis 6-59

Disassembly for Cleaning 6-60

Troubleshooting 6-63

Diagnostics 6-63
Firmware Updates 6-64

TDS 620A, 640A, & 644A Service Manual ix

Table of Contents

Options

Electrical Parts List

Diagrams

Mechanical Parts List

vi Contents

List of Figures

Figure 2-1: Power-Cord Plug Identification 2-8
Figure 2-2: Map of Display Functions 2-14
Figure 4-1: Map of Display Functions 4-3
Figure 4-2: Verifying Adjustments and Signal-Path Compensation .. 4-5
Figure 4-3: Universal Test Hookup for Functional Tests 4-7
Figure 4-4: Measurement of DC Offset Accuracy at Zero Setting ... 4-23
Figure 4-5: Initial Test Hookup 4-24
Figure 4-6: Measurement of the DC Accuracy for Delta

Measurements 4-25

Figure 4-7: Measurement of DC Accuracy at Maximum Offset

and Position 4-28
Figure 4-8: Initial Test Hookup 4-29
Figure 4-9: Measurement of Analog Bandwidth 4-32
Figure 4-10: Initial Test Hookup 4-34
Figure 4-11: Measurement of Channel Delay 4-35
Figure 4-12: Initial Test Hookup 4-37
Figure 4-13: Measurement of Accuracy — Long-Term and

Delay Time 4-38
Figure 4-14: Initial Test Hookup 4-40
Figure 4-15: Measurement of Time Accuracy for Pulse and

Glitch Triggering 4-42
Figure 4-16: Initial Test Hookup 4-43
Figure 4-17: Measurement of Trigger-Level Accuracy 4-45
Figure 4-18: Initial Test Hookup 4-47
Figure 4-19: Measurement of Trigger Sensitivity 4-48
Figure 4-20: Initial Test Hookup 4-51
Figure 4-21: Measurement of Main Trigger Out Limits 4-52
Figure 4-22: Initial Test Hookup 4-54
Figure 4-23: Measurement of Probe Compensator Frequency 4-56
Figure 4-24: Subsequent Test Hookup 4-57
Figure 4-25: Measurement of Probe Compensator Amplitude 4-58
Figure 4-26: Jitter Test Hookup 4-60
Figure 4-27: Jitter Test Displayed Waveform 4-60
Figure 4-28: Jitter Test When Completed 4-62
Figure 4-29: Triggered Signal Range Test — 300 mV 4-63
Figure 4-30: Triggered Signal Range Test — 75 mV 4-64
Figure 4-31: 60 Hz Rejection Test Hookup 4-65
Figure 4-32: 60 Hz Rejection Test Setup Signal 4-65
Figure 4-33: Subsequent 60 Hz Rejection Test Hookup 4-66

TDS 620A, 640A, & 644A Service Manual vii

List of Figures

Figure 4-34: 60 Hz Rejection Test Result 4-67
Figure 4-35: Line Count Accuracy Test Hookup 4-68
Figure 4-36: Line Count Accuracy Test Setup Waveform 4-68
Figure 4-37: Line Count Accuracy Correct Result Waveform 4-69
Figure 4-38: PG502 Setup for Sync Duty Cycle Test 4-71
Figure 4-39: Sync Duty Cycle Test: One-Div Neg Pulse Waveform .. 4-72
Figure 4-40: Sync Duty Cycle Test: Critically Adjusted Pulse 4-73
Figure 5-1: Accessing the Protection Switch 5-8
Figure 5-2: Hookup for Probe Compensation 5-10
Figure 5-3: Performing Probe Compensation 5-11
Figure 5-4: Proper and Improper Probe Compensation 5-11
Figure 5-5: Exposing the Inner Probe Tip 5-12
Figure 5-6: Initial Test Hookup 5-12
Figure 5-7: Exposing the Probe Body 5-14
Figure 5-8: Initial Test Hookup 5-15
Figure 5-9: Locations of P6139A Probe Adjustments 5-17
Figure 5-10: Adjustments versus Front-Corner Response 5-17
Figure 5-11: TDS 620A/640A Five and Ten Percent Luminance

Patches 5-19

Figure 5-12: TDS 644A Five and Ten Percent Luminance Patches .. 5-22
Figure 6-1: External Modules 6-12
Figure 6-2: Outer-Chassis Modules 6-13
Figure 6-3: Inner-Chassis Modules - TDS 620A or 640A with

A20 Display Assembly 6-14

Figure 6-4: Inner-Chassis Modules - TDS 644A with A30

Display Assembly 6-15

Figure 6-5: Knob Removal 6-18
Figure 6-6: Line Fuse and Line Cord Removal 6-19
Figure 6-7: Rear Cover and Cabinet Removal 6-22
Figure 6-8: Front Cover, Trim Ring, Menu Buttons, and Attenuator

Panel Removal (Front Cover not Shown) 6-23

Figure 6-9: A12 Front-Panel Assembly Removal 6-26
Figure 6-10: Disassembly of Front-Panel Assembly 6-27
Figure 6-11: Cabinet Modules Removal 6-30
Figure 6-12: Attenuator Interconnect Cable Routing and

Jack Locations 6-32

Figure 6-13: A14 D1 Bus and Analog-Power and Digital-Power

Cables Removal 6-33

Figure 6-14: Remove Circuit Board Assembly From Oscilloscope .. 6-35
Figure 6-15: Remove Circuit Board From Assembly 6-36
Figure 6-16: Circuit Board Installed 6-38
Figure 6-17: Proper Routing of the Video Cable 6-39
Figure 6-18: Circuit Board Removal 6-40
Figure 6-19: A11 Processor/Display Removal 6-43

viii

Contents

List of Figures

Figure 6-20: Board Bracket Removal 6-44
Figure 6-21: A10 Acquisition Board Removal 6-47
Figure 6-22: Floppy Disk Removal 6-49
Figure 6-23: Rear Chassis Removal 6-51
Figure 6-24: A16 Low Voltage Power Supply Removal 6-53
Figure 6-25: Display Assembly Removal - TDS 644A 6-55
Figure 6-26: Display Assembly Removal - TDS 620A and 640A ... 6-56
Figure 6-27: Display Driver Board Removal 6-57
Figure 6-28: Front Subpanel Removal 6-59
Figure 6-29: Accessing the Protection Switch 6-64
Figure 6-30: Primary Troubleshooting Procedure 6-65
Figure 6-31: Module Isolation Troubleshooting Procedure 6-67
Figure 6-32: A16 Low Voltage Power Supply Module Isolation

Troubleshooting Procedure 6-68
Figure 6-33: Power Supply Voltage Measurement Locations 6-70
Figure 6-34: Color (TDS 644A) Display Troubleshooting Procedure . 6-71
Figure 6-35: Horizontal and Vertical Sync Signals - Color Display . 6-72
Figure 6-36: A Video Signal with White, Black, and Blanking

Levels - Color Display 6-72
Figure 6-37: Monochrome (TDS 620Aand 640A) Display

Troubleshooting Procedure 6-73
Figure 6-38: Horizontal and Vertical Sync Signals - Monochrome

Display 6-74
Figure 6-39: A Video Signal with White, Black, and Blanking

Levels - Monochrome Display 6-74

Figure 6-40: Processor/Acquisition Troubleshooting Procedure .... 6-75

Figure 6-41: Processor/Front Panel Troubleshooting Procedure .... 6-76

Figure 6-42: Attenuator/Acquisition Troubleshooting Procedure .... 6-77

Figure 6-43: A11 DRAM Processor/Display Module (View of

Right Side) 6-78

Figure 6-44: A11 DRAM Processor/Display Module (View of

Upper Left Corner) 6-79
Figure 6-45: A11 DRAM Processor/Display Module (View of

Lower Left Corner) 6-79
Figure 6-46: A10 Acquisition Module (View of Lower Left Corner) .. 6-80
Figure 9-1: Block Diagram 9-2
Figure 9-2: Interconnections 9-4
Figure 10-1: External Modules 10-5
Figure 10-2: Outer-Chassis Modules 10-7
Figure 10-3: Inner-Chassis Modules - A30 Display Shown 10-9
Figure 10-4: Cables 10-11
Figure 10-5:Floppy Disk 10-13
Figure 10-6: Accessories 10-14

TDS 620A, 640A, & 644A Service Manual ix

List of Figures

Contents

List of Tables

Table 1-1: Record Length versus Divisions per Record, Samples

per Division, and Sec/Div Sequence 1-3

Table 1-2: Nominal Traits — Signal Acquisition System 1-9
Table1-3: Nominal Traits — Time Base System 1-10
Table1-4: Nominal Traits — Triggering System 1-10
Table1-5: Nominal Traits — Display System 1-11
Table 1-6: Nominal Traits — GPIB Interface, Output Ports, and

Power Fuse 1-11

Table 1-7: Nominal Traits — Mechanical 1-12
Table 1-8: Warranted Characteristics — Signal Acquisition System . 1-13
Table 1-9: Warranted Characteristics — Time Base System 1-14
Table 1-10: Warranted Characteristics — Triggering System 1-15
Table 1-11: Warranted Characteristics — Output Ports, Probe

Compensator, and Power Requirements 1-15

Table 1-12: Warranted Characteristics — Environmental 1-16
Table 1-13: Typical Characteristics — Signal Acquisition System ... 1-19
Table 1-14: Typical Characteristics — Time Base System 1-20
Table 1-15: Typical Characteristics — Triggering System 1-20
Table 1-16: Typical Characteristics — Data Handling and Reliability 1-22
Table 2-1: Power-Cord Conductor Identification 2-8
Table 2-2: Effects of Corrupted Data 2-10
Table 4-1: Test Equipment 4-14
Table 4-2: DC Offset Accuracy (Zero Setting) 4-22
Table 4-3: DC Accuracy 4-27
Table 4-4: Analog Bandwidth 4-30
Table 5-1: Calibration Tests 5-3
Table 5-2: Adjustments Required for Module Replaced 5-4
Table 5-3: Adjustments and Dependencies 5-4
Table 5-4: Test Equipment, Fixtures, and Supplies 5-5
Table 5-5: GPIB Board Configuration 5-7
Table 6-1: Relative Susceptibility to Static-Discharge Damage 6-3
Table 6-2: External Inspection Check List 6-6
Table 6-3: Internal Inspection Check List 6-7
Table 6-4: Tools Required for Module Removal 6-11
Table 6-5: Normal Supply Voltages (Measured on J26 and J27

on the A11 DRAM Processor/Display Module) 6-69

Table 6-6: No-Load Supply Voltages (Measured on J5 and J6

on the A17 Main LV Power Supply Module) 6-69

Table 7-1: International Power Cords 7-1

TDS 620A, 640A, & 644A Service Manual xi

List of Tables

Table 7-2: Standard Accessories 7-3
Table 7-3: Optional Accessories 7-4
Table 7-4: Accessory Software 7-5

xii Contents

Please take a moment to review these safety precautions. They are provided
for your protection and to prevent damage to the Digitizing Oscilloscopes.
This safety information applies to all operators and service personnel.

Symbols and Terms These two terms appear in manuals:

caut

• L

• ij««»™^ statements identify conditions or practices that could result in

These two terms appear on equipment:

• CAUTION indicates a personal injury hazard not immediately accessible

!?!L1 statements identify conditions or practices that could result in

damage to the equipment or other property.

personal injury or loss of life.

as one reads the marking, or a hazard to property including the equip-
ment itself.

Safety Summary

• DANGER indicates a personal injury hazard immediately accessible as
one reads the marking.

This symbol appears in manuals:

®

Static-Sensitive Devices

These symbols appear on equipment:

A

DANGER

High Voltage

Protective

ground (earth)

terminal

ATTENTION

Refer to
manual

TDS 620A, 640A, & 644A Service Manual

xiii

Safety Summary

Specific Precautions Observe all of the following precautions to ensure your personal safety and

to prevent damage to either the TDS 620A, 640A, & 644A or equipment
connected to it.

Do Not Perform Service While Alone

Do not perform internal service or adjustment of this product unless another
person capable of rendering first aid and resuscitation is present.

Use Care When Servicing With Power On

Dangerous voltages exist at several points in this product. To avoid personal
injury, do not touch exposed connections or components while power is on.
Disconnect power before removing protective panels, soldering, or replacing

components.

Power Source

The TDS 620A, 640A, & 644A is intended to operate from a power source
that will not apply more than 250 VRMs between the supply conductors or

between either supply conductor and ground. A protective ground connec-
tion, through the grounding conductor in the power cord, is essential for safe
system operation.

Grounding the Digitizing Oscilloscopes

The TDS 620A, 640A, & 644A are each grounded through the power cord. To
avoid electric shock, plug the power cord into a properly wired receptacle
where earth ground has been verified by a qualified service person. Do this

before making connections to the input or output terminals of the TDS 620A,
640A, & 644A.

Without the protective ground connection, all parts of the TDS 620A, 640A, &
644A are potential shock hazards. This includes knobs and controls that may
appear to be insulators.

Use the Proper Power Cord

Use only the power cord and connector specified for your product. Use only
a power cord that is in good condition.

Use the Proper Fuse

To avoid fire hazard, use only the fuse specified in the parts list for your

product, and which is identical in type, voltage rating, and current rating.

xiv

Safety

Safety Summary

Do Not Remove Covers or Panels

To avoid personal injury, do not operate the TDS 620A, 640A, & 644A without
the panels or covers.

Do Not Operate in Explosive Atmospheres

The TDS 620A, 640A, & 644A provides no explosion protection from static
discharges or arcing components. Do not operate the TDS 620A, 640A, &
644A in an atmosphere of explosive gasses.

Electric Overload

Never apply a voltage to a connector on the TDS 620A, 640A, & 644A that is
outside the range specified for that connector.

TDS 620A, 640A, & 644A Service Manual

XV

Safety Summary

xvi Safety

Specifications

This subsection begins with a general description of the traits of the
TDS 620A, 640A, & 644A Digitizing Oscilloscopes. Three subsections follow,
one for each of three classes of traits: nominal traits, warranted characteris-
tics, and typical characteristics.

General Product The TDS 620A, 640A, & 644A are portable, four-channel digitizing oscillo-
Description scopes suitable for use in a variety of test and measurement applications

p

and systems. Key features include:

• A maximum digitizing rate of 2 GS/s on each of the full-featured chan-
nels (four on the TDS 640A and 644A, two on the TDS 620A) simulta-
neously with an analog bandwidth of 500 MHz.

• Four input channels, each with 8-bit vertical resolution, and each with a
record length of 2,000 samples and 8-bit vertical resolution.

• Extensive triggering capabilities: such as edge, logic, and glitch. Video

trigger (Option 05) is also available. The video trigger modes are NTSC,
SECAM, PAL, HDTV, and FlexFormat™ (user definable format).

• Acquisition modes such as sample, envelope, and average.

• A full complement of advanced functions, like continuously-updated
measurements, results and local pass/fail decision making.

• Specialized display modes, such as variable persistence with color

grading, dot or vector mode, sin(x)/x or linear display filters, and user
selectable color pallettes. The "Fit to Screen" features compresses the
entire waveform record to fit on the screen.

• A unique graphical user interface (GUI), an on-board help mode, and a
logical front-panel layout which combine to deliver a new standard in
usability.

• Full GPIB software programmability. Hardcopy output using GPIB,
RS-232, or Centronics ports. RS-232 and Centronics are standard on

the TDS 644A and optional, as option 13, on the TDS 620A and 640A.

• VGA output for driving remote monitors.

• A 1.44 Mbyte, DOS 3.3 or later-compatible, floppy disk drive (option 1F

on the TDS 620A and 640A) and NVRAM mass storage for saving
waveforms, hardcopies, and oscilloscope setups.

• On the TDS 644A, a color display for distinguishing among waveforms,

their measurements, and associated text.

TDS 620A, 640A, & 644A Service Manual

1-1

Specifications

User Interface Use a combination of front-panel buttons, knobs, and on-screen menus to

control the oscilloscope's many functions. The front-panel controls are
grouped according to function: vertical, horizontal, trigger, and special. Set a
function you adjust often, such as vertical positioning or the time base
setting, directly by its own front-panel knob. Set functions which you change

less often, such as vertical coupling and horizontal mode, indirectly using

selected menus.

Menus

Pressing one (sometimes two) front-panel button(s), such as vertical menu,
displays a main menu of related functions, such as coupling, bandwidth,
etc., at the bottom of the screen. Pressing a main-menu button, such as
coupling, displays a side menu of settings for that function, such as AC, DC,
or GND (ground) coupling, at the right side of the screen. Pressing a side-

menu button selects a setting such as DC.

Indicators

On-screen readouts help you keep track of the settings for various functions,
such as vertical and horizontal scale and trigger level. Some readouts use
the cursors or the automatic parameter extraction feature (called measure)
to display the results of measurements made or the status of the instrument.

General Purpose Knob

Assign the general purpose knob to adjust a selected parameter function.

More quickly change parameters by toggling the SHIFT button. Use the
same method as for selecting a function, except the final side-menu selec-
tion assigns the general purpose knob to adjust some function, such as the

position of measurement cursors on screen, or the setting for a channel's
fine gain.

GUI

I ^ The user interface also makes use of a GUI, or Graphical User Interface, to

make setting functions and interpreting the display more intuitive. Some

J

< menus and status are displayed using iconic representations of function

settings such as those shown here for full, 100 MHz, and 20 MHz band-

J \ width. Such icons allow you to more readily determine status or the available

settings.

7-2

Specifications

Specifications

Signal Acquisition
Svstem

The signal acquisition system provides full-featured vertical channels (four
on the TDS 640A and 644A, two on the TDS 620A) with calibrated vertical
scale factors from 1 mV to 10 V per division. All four channels can be ac-
quired simultaneously.

Each of the four channels can be displayed, vertically positioned, and offset,
can have their bandwidth limited (100 MHz or 20 MHz) and their vertical
coupling specified. Fine gain can also be adjusted.

Besides these channels, up to three math waveforms and four reference
waveforms are available for display. (A math waveform results when you
specify dual waveform operations, such as add, on any two channels. A

reference waveform results when you save a live waveform in a reference

memory.)

Horizontal Svstem There are three horizontal display modes: main only, main intensified, and

delayed only. You can select among various horizontal record length set-
tings.

A feature called "Fit to Screen" allows you to view entire waveform records
within the 10 division screen area. In other words, waveforms are com-

pressd to fit on the screen. (see Table 1-1)

Table 1-1: Record Length versus Divisions per Record, Samples

per Division, and Sec/Div Sequence

Divisions per Record

Record Length

Record Length

Fit to Screen OFF Fit to Screen ON
50 (1-2.5-5) 50 (1-2.5-5)

500 10 divs 10 divs

1000 20 divs 10 divs

2000 40divs 10divs

Both the delayed only display and the intensified zone on the main intensi-
fied display may be delayed by time with respect to the main trigger. Both
can be set to display immediately after the delay (delayed runs after main

mode). The delayed display can also be set to display at the first valid
trigger after the delay (delayed-triggerable mode).

The delayed display (or the intensified zone) may also be delayed by a
selected number of events. In this case, the events source is the delayed-
trigger source. The delayed trigger can also be set to occur after a number
of events plus an amount of time.

Sample/Division (Sec/Div Sequence)

TDS 620A, 640A, & 644A Service Manual 1-3

Specifications

Trigger System The triggering system supports a varied set of features for triggering the

signal-acquisition system. Trigger signals recognized include:

• Edge (main- and delayed-trigger systems): This familiar type of trigger-

ing is fully configurable for source, slope, coupling, mode (auto or
normal), and holdoff.

• Logic (main-trigger system): This type of triggering can be based on

pattern (asynchronous) or state (synchronous). In either case, logic
triggering is configurable for sources, for boolean operators to apply to
those sources, for logic pattern or state on which to trigger, for mode

(auto or normal), and for holdoff. Time qualification may be selected in

pattern mode.

• Pulse (main-trigger system): Pulse triggering is configurable for trigger-

ing on runt or glitch pulses, or on pulse widths or periods inside or
outside limits that you specify. It is also configurable for source, polarity,

mode, and holdoff.

• Video (with option 05: Video Trigger): Video triggering is compatible with

standard NTSC, PAL, SECAM, and HDTV formats. An additional feature
called FlexFormat™ (flexible format) allows the user to define the video
format on which to trigger.

You can choose where the trigger point is located within the acquired wave-
form record by selecting the amount of pretrigger data displayed. Presets of
20%, 50%, and 80% of pretrigger data can be selected in the horizontal

menu, or the general purpose knob can be assigned to set pretrigger data

to any value within the 20% to 80% limits.

Acquisition Control You can specify a mode and manner to acquire and process signals that

matches your measurement requirements.

• Select the mode for interpolation of points sampled on non-repetitive
signals (linear or sin (x)/x. This can increase the apparent sample rate
on the waveform when maximum real-time rates are reached.

• Use sample, envelope, and average modes to acquire signals.

• Set the acquisition to stop after a single acquisition (or sequence of
acquisitions if acquiring in average or envelope modes), or after a limit
condition has been met.

• Select channel sources for compliance with limit tests. You can direct
the TDS to signal you or generate hard copy output either to a printer or
to a floppy disk (with option 1F) based on the results. Also, you can
create templates for use in limit tests.

7-4 Specifications

Specifications

On-Board User Help and autoset

can

assist you in setting up the Digitizing Oscilloscope to

Assistance make your measurements.

Help

Help displays operational information about any front-panel control. When
help mode is in effect, manipulating any front-panel control causes the
Digitizing Oscilloscope to display information about that control. When help
is first invoked, an introduction to help is displayed on screen.

Autoset

Autoset automatically sets up the Digitizing Oscilloscope for a viewable
display based on the input signal.

Measurement Once you have set up to make your measurements, the cursor and measure

Assistance features can help you quickly make those measurements.

Cursor

Three types of cursors are provided for making parametric measurements
on the displayed waveforms. Horizontal bar cursors (H Bar) measure vertical

parameters (typically volts). Vertical bar cursors (V Bar) measure horizontal
parameters (typically time or frequency) and now extend to the top and
bottom of the screen. Paired cursors measure both amplitude and time

simultaneously. These are delta measurements; that is, measurements

based on the difference between two cursors.

Both H Bar and V Bar cursors can also be used to make absolute measure-
ments; that is measurements relative to a defined level or event. For the

H Bars, either cursor can be selected to read out its voltage with respect to
any channels ground reference level. For the V Bars, it's time with respect to
the trigger point (event) of the acquisition and the cursors can control the

portion of the waveform on which automatic measurements are made.

For time measurements, units can be either seconds or Hertz (for 1/time).

When the video trigger option installed (Option 05), you can measure the
video line number using the vertical cursors. You can measure IRE ampli-
tude (NTSC) using the horizontal cursors with or without the video trigger
option installed.

Measure

Measure can automatically extract parameters from the signal input to the

Digitizing Oscilloscope. Any four out of the more than 25 parameters avail-
able can be displayed to the screen. The waveform parameters are mea-
sured continuously with the results updated on-screen as the Digitizing
Oscilloscope continues to acquire waveforms.

TDS 620A, 640A, & 644A Service Manual 1-5

Specifications

Digital Signal Processing (DSP)

An important component of the multiprocessor architecture of this Digitizing
Oscilloscope is Tektronix's proprietary digital signal processor, the DSF! This
dedicated processor supports advanced analysis of your waveforms when
doing such compute-intensive tasks as interpolation, waveform math, and
signal averaging. It also teams with a custom display system to deliver
specialized display modes (See Display, later in this description.)

and I/O Acquired waveforms may be saved in any of four nonvolatile REF (reference)

memories or on a 3.5 inch, DOS 3.3-or-later compatible disk. Any or all of
the saved waveforms may be displayed for comparison with the waveforms

being currently acquired.

The source and destination of waveforms to be saved may be chosen. You
can save any of the four channels to any REF memory or to move a stored

reference from one REF memory to another. Reference waveforms may also

be written into a REF memory location via the GFIB interface.

The Digitizing Oscilloscope is fully controllable and capable of sending and

receiving waveforms over the GFIB interface (IEEE Std 488.1-1987/IEEE
Std 488.2-1987 standard). This feature makes the instrument ideal for

making automated measurements in a production or research and develop-

ment environment that calls for repetitive data taking. Self-compensation
and self-diagnostic features built into the Digitizing Oscilloscope to aid in
fault detection and servicing are also accessible using commands sent from
a GFIB controller.

Another standard feature is hardcopy. This feature allows you to output
waveforms and other on-screen information to a variety of graphic printers
and plotters from the TDS front panel, providing hard copies without requir-

ing you to put the TDS into a system-controller environment. You can make

hardcopies in a variety of popular output formats, such as FCX, TIFF, BMF!

RLE, EFS, Interleaf, and EFS mono or color. You can also save hardcopies

in a disk file in any of the formats above. The hardcopies obtained are based
on what is displayed on-screen at the time hardcopy is invoked. The hardco-

pies can be stamped with date and time and spooled to a queue for printing
at a later time. You can output screen information via GFIB, RS-232C, or
Centronics interfaces.

7-6 Specifications

Specifications

Display

The TDS 620A, 640A, & 644A Digitizing Oscilloscopes offers flexible display
options. You can customize the following attributes of your display:

Color (on the TDS 644A): waveforms, readouts, graticule, and variable

persistence with color coding;

Intensity: waveforms, readouts, and graticule;

Style of waveform display(s): vectors or dots, intensified or non-intensi-
fied samples, infinite persistence, and variable persistence with color
coding;

Interpolation method: Sin(x)/x or Linear;

Display format: xy or yt with various graticule selections including NTSC

and PAL to be used with video trigger (option 05).

Zoom

This oscilloscope also provides an easy way to focus in on those waveform
features you wish to examine up close. By invoking zoom, you can magnify
the waveform parameter using the vertical and horizontal controls to expand

(or contract) and position it for viewing.

TDS 620A, 640A, & 644A Service Manual

1-7

Specifications

7-8 Specifications

Nominal Traits

This subsection contains a collection of tables that list the various nominal
traits that describe the TDS 620A, 640A, & 644A Digitizing Oscilloscope.

Electrical and mechanical traits are included.

Nominal traits are described using simple statements of fact such as "Four,
all identical" for the trait "Input Channels, Number of," rather than in terms of

limits that are performance requirements.

Table 1-2: Nominal Traits — Signal Acquisition System

Name

Bandwidth Selections

Samplers, Number of Four, simultaneous

Digitized Bits, Number of

Input Channels, Number of Four, all identical (TDS 640A/644A)

Input Coupling

Input Impedance Selections

Ranges, Offset

Range, Position ±5 divisions

Range, Sensitivity,
CH 1-CH 4 on the TDS 640A, 644A;
CH1, CH2, AUX1, and AUX2 on the
TDS 620A

Description

20 MHz, 100 MHz, and FULL (500 MHz)

1

8 bits

Two, all identical (TDS 620A)

DC, AC, or GND

1 MO or 50 O

Volts/Div Setting Offset Range

1 mV/div-99.5 mV/div ±1 V

100 mV/div-995 mV/div

1 V/div-10 V/div ±100 V

1 mV/div to 10 V/div

2

±10 V

1 Displayed vertically with 25 digitization levels (DLs) per division and 10.24 divisions dynamic range with zoom off. A DL is the

smallest voltage level change that can be resolved by the 8-bit A-D Converter, with the input scaled to the volts/division setting of
the channel used. Expressed as a voltage, a DL is equal to 1/25 of a division times the volts/division setting.

2 The sensitivity ranges from 1 mV/div to 10 V/div in a 1-2-5 sequence of coarse settings. Between a pair of adjacent coarse set-

tings, the sensitivity can be finely adjusted. The resolution of such a fine adjustment is 1% of the more sensitive of the pair. For
example, between 5o mV/div and 1o0 mV/div, the volts/division can be set with 0.5 mV resolution.

TDS 620A, 640A, & 644A Service Manual 1-9

Nominal Traits

Table 1-3: Nominal Traits — Time Base System

Name Description

Range, Sample-Rate1'

3

10 Samples/sec to 2 GSamples/sec on four (TDS 640A/644A) or two
(TDS 620A) channels simultaneously.

Range, Interpolated Waveform Rate2,

3

5 GSamples/sec to 100 GSamples/sec

(200 ps/Sample to 10 ps/Sample)

Range, Seconds/Division 500 ps/div to 5 s/div

Record Length Selection 500 samples, 1000 samples, 2000 samples.

1 The range of real-time rates, expressed in samples/second, at which a digitizer samples signals at its inputs and stores the sam-

ples in memory to produce a record of time-sequential samples.
2 The range of waveform rates for interpolated waveform records.

3 The Waveform Rate (WR) is the equivalent sample rate of a waveform record. For a waveform record acquired by real-time sam-

pling of a single acquisition, the waveform rate is the same as the real-time sample rate; for a waveform created by interpolation of

real-time samples from a single acquisition, the waveform rate is faster than the real time sample rate. For both cases, the wave-

form rate is 1/(Waveform Interval) for the waveform record, where the waveform interval (Wl) is the time between the samples in the

waveform record.

Table 1-4: Nominal Traits — Triggering System

Name Description

Range, Delayed Trigger Time Delay 16 ns to 250 s

Range, Events Delay 2 to 10,000,000

Range (Time) for Pulse-Glitch or Pulse-

2 ns to 1 s

Width Triggering

Ranges, Trigger Level or Threshold Source Range

Any Channel ±12 divisions from center of screen

Auxiliary ±8 V

Line ±300 V

Video Trigger Modes of Operation

(Option 05 Video Trigger)

Supports the following video standards:

• NTSC (525/60) - 2 field mono or 8 field

• PAL (625/50) - 2 field mono, 8 field, or SECAM

• HDTV -

(787.5/60)
(1050.60)
(1125/60)
(1250/60)

• FlexFormat™ (user definable standards)

User can specify: field rate, number of lines, sync pulse width
and polarity, line rate, and vertical interval timing.

1-10 Specifications

Table 1-5: Nominal Traits — Display System

Name Description

Nominal Traits

Video Display

Color (on the TDS 644A) or monochrome (on the TDS 620A, 640A)
display, 7 inch diagonal, with a display area of 5.04 inches horizon-
tally by 3.78 inches vertically

Video Display Resolution 640 pixels horizontally by 480 pixels vertically

Waveform Display Graticule

Single Graticule: 401 x 501 pixels, 8 x10 divisions, where divisions
are 1 cm by 1 cm

Waveform Display Colors Scale

TDS 644A: Sixteen colors in infinite-persistence or variable persis-
tence display with color coding.
TDS 620Aand 640A: Sixteen levels in infinite-persistence or varia-

ble-persistence display styles.

Table 1-6: Nominal Traits — GPIB Interface, Output Ports, and Power Fuse

Name Description

Interface, GPIB

Interface, RS-232

Interface, Centronics

GPIB interface complies with IEEE Std 488-1987

RS-232 interface complies with EIA/TIA 574 (talk only)

Centronics interface complies with Centronics interface standard
C332-44 Feb 1977, REV A

Interface, Video

VGA video output with levels that comply with ANSI R5343A stan-
dard. DB-15 connector.

Logic Polarity for Main- and Delayed- Negative TRUE. High to low transition indicates the trigger occurred.

Trigger Outputs

Fuse Rating Either of two fuses1 maybe used: a .25" x 1.25" (UL 198.6, 3AG):

6 A FAST, 250 V, or a 5 mm x 20 mm, (IEC 127): 5 A (T), 250 V.

1 Each fuse type requires its own fuse cap.

TDS 620A, 640A, & 644A Service Manual

1-11

Nominal Traits

Table 1-7: Nominal Traits — Mechanical

Name Description

Cooling Method Forced-air circulation with no air filter

Construction Material Chassis parts constructed of aluminum alloy; front panel con-

structed of plastic laminate; circuit boards constructed of glass lami-

nate. Cabinet is aluminum and is clad in Tektronix Blue vinyl materi-

al.

Finish Type Tektronix Blue vinyl-clad aluminum cabinet

Weight Standard TDS 644A Digitizing Oscilloscope

13.7 kg (30 lbs), with front cover.

25.1 kg (55 lbs), when packaged for domestic shipment.

Standard TDS 620A and 640A Digitizing Oscilloscope

12.3 kg (29 lbs), with front cover.

20.0 kg (44 lbs), when packaged for domestic shipment.

RackmountTDS 644A Digitizing Oscilloscope

13.7 kg (30 lbs) plus weight of rackmount parts, for the rack-
mounted Digitizing Oscilloscope (Option 1R).

Rackmount TDS 620A and 640A Digitizing Oscilloscope

12.3 kg (27 lbs) plus weight of rackmount parts, for the rack-
mounted Digitizing Oscilloscope (Option 1R).

Rackmount conversion kit

2.3 kg (5 lbs), for the rackmount conversion kit only; 3.6 kg
(8 lbs), when the kit is packaged for domestic shipping.

Overall Dimensions Standard Digitizing Oscilloscope

Height: 193 mm (7.6 in), with the feet installed.

Width: 445 mm (17.5 in), with the handle.

Depth: 434 mm (17.1 in), with the front cover installed.

Rackmount Digitizing Oscilloscope

Height: 178 mm (7.0 in).

Width: 483 mm (19.0 in).

Depth: 558.8 mm (22.0 in).

1-33

Specifications

Warranted Characteristics

This subsection lists the various warranted characteristics that describe the
TDS 620A, 640A, & 644A Digitizing Oscilloscopes. Electrical and
environmental characteristics are included.

Warranted characteristics are described in terms of quantifiable performance

limits which are warranted.

NOTE

In these tables, those warranted characteristics that are checked in
the procedure Performance Verification, found in Section 1, appear
in boldface type under the column Name.

As stated above, this subsection lists only warranted characteristics. A list of
typical characteristics starts on page 1-19.

Performance
Conditions

Table 1-8: Warranted Characteristics — Signal Acquisition System

Name Description

Accuracy, DC Gain

Accuracy, Offset

1

1

The electrical characteristics found in these tables of warranted characteris-
tics apply when the oscilloscope has been adjusted at an ambient tempera-
ture between +20° C and +30° C, has had a warm-up period of at least 20

minutes, and is operating at an ambient temperature between 0° C and
+50° C (unless otherwise noted).

±1.5%.

(For all sensitivities from 2 mV/div to 10 V/div and offsets from 0 to
±100 V)

At 1 mV/div ± 2.0%

Volts/Div Setting

1 mV/div - 99.5 mV/div ±(0.2% x Net Offset

100 mV/div - 995 mV/div ±(0.35% x Net Offset

1 V/div - 10 V/div

Offset Accuracy

+ 1.5 mV + 0.6 div)

+ 15mV + 0.6 div)

±(0.35% x Net Offset

+ 150 mV + 0.6 div)

2

2

2

TDS 620A, 640A, & 644A Service Manual 1-13

Warranted Characteristics

Table 1-8: Warranted Characteristics — Signal Acquisition System (Cont.)

Name

Analog Bandwidth, DC-50 O
Coupled, or DC-1 MO Coupled with

P6139A Probe

Description

Volts/Div Bandwidth

3

5 mV/div - 10 V/div DC - 500 MHz

2 mV/div - 4.98 mV/div DC - 300 MHz

1 mV/div - 1.99 mV/div DC - 200 MHz

Cross Talk (Channel Isolation) >100:1 at 100 MHz and >30:1 at the rated bandwidth for the chan-

nel's sensitivity rating, for any two channels having equal volts/divi-

sion settings

Input Impedance, DC-1 MO Coupled 1 MO ±0.5% in parallel with 10 pF ±2 pF

Input Impedance, DC-50 O Coupled

Input Voltage, Maximum, DC-1 MO,

50 O ±1% with VSWR < 1.3:1 from DC - 500 MHz

±400 V (DC + peak AC); derate at 20 dB/decade above 1 MHz

AC-1 MO, or GND Coupled

Input Voltage, Maximum, DC-50 O or

5 V

, with peaks less than or equal to ±30 V

RMS

AC-50 O Coupled

Lower Frequency Limit, AC Coupled

1 To ensure the most accurate measurements possible, run an SPC calibration first. When using the Digitizing Oscilloscope at a

Volts/Div setting of <5 mV/div, an SPC calibration should be run once per week to ensure that instrument performance levels meet

specifications.
2 Net Offset = Offset - (Position x Volts/Div). Net Offset is the voltage level at the center of the A-D converter's dynamic range. Offset

Accuracy is the accuracy of this Voltage level.

3 The limits given are for the ambient temperature range of 0°C to +30°C. Reduce the upper bandwidth frequencies by 2.5 MHz for

each °C above +30°C.
4 The AC Coupled Lower Frequency Limits are reduced by a factor of 10, when 10X passive probes are used.

<10 Hz when AC-1 MO Coupled; <200 kHz when AC-50 O

Coupled

4

Table 1-9: Warranted Characteristics — Time Base System

Name Description

Accuracy, Long Term Sample Rate ±100 ppm over any > 1 ms interval
and Delay Time

1-14

Specifications

Table 1-10: Warranted Characteristics — Triggering System

Warranted Characteristics

Name

Accuracy (Time) for Pulse-Glitch or

Pulse-Width Triggering

Sensitivity, Edge-Type Trigger, DC
Coupled

1

Description

Time Range

2 ns to 1 |is

1.02 |is to 1 s

Trigger Source

Accuracy

±(20% x | Setting | + 0.5 ns)

±(100 ns + 0.01% x | Setting | )

Sensitivity

Any Channel 0.35 division from DC to 50 MHz, increasing to

1 division at 500 MHz

0.25 volts from DC to 50 MHz

Minimum

Minimum Rearm Width

Pulse Width

2 ns

2 ns + 5% of Glitch Width

Width, Minimum Pulse and Rearm, for

Pulse Triggering

Auxiliary

Pulse Class

Glitch

Setting

Runt

Width

2.5 ns

2 ns

2.5 ns

2 ns + 5% of Width Upper Limit
Setting

Jitter (Option 05 Video Trigger) 17 nsp_p on HDTV signal; 60 nsp_p on NTSC or PAL signal

Input Signal Sync Amplitude for 0.6 division to 4 divisions with (1 to 4 divisions in numeric field)
Stable Triggering (Option 05 Video
Trigger)

1 The minimum sensitivity for obtaining a stable trigger. A stable trigger results in a uniform, regular display triggered on the se-

lected slope. The trigger point must not switch between opposite slopes on the waveform, and the display must not "roll" across
the screen on successive acquisitions. The TRIG'D LED stays constantly lighted when the SEC/DIV setting is 2 ms or faster but
may flash when the SEC/DIV setting is 10 ms or slower.

Table 1-11: Warranted Characteristics — Output Ports, Probe Compensator, and

Power Requirements

Name Description

Logic Levels, Main- and Delayed-
Trigger Outputs

Characteristic Limits

Vout (HI)

>2.5 V open circuit; > 1.0 V into a 50 O load to

ground

Vout (LO)

Vout (LO)

< 0.7 V into a load of <4 mA; < 0.25 V into a

50 O load to ground

Output Voltage and Frequency, Characteristic Limits

Probe Compensator

Output Voltage, Signal Out (CH 31)

Voltage 0.5 V (base-top) ±1% into a load of >50 O

Frequency

1 kHz ±5%

20 mV/division ±20% into a 1 MO load; 10 mV/division ±20% into a
50 O load

Source Voltage 90 to 250 VAC

, continuous range

RMS

Source Frequency 47 Hz to 63 Hz

TDS 620A, 640A, & 644A Service Manual 1-15

Warranted Characteristics

Table 1-11: Warranted Characteristics — Output Ports, Probe Compensator, and

Power Requirements (Cont.)

Name

Description

Power Consumption <300 W (450 VA)

1 CH 3 signal out is only present at the rear panel if CH 3 is selected as the trigger source for the main and/or delayed trigger sys-

tems.

Table 1-12: Warranted Characteristics — Environmental

Name Description

Atmospherics Temperature with floppy disk:

Operating: +4° Cto +50° C;

Non-operating: -22° Cto +60° C

Temperature without floppy disk:

Operating: 0° Cto +50° C;

Non-operating: -40° Cto +60° C

Relative humidity with floppy disk:

Operating: To 80%, at or below +29° C;

Operating: To 20%, at or below +50° C

Non-operating: To 90%, at or below +40° C;

Non-operating: To 5%, at or below +50° C

Relative humidity without floppy disk:

To 95%, at or below +40° C;

To 75%, from +41 ° C to +55° C

Altitude:

To 4570 m (15,000 ft.), operating;

To 12190 m (40,000 ft.), non-operating

Dynamics

Random vibration without floppy disk installed:

0.31 g rms, from 5 to 500 Hz, 10 minutes each axis, operating;

3.07 g rms, from 5 to 500 Hz, 10 minutes each axis, non-operat-
ing

Emissions Meets or exceeds the requirements of the following standards:

Vfg. 243/1991 Amended per Vfg. 46/1992

FCC Code of Federal Regulations, 47 CFR, Part 15, Subpart B,

Class A

User-Misuse Simulation Electrostatic Discharge Susceptibility: Up to 8 kV with no change to

control settings or impairment of normal operation; up to 15 kVwith

no damage that prevents recovery of normal operation

1-16 Specifications

Table 1-12: Warranted Characteristics — Environmental (Cont.)

Warranted Characteristics

Name

Description

Third Party Certification Conforms to and is certified where appropriate to:

UL1244

CSA-C22 No. 231

TDS 620A, 640A, & 644A Service Manual

1-17

Warranted Characteristics

1-18 Specifications

Typical Characteristics

This subsection contains tables that list the various typical characteristics
which describe TDS 620A, 640A, & 644A Digitizing Oscilloscope.

Typical characteristics are described in terms of typical or average

performance. Typical characteristics are not warranted.

Table 1-13: Typical Characteristics — Signal Acquisition System

Name Description

Accuracy, Delta Time Measurement For single-shot acquisitions using single-shoot sample acquisition

Frequency Limit, Upper, 100 MHz
Bandwidth Limited

Frequency Limit, Upper, 20 MHz
Bandwidth Limited

Calculated Rise Time

2

1

mode.

Time Measurement Error < .15 x Si + (100 ppm x |Reading|) + (Time

Per Div ^ 1000)

Add 50 ps (typical) Channel Skew for 2 channel measurements.

Sample calculation:
To measure the width of a 65.5 ns pulse at 2 GS/sec sampling,

Time Measurement Error

< (0.15 x 0.5 ns) + (1 x 10-4)(65.5 ns) + (25 ns/div. ^ 1000)
< 0.075 ns + 0.007 ns + 0.025 ns
< 107 ps

100 MHz

20 MHz

Volts/Div Setting

5 mV/div - 10 V/div 800 ps

2 mV/div - 4.98 mV/div

1 mV/div - 1.99 mV/div

Rise Time

1.3 ns

2.0 ns

Delay Between Channels, Full
Bandwidth

Step Response Settling Errors

1 The limits are given for signals having pulse height > 5 div, reference level = 50% mid-point, filter set to Sin (x) /x acquired at

>5 mV/div, 1.4 <

TDS 620A, 640A, & 644A Service Manual 1-19

Tr

,Si < 5, where Si is the hardware sample interval and tr is the signal rise time.

<50 ps for any two channels with equal volts/division and coupling

settings

Volts/Div Setting

1 mV/div - 99.5 mV/div <2 V <0.5 <0.2 <0.1

100 mV/div - 995 mV/div

1 V/div - 10 V/div <200 V <1.0 <0.5 <0.2

± Step Settling Error (%)3 at

Response

20 ns 100 ns 20 ms

<20 V <1.0 <0.5 <0.2

Typical Characteristics

The numbers given are valid 0°C to +30°C and will increase as the temperature increases due to the degradation in bandwidth.
Rise time is calculated from the bandwidth. It is defined by the following formula:

Rise Time (ns) =

Note that if you measure rise time, you must take into account the rise time of the test equipment (signal source, etc.) that you use
to provide the test signal. That is, the measured risetime (RTm) is determined by the instrument risetime (RTi) and the risetime of
the test signal source (RTgen) according to the following formula:

RTm 2 = RTi 2 + RT

The values given are the maximum absolute difference between the value at the end of a specified time interval after the mid-level
crossing of the step, and the value one second after the mid-level crossing of the step, expressed as a percentage of the step am-
plitude.

400

BW (MHz)

2

gen

Table 1-14: Typical Characteristics — Time Base System

Name Description

Aperture Uncertainty <5 ps @ <250 ns/div

<50 ps @ >500 ns/div

Table 1-15: Typical Characteristics —

Triggering System

Name Description

Accuracy, Trigger Level or Threshold,

DC Coupled

Input, Auxiliary Trigger

Trigger Marker Position, Edge
Triggering

Holdoff, Variable, Main Trigger

Lowest Frequency for Successful Op-

eration of "Set Level to 50%" Function

Trigger Accuracy

Source

±(2% x | Setting - Net Offset| + 0.2 div x

Any Channel | Volts/div Setting | + Offset Accuracy)

±

:(6% x | Setting | + 8% of p-p signal +

Auxiliary

100 mV)

The input resistance is >1.5 kO; the maximum safe input voltage

is ±20 V (DC + peak AC).

Acquisition Mode

Sample, Average

Envelope

Trigger-Position Error1,

±(1 WI + 1 ns)

±(2 WI + 1 ns)

2

Minimum: For any horizontal scale setting, the minimum holdoff for

a 1x or 5x setting is 10times that setting, but is never shorter than

1 ps or longer than 5 s. The minimum holdoff for a 2.5x setting is 8

times that setting.

Maximum: For any horizontal scale setting, the maximum holdoff is

at least 2 times the minimum holdoff for that setting, but is never

longer than 10 times the minimum holdoff for that setting.

50 Hz

1-20 Specifications

Table 1-15: Typical Characteristics — Triggering System (Cont.)

Typical Characteristics

Name

Sensitivity, Edge Trigger, Not DC
Coupled

Sensitivities, Logic Trigger/Pulse Trig-
ger/Events Delay, DC Coupled

3

4

Sensitivities, Pulse-Type Runt Trigger

Sensitivities, Pulse-Type Trigger Width
and Glitch

6

Description

Trigger Source Typical Signal Level for

Stable Triggering

AC Same as the DC-coupled limits for fre-

quencies above 60 Hz. Attenuates sig-
nals below 60 Hz.

Noise Reject Three and one-half times the DC-coupled

limits.

High Frequency Reject One and one-half times the DC-coupled

limits from DC to 30 kHz. Attenuates sig-
nals above 30 kHz.

Low Frequency Reject One and one-half times the DC-coupled

limits for frequencies above 80 kHz. At-

tenuates signals below 80 kHz.

1.0 division, from DC to 100 MHz with a minimum slew rate of

25 divs/|is at the trigger level or the threshold crossing.

5

1.0 division, from DC to 200 MHz with a minimum slew rate of

25 divs/|is at the trigger level or the threshold crossing.

1.0 division, with a minimum slew rate of 25 divs/|is at the trigger
level or the threshold crossing. For <5 nsec pulse width or rearm

time, 2 divisions are required.

Width, Minimum Pulse and Rearm, for

Logic Triggering or Events Delay

7

Sync Width (Option 05 Video Trigger)

Sync Duty Cycle

5 ns

min. 400 ns for HDTV signals

min. 50 to 1

(Option 05 Video Trigger)

Hum Rejection
(Option 05 Video Trigger)

NTSC and PAL: -20 dB without any trigger spec deterioration.

Triggering will continue down to 0 dB with some performance dete-

rioration.

1 The trigger position errors are typically less than the values given here. These values are for triggering signals having a slew rate

at the trigger point of > 2 division/ns.

2 The waveform interval (Wl) is the time between the samples in the waveform record. Also, see the footnote for the characteristics

Sample Rate Range or Interpolated Waveform Rates in Table 1-3, on page 1-10.

3 The minimum sensitivity for obtaining a stable trigger. A stable trigger results in a uniform, regular display triggered on the se-

lected slope. The trigger point must not switch between opposite slopes on the waveform, and the display must not "roll" across
the screen on successive acquisitions. The TRIG'D LED stays constantly lighted when the SEC/DIV setting is 2 ms or faster but
may flash when the SEC/DIV setting is 10 ms or slower.

4 The minimum signal levels required for stable logic or pulse triggering of an acquisition, or for stable counting of a DC-coupled,

events-delay signal. Also, see the footnote for Sensitivity, Edge-Type Trigger, DC Coupled in this table. (Stable counting of events is
counting that misses no events.)

5 The minimum signal levels required for stable runt pulse triggering of an acquisition. Also, see the footnote for Sensitivity, Edge-

Type Trigger, DC Coupled in this table. (Stable counting of events is counting that misses no events.)

6 The minimum signal levels required for stable pulse width or glitch triggering of an acquisition. Also, see the footnote for Sensitiv-

ity, Edge-Type Trigger, DC Coupled in this table. (Stable counting of events is counting that misses no events.)

7 The minimum pulse width and rearm width required for logic-type triggering or events delaying to occur.

TDS 620A, 640A, & 644A Service Manual

1-21

Typical Characteristics

Table 1-16: Typical Characteristics — Data Handling and Reliability

Name

Time, Data-Retention, Nonvolatile 5 years

Memory1,

2

Description

Floppy disk 3.5 inch, 720 K or 1.44 Mbyte, DOS 3.3-or-later compatible

1 The times that reference waveforms, stored setups, and calibration constants are retained when there is no power to the oscillo-

scope.

2 Data is maintained by small lithium-thionyl-chloride batteries internal to the memory ICs. The amount of lithium is so small in these

ICs that they can typically be safely disposed of with ordinary garbage in a sanitary landfill.

1-22

Specifications

Using this Manual

This section contains information needed to properly use this manual to
service the TDS 620A, 640A, & 644A Digitizing Oscilloscopes, as well as
general information critical to safe and effective servicing of this oscillo-
scope.

Before Servicing This manual is for servicing the TDS 620A, 640A, & 644A Digitizing

Oscilloscopes. To prevent injury to yourself or damage to the oscilloscope,
do the following before you attempt service:

• Be sure you are a qualified service person;

• Read the Safety Summary found at the beginning of this manual;

• Read Strategy for Servicing and Supplying Operating Power in this
section.

When using this manual for servicing, be sure to heed all warnings, cau-
tions, and notes.

Strategy for
Servicing

Throughout this manual, any field-replaceable component, assem-

bly, or part of this oscilloscope is referred to generically as a module.

This manual contains all the information needed for periodic maintenance of
the TDS 620A, 640A, & 644A Digitizing Oscilloscopes. (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 procedures, diagrams, and other trouble-

shooting aids help isolate failures to a specific module, rather than to com-

ponents ofthat module. Once a failure is isolated, replace the module with a

fresh unit obtained from the factory.

All modules are listed in Section 10, Mechanical Parts List. To isolate a failure
to a module, use the fault isolation procedures found in Section 6, Mainte-
nance Information. To remove and replace any failed module, follow the

instructions in Removal and Installation Procedures, also found in Section 6.

TDS 620A, 640A, & 644A Service Manual

1-45

Using this Manual

Manual Structure This manual is divided into sections, such as Specification and Theory of

Operation. Further, it is divided into subsections, such as Product Descrip-
tion and Removal and Installation Procedures.

Sections containing procedures also contain introductions to those proce-
dures. Be sure to read these introductions because they provide information

needed to do the service correctly and efficiently. The following is a brief

description of each manual section.

• Specification — contains a product description of the TDS 620A, 640A,
& 644A Digitizing Oscilloscopes and tables of the characteristics and
descriptions that apply to it.

• Operating Information — is this section. It includes a description of how
this manual is structured, as well as general information and operating

instructions at the level needed to safely power on and service this

oscilloscope. A statement of the service strategy that this manual sup-

ports, and instructions for shipment of the Digitizing Oscilloscopes are

found in this section.

• Theory of Operation — contains circuit descriptions that support general
service and fault isolation.

• Performance Verification — contains a collection of procedures for
confirming that this Digitizing Oscilloscopes functions properly and

meets warranted limits.

• Adjustment Procedures — contains a collection of procedures for adjust-

ing these Digitizing Oscilloscopes to meet warranted limits.

• Maintenance — contains information and procedures for doing preven-
tive and corrective maintenance of these Digitizing Oscilloscopes. In-
structions for cleaning, for module removal and installation, and for fault

isolation to a module are found here.

• Options — contains information on servicing any of the factory-installed
options that may be present in your oscilloscope.

• Electrical Parts List — contains a statement referring you to Replaceable
Parts, where both electrical and mechanical modules are listed. See

below.

• Diagrams — contains a block diagram and an interconnection diagram

useful for isolating failed modules.

• Mechanical Parts List — includes a table of all replaceable modules,
their descriptions, and their Tektronix part numbers.

2-2 Operating Information

Using this Manual

Manual Conventions This manual uses certain conventions which you should become familiar

with before doing service.

Modules

Throughout this manual, any replaceable component, assembly, or part of
this Digitizing Oscilloscopes is referred to generically as a module. In gener-
al, 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, each chassis part of the oscilloscope is a module.

Safety

Symbols and terms related to safety appear in the Safety Summary found at
the beginning of this manual.

Symbols

Besides the symbols related to safety, this manual uses the following sym-
bols:

The "stop sign" icon labels information which must be 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 proce-
dures to help identify certain readouts and menu functions on
screen.

TDS 620A, 640A, & 644A Service Manual 2-3

Using this Manual

Tektronix Service Tektronix provides service to cover repair under warranty as well as other

services that may provide a cost-effective answer to your service needs.

Whether providing warranty repair service or any of the other services listed

below, Tektronix service technicians, trained on Tektronix products, are best
equipped to service your TDS 620A, 640A, & 644A Digitizing Oscilloscopes.
Tektronix technicians are appraised of the latest information on improve-

ments to the product as well as the latest new options to the product.

Warranty Repair Service

Tektronix warrants this product for three years from date of purchase, ex-
cluding probes for which the warranty is one year. (The warranty appears on
the back of the title page in this manual.) Tektronix technicians provide
warranty service at most Tektronix service locations worldwide. Your Tektro-

nix product catalog lists all service locations worldwide.

Repair or Calibration Service

The following services may be purchased to tailor repair and/or calibration of
your TDS 620A, 640A, & 644A Digitizing Oscilloscopes to fit your require-

ments.

Option 95 — With this option, Tektronix ships a calibration data report with
the instrument.

Option 96 — With this option, Tektronix ships a Certificate of Calibration.
This certificate states the instrument meets or exceeds all warranted specifi-
cations and has been calibrated using standards and instruments whose
accuracies are traceable to the National Institute of Standards and Technolo-
gy, an accepted value of a natural physical constant, or a ratio-calibration
technique. The calibration is in compliance with US MIL-STD-45662A. This
option includes a test data report for the oscilloscope.

At-Depot Service — Tektronix offers several standard-priced adjustment

(calibration) and repair services:

• A single repair and/or adjustment.

• Calibrations using equipment and procedures that meet the traceability
standards specific to the local area.

• Annual maintenance agreements that provide for either calibration and

repair or calibration only of the oscilloscope.

Of these services, the annual maintenance agreement offers a particularly
cost-effective approach to service for many owners of the TDS 620A, 640A,
& 644A Digitizing Oscilloscopes. Such agreements can be purchased to
span several years.

2-2 Operating Information

Using this Manual

Self Service

Tektronix supports repair to the module level by providing Module Exchange
and Module Repair and Return.

Module Exchange — This service reduces down time for repair by allow-

ing you to exchange most modules for remanufactured ones. Tektronix ships
you an updated and tested exchange module from the Beaverton, Oregon
service center, typically within 24 hours. Each module comes with a 90-day
service warranty.

Module Repair and Return — This service returns to you within 10 days
the same module that you shipped to Tektronix. The module shipped is

repaired, tested, and returned to you from the Beaverton, Oregon service
center. It is not updated to match current modules of the same type. Again,
each module comes with a 90-day service warranty.

For More Information — Contact your local Tektronix service center or
sales engineer for more information on any of the repair or adjustment
services just described.

Finding Other

Information

Each of the TDS 620A, 640A, & 644A Digitizing Oscilloscopes comes with
the following manuals:

TDS 620A, 640A, & 644A User Manual contains a tutorial to quickly show you

how to operate the TDS 620A, 640A, & 644A Digitizing Oscilloscopes and an

in depth discussion of how to more completely use their features. Applica-
tions are also discussed.

TDS 500A and TDS 600A Reference contains a brief overview of oscilloscope
operation.

TDS 500A and TDS 600A Programmer Manual contains information for pro-
grammed operation via the GPIB interface. Included is the complete com-

mand set, set up information, and programming examples.

TDS 620A, 640A, & 644A Service Manual 2-3

Using this Manual

2-2 Operating Information

General Information

Supplying Operating ^^^ Read all information and heed all warnings in this subsection before
Power

connecting the TDS 620ni 640ni & 644n Digitizing Oscilloscobes to
a bower source.

WARNIN^

AC POWER SOURCE AND CONNECTION. The TDS 620ni 640ni &

644n Digitizing Oscilloscobes operate from a single-phase power

source. It has a three-wire power cord and two-pole, three-terminal

grounding type plug. The voltage to ground (earth) from either pole

of the power source must not exceed the maximum rated operating

voltage, 250 volts.

Before making connection to the power source, be sure the

digitizing oscilloscope has a suitable two-pole, three-terminal

grounding-type plug.

GROUNDING. This instrument is safety Class 1 equipment (IEC

designation). All accessible conductive parts are directly

connected through the grounding conductor of the power cord to

the grounded (earthing) contact of the power plug.

TDS 620A, 640A, & 644A Service Manual

WARNING

The power input plug must be inserted only in a mating receptacle

with a grounding contact where earth ground has been verified by a

qualified service person. Do not defeat the grounding connection.

Any interruption of the grounding connection can create an electric

shock hazard.

For electric shock protection, the grounding connection must be

made before making connection to the instrument's input or output

terminals.

1-51

General Information

Power Cord Information

A power cord with appropriate plug configuration is supplied with each
TDS 620A, 640A, & 644A Digitizing Oscilloscopes. Table 2-1 gives the
color-coding of the conductors in the power cord. If you require a power
cord other than the one supplied, refer to Figure 2-1, Power Cord Plug

Identification.

Table 2-1: Power-Cord Conductor Identification

Conductor Color Alternate Color

Ungrounded (Line)

Grounded (Neutral)

Brown Black

Light Blue

White

Grounded (Earthing) Green/Yellow Green

Option A4*

North American

230V

2-10

Option A5

Switzerland

230V

* Canadian Standards Association certification

includes these power plugs for use in the
North American power network

Figure 2-1: Power-Cord Plug Identification

Option 1A*

North American

115V/High Power

Option 1B

North American

3-Phase

Operating Information

General Information

Operating Voltage

This oscilloscope operates with any line voltage from 90-250 VACRMS with
any line frequency from 47-63 Hz. There are two fuses, either of which may

be used throughout the line voltage and frequency ranges. (The two fuses
are not totally interchangeable as each requires a different fuse cap.)

Memory Backup Power

Memory modules with on-board batteries allow the TDS 620A, 640A, &
644A Digitizing Oscilloscopes to retain some types of data upon loss of the
AC power source. The stored adjustment constants, saved front-panel
settings, current front-panel settings (instrument status), and waveforms
saved in memory are retained.

The on-board batteries of the memory modules have a shelf life of about five
years. Partial or total loss of stored settings upon power on may indicate that
the memory modules need to be replaced.

Operating The following environmental requirements are provided to ensure proper
Environment operation and long instrument life.

Operating Temperature

The TDS 620A, 640A, & 644A Digitizing Oscilloscopes can be operated
where the ambient air temperature is between 0° C and +50° C and can be
stored in ambient temperatures from -40° C to +75° C. After storage at
temperatures outside the operating limits, allow the chassis to stabilize at a
safe operating temperature before applying power.

Ventilation Requirements

The TDS 620A, 640A, & 644A Digitizing Oscilloscopes are cooled by air
drawn in and exhausted through its cabinet side panels by an internal fan.
To ensure proper cooling of the instrument, allow at least two inches
clearance on both sides and 3/4 inch on the bottom of the Digitizing
Oscilloscopes. (The feet on the bottom of the oscilloscope provide the

required clearance when set on flat surfaces.) The top of the oscilloscope
does not require ventilation clearance.

I CAUTION I

If air flow is restricted, the Digitizing Oscilloscopes's power supply

may temporarily shut down.

TDS 620A, 640A, & 644A Service Manual 2-11

General Information

Applying and

Interrupting Power

Consider the following information when you power on or power off the

instrument, or when power is interrupted due to an external power failure.

Power On

Upon power on, the oscilloscope runs its power-on self check. If it passes,
the oscilloscope displays a "passed" status message and a prompt to press
CLEAR MENU to continue. If it fails, the oscilloscope displays a diagnostic

log that identifies the area(s) that failed and a prompt to press CLEAR MENU
to continue. See Section 6, Maintenance, for information on diagnostics and
fault isolation.

DO NOT power off the oscilloscope when either running a signal

path compensation or when doing any of the adjustments de-

scribed in Section 5, Adjustment Procedures. To do so might result

in the loss of internally stored adjustment constants.

In general, do not power off the instrument when doing operations that
affect the data types listed in Table 2-2. Wait for the instrument to finish the
operation when doing adjustments, saving waveforms, or saving setups.

Improper power off or unexpected loss of power to the oscilloscope can

result in the following corruptions of non-volatile RAM (NVRAM). The
following table describes the messages displayed when power is restored
after an abnormal power off.

Table 2-2: Effects of Corrupted Data

Corrupted Data Type Results

Adjustment Constants:

• Signal Path Compensation A signal path compensation is required.

• Voltage Reference

• Frequency Response A frequency response adjustment is

Error Log

Reference Waveforms

A voltage reference adjustment is re-
quired (Section 5).

required (Section 5).

Errors logged are lost.

Waveform Lost.

2-10

Saved Setups Setup Lost.

Operating Information

General Information

Repackaging

Instructions

Use a corrugated cardboard shipping carton having a test strength of at

least 275 pounds and with an inside dimension at least six inches greater
than the instrument dimensions.

If the instrument is being shipped to a Tektronix Service Center, enclose the
following information: the owner's address, name and phone number of a
contact person, type and serial number of the instrument, reason for

returning, and a complete description of the service required.

Seal the shipping carton with an industrial stapler or strapping tape.

Mark the address of the Tektronix Service Center and also your own return
address on the shipping carton in two prominent locations.

Installed Options ^our instrument may be equipped with one or more instrument options.

Except for the line-cord options described by Table 2-1 (on page 2-8 of this
section), all options and optional accessories are listed and described in
Section 7, Options. For further information and prices of instrument options,
see your Tektronix Products catalog or contact your Tektronix Field Office.

TDS 620A, 640A, & 644A Service Manual

2-11

General Information

2-10 Operating Information

General Operating Instructions

Before doing service, read the following operating instructions. These in-
structions are at the level appropriate for servicing this Digitizing
Oscilloscopes. The complete operator's instructions are found in the User

Manual.

Additional instructions are integrated into the service procedures found in

later sections of this manual. For instance, the procedures found in the
section Performance Verification contain instructions for making the front-pa-

nel settings required to check each instrument characteristic included there.
Also, the general instructions for operating this Digitizing Oscilloscopes's

internal diagnostic routines are found in Section 6, Maintenance. You may
also find the Product Description in Section 1 useful for understanding how
the oscilloscope functions.

Screen Layout

Basic Procedures

The screen layout is illustrated in Figure 2-2 on page 2-14. Note that the
figure illustrates a full graticule; you may also select a grid, crosshair, or
frame graticule from the display menu.

How to Power On

Push the principal power switch found on the rear panel of the Digitizing
Oscilloscopes, then push the ON/STBY (standby) switch to toggle the

Digitizing Oscilloscopes into operation. The switch at the rear panel is the
true power disconnect switch. The ON/STBY(standby) switch simply toggles
operation on and off.

WARNING

The principal power switch at the rear panel is the true power

disconnect switch. The ON/STBY (standby) switch simply toggles

operation on and off. When connected to a power source and when

the principal power switch is on, the internal power supplies and

much of the other circuitry of this Digitizing Oscilloscopes are
energized regardless of the setting of the ON/STBY switch.

TDS 620A, 640A, & 644A Service Manual 1-57

General Operating Instructions

Brief status

information.

Graticule and waveforms

Position of waveform

record relative to General purpose

the screen and display. knob readout.

Waveform reference
symbols: ground levels
and waveform sources.

Vertical scale,

horizontal scale, and

trigger level readouts.

Pop-up menu

Set to TTL

Set to ECL

ms

Slope

a

Main menu display area. Readouts in

lower graticule area move here when

CLEAR MENU is pressed.

c

a

Side menu area. Readouts
for measurements move
here when CLEAR MENU
is pressed.

Figure 2-2: Map of Display Functions

How to Use Help

Push the HELP front-panel button to enter help mode. Front-panel knobs

and buttons now display information about their function when turned or

pushed. Push HELP again to exit help mode.

To get help information on a menu item, display the menu desired (if you are

in help mode, exit help first). Push HELP Now the menu buttons display
information about their function when pushed.

How to Use the Status Menu

Push the SHIFT, then the STATUS front-panel buttons to display the status
menu. You will find messages reflecting the state of the acquisition system,

whether it is running or stopped (and if it is stopped, why), as well as setup-

related information.

2-14 Operating Information

General Operating Instructions

How to Set Functions

Most functions can be set either by using one (or two) front-panel button(s)
or knob(s), or by pushing a front-panel button to use a main menu, and then
a side-menu button to set the function. The following steps illustrate both

procedures.

1. Locate the block that contains the function to be set.

Special Function Controls:

Access all functions except

vertical, horizontal, and

trigger functions from this

front-panel control block.

Vertical Function Controls:

Access all vertical functions

and inputs from this front-panel

control block.

Q

STATUS

HELP

/-SAVE/RECALL-«

WAVEFORM

( >

SETUP

)

iV—>

(

(

AUTOSET

(

I a

APPLICATION

MEASURE CHÄi

Horizontal Function
Controls: Access all

horizontal functions from

this front-panel block.

JTIUTY

DISPLAY

I HORIZONTAL ^

^IpnsrnnNb

Trigger Function Controls:
Access all trigger functions
from this front-panel block.

M

El cd CD

D

a

A

CD B CD c CD

(CLR)

PROBE COMPENSATION

m

k

n

CD (±)

CD

(±)

ENTER

X

0

(3

TDS 620A, 640A, & 644A Service Manual 2-19

General Operating Instructions

2. Select the waveform source(s). Position, scale, and set trigger level for
waveform source(s) directly from the front-panel. (Examples of possible
control selections are given in the steps that follow.)

1 2 3 4

2-14

a. Input waveforms into these channels (7). Example: CH 1.

b. Push any channel's button (8) to display its waveform. The last

channel turned on determines which waveform is positioned and
scaled. The indicator above the channel last selected is lighted.

Example: Push CH 1; then CH 2.

c. Vertically (1) and horizontally (2) scale and position the waveform(s)

selected. Example: Set the scale to 100 mV/div and center the
waveform on screen.

d. Stop and start acquiring waveforms (3). Example: Push RUN/STOP

if not acquiring.

e. Adjust trigger level (6) to trigger the waveform(s) selected or use

these buttons (5) to either set a trigger level at the mid-amplitude

level of the selected waveform or to force a single trigger. Example:
Push SET LEVEL TO 50%.

Operating Information

General Operating Instructions

3. Set all other functions using menus.

a. Choose the waveform source (8) first if setting a vertical function;

else skip to step b. Example: Push CH 2.

b. Push SHIFT (4) if the function to be set is highlighted in blue; else

skip to step c.

TDS 620A, 640A, & 644A Service Manual

c. Push the front-panel button that corresponds to the menu contain-

ing the function. A main menu (14) for selecting among related

functions appears. Example: Push VERTICAL MENU.

Note the two labels: the top label is a function to choose from; the
bottom label tells you the current setting for that function. Offset is

currently set to OV.

d. Select a function from the main menu using the main-menu but-

tons (12). A side menu for selecting among that the available set-
tings for that function appears. Example: Push Coupling (13).

e. Select the setting for the function from the side menu (9) using the

side-menu buttons (11). Example: Push AC (10).

2-19

General Operating Instructions

How to Set Complex Functions

A few functions require more than just two levels (main and side) of menus
to completely specify their settings. In such cases, either the main menu, the
side menu, or both are modified to supply additional choices. The proce-
dures that follow show both schemes.

1. Set up a function using pop-up menus:

a. For some selections, pushing a main-menu button pops up a menu

(18) of subfunctions. Example: Push Type (17).

Note the pop-up menu for Type is set to Edge. All the main-menu
buttons to the right of the pop-up menu are labeled with subfunc-

tions of Edge.

b. Pushing the button that popped up the menu (17) toggles through

the pop-up menu choices. Example: Repeatedly push Type to
toggle through the pop-up menu. Notice the other main-menu

button labels change accordingly. Toggle back to Edge.

c. Complete the setting of the desired mode by selecting from the

main menu and the side menu that results. Example: Push Mode &
Holdoff (16), and then push Normal (15).

2-14

Operating Information

2. Set up a function using the general purpose knob (20). (The examples
of possible menu selections in the substeps that follow assume you've

pushed TRIGGER MENU.)

Stopped: 29898 Acquisitions Trigger Level:

General Operating Instructions

ECL

Set

Will ^ Oil 111 V

M 5.00MS Chi I 20mV

Source Coupling Slope

21

a. Pushing some main-menu buttons displays a side menu with labels

containing readouts that can be varied. Example: Push Level (21).

b. Pushing the side-menu button Level assigns the general purpose

knob to control the readout appearing in the button label. It also

copies the readout to the general purpose knob readout area in the

right corner of the screen. Example: Push Level (19).

c. Use the general purpose knob (20) to adjust the trigger level to the

setting desired. Example: Turn the knob to -20 mV.

More About the General Purpose Knob — As you've just seen, the

general purpose knob can be used to extend the number of choices avail-
able to a side menu button. The general purpose knob can also be as-
signed to control the following functions:

• Cursor positioning

• Display intensities

• Delay time

• Gated measurements

• Number of events

• Template generation

TDS 620A, 640A, & 644A Service Manual

2-19

General Operating Instructions

• Trigger position

• Holdoff

• Offset

• Variable persistence

In all cases, the menus are used to select the function to which the general
purpose knob is assigned. The following attributes apply to this knob:

• Depending on the function it is assigned to control, the general purpose
knob may vary numerical readouts, position objects (cursors) on screen,

or select between icon-label settings that show up in side-menu labels.

• The general purpose knob has a readout area at the upper right corner

of the screen. (See Figure 2-2.) This readout always reflects the name
and value of the function that the general purpose knob is currently
controlling.

• Whenever the general purpose knob assignment is changed, a knob
icon appears immediately to the left of the general purpose knob read-

out to notify you of the assignment change. The icon is removed as
soon as you use the general purpose knob to change the value of the
function it is assigned to.

• To assign the general purpose knob to control a function, display the
menu containing the function; then select the function. (Note that not all

functions can be controlled by the general purpose knob.)

• Whenever the menu is removed, the general purpose knob is not as-

signed and doesn't control any function. (An exception is the cursor
function. If cursors are turned on, removing the menu leaves the knob
assigned to control the cursors until reassigned by selecting another

menu and function that uses the knob.)

• When the SHIFT button is lit, the general purpose knob becomes a
coarse adjustment. When the SHIFT button is not lit, the general pur-
pose knob becomes a fine adjustment.

• The general purpose knob also has a SELECT button. This button is
used to toggle the knob between the control of either of the two cursors
displayed when H-bar or V-bar cursors are turned on in the cursor
menu.

Display and Utility Menus — Using the techniques described for using
menus, you can access and change functions in the display menu and
utilities menu. In the Display menu, you can set the following functions:

• Color: waveforms, readouts, graticule.

2-14

• Intensity: waveforms, readouts, graticule, etc.

• Style of waveform display(s): vectors or dots, intensified or non-intensi-

fied samples, and infinite or variable persistence.

• Display format: XY or YT.

Operating Information

General Operating Instructions

• Graticule format: type.

• Waveform interpolation filter and readout options.

From the Utility menu, you can configure the GPIB port (talk/listen, address,

etc.) and access internal routines for self diagnostics and self compensation.

Instructions for setting up communication over the GPIB are found in Sec-

tion5, Adjustment Procedures.

TDS 620A, 640A, & 644A Service Manual

2-21

General Operating Instructions

2-22 Operating Information

Circuit Description

This section describes the electrical operation of TDS 620A, 640A, &
644A Digitizing Oscilloscopes using the major circuit blocks or modules.

This section has two main parts:

• Logic Conventions describes how logic functions are discussed and
represented in this manual.

• Module Overview describes circuit operation from a functional-circuit
block perspective.

Logic Conventions TDS 620A, 640A, & 644A Digitizing Oscilloscopes contain many digital logic

circuits. This manual refers to these circuits with standard logic symbols and
terms. Unless otherwise stated, all logic functions are described using the

positive-logic convention: the more positive of the two logic levels is the high

(1) state, and the more negative level is the low (0) state. Signal states may
also be described as "true" meaning their active state or "false" meaning
their non-active state. The specific voltages that constitute a high or low
state vary among the electronic devices.

Active-low signals are indicated by a tilde prefixed to the signal name

(PRESET). Signal names are considered to be either active-high, active-low,
or to have both active-high and active-low states.

Module Overview This module overview describes the basic operation of each functional

circuit block as shown in Figure 9-1 on page 9-2.

General

TDS 620A, 640A, & 644A Digitizing Oscilloscopes have four-channels. Each
channel provides a calibrated vertical scale factor. All of the four channels
can be simultaneously acquired at the maximum digitizing rate of 2 GSam-

ples/sec.

Input Signal Path

A signal enters the oscilloscope through a probe connected to a BNC on the
A15 Attenuator board.

TDS 620A, 640A, & 644A Service Manual 4-1

Circuit Description

Attenuators — Circuitry in the attenuator selects the input coupling, termi-

nation, and the attenuation factor. The processor system, by way of the
acquisition system, controls the attenuators. For example, if 50 Q input
termination is selected and the input is overloaded, the processor system
switches the input to the 1 MQ position.

Probe Coding Interface — Probe coding interface signals pass through
the A15 Attenuator to the acquisition system, where they are sensed and
controlled.

Acquisition System — The acquisition system amplifies the input signals,
samples them, converts them to digital signals, and controls the acquisition

process under direction of the processor system. The acquisition system

includes the trigger, acquisition timing, and acquisition mode generation and
control circuitry.

D1 Bus — The acquisition system passes the digital values representing
the acquired waveform through the A14 D1 Bus to the A11 DRAM Proces-
sor/Display board. This happens after a waveform acquisition is complete if
the digital signal processor in the processor system requests the waveform.

Processor System —The processor system contains a 68020 micropro-
cessor that controls the entire instrument. It includes the firmware. It also

includes a GPIB interface. You can reprogram the firmware from a remote
controller using the GPIB and an external software package.

The processor also includes a digital signal processor. This signal processor

processes each waveform as directed by the system processor. Waveforms
and any text to be displayed are passed on to the display system. The A11

DRAM Processor/Display board contains both the processor and display
systems.

Display System — Text and waveforms are processed by different parts of
the display circuitry. The display system sends the text and waveform infor-

mation to the tube assembly as a video signal. The display system also
generates and sends vertical (VSYNC) and horizontal (HSYNC) sync signals
to the tube assembly. A VGA-compatible video output is at the rear of the
TDS 644A.

Voltage Controlled Oscillator (VCO)

Master clocks for the acquisition system are generated by the circuitry on
the A10 Acquisition board. The circuitry makes up a phased locked loop.
The master clock is divided down by the A10 Acquisition circuitry under
control of the processor system.

3-2

Theory of Operation

Circuit Description

Tube Assembly

All information (waveforms, text, graticules, and pictographs) is displayed by
the A30/31/32 Display system. The A30 generates the high voltages neces-
sary to drive the display tube. It also contains the video amplifier, horizontal
oscillator, and the vertical and horizontal yoke driver circuitry.

Front Panel

The processor system sends instructions to and receives information from
the Front Panel Processor on the A12 Front Panel board. The Front Panel

Processor reads the front-panel switches and potentiometers. Any changes

in their settings are reported to the processor system. The Front Panel

Processor also turns the LEDs on and off and generates the bell signal.

Front-panel menu switches are also read by the Front Panel Processor. The

processor sends any changes in menu selections to the processor system.
The ON/STBY switch is one of the menu switches. However, it is not read by
the Front Panel Processor, but passes through the A12 Front Panel board
and the A11 DRAM Processor/Display board to the low voltage power sup-

ply.

The front panel also generates the probe compensation signals SIGNAL
and GND.

Rear Panel

The GPIB connector provides access to stored waveforms, and allows
external control of the oscilloscope.

You can make hardcopies on the GPIB, RS-232 and Centronics ports.

Low Voltage Power Supply

The low voltage power supply is a switching power converter with active

power factor control. It supplies power to all of the circuitry in the oscillo-
scope.

The principal POWER switch, located on the rear panel, controls all power
to the oscilloscope including the Low Voltage Power Supply. The ON/STBY
switch, located on the front panel, also controls all of the power to the oscil-

loscope except for part of the circuitry in the Low Voltage Power Supply.

The power supply sends a power fail (~PF) warning to the processor sys-
tem if the power is going down.

Fan

The fan provides forced air cooling for the oscilloscope. It connects to +25 V
from the Low Voltage Power Supply by way of the A11 DRAM Processor/Dis-

play module.

TDS 620A, 640A, & 644A Service Manual 3-3

Circuit Description

3-4 Theory of Operation

Brief Procedures

The Self Tests use internal routines to confirm basic functionality and proper
adjustment. No test equipment is required to do these test procedures.

The Functional Tests utilize the probe-compensation output at the front panel
as a test-signal source for further verifying that the oscilloscope functions

properly. A standard-accessory probe, included with this oscilloscope, is the
only equipment required.

General Instructions Besides the Brief Procedures, the set of procedures that can be used to

verify oscilloscope performance includes the Performance Tests, found later

in this section. You may not need to perform all of these procedures, de-

pending on what you want to accomplish:

• To rapidly confirm that the oscilloscope functions and was adjusted
properly, just do the procedures under Self Tests, which begin on
page 4-4.

Advantages: These procedures are quick to do, require no external
equipment or signal sources, and perform extensive functional and
accuracy testing to provide high confidence that the oscilloscope will

perform properly. They can be used as a quick check before making a

series of important measurements.

• To further check functionality, first do the Self Tests just mentioned; then

do the procedures under Functional Tests that begin on page 4-6.

Advantages: These procedures require minimal additional time to

perform, require no additional equipment other than a standard-acces-

sory probe, and more completely test the internal hardware of the oscil-

loscope. They can be used to quickly determine if the oscilloscope is

suitable for putting into service, such as when it is first received.

• If more extensive confirmation of performance is desired, do the Per-

formance Tests, beginning on page 4-13, after doing the Functional and
Self Tests just referenced.

Advantages: These procedures add direct checking of warranted
specifications. They require more time to perform and suitable test
equipment is required. (See Equipment Required beginning on

page 4-14.)

If you are not familiar with operating this oscilloscope, read the TDS 500A &
TDS 600A Reference or the TDS 620A, 640A, & 644A User manual. These
contain instructions that will acquaint you with the use of the front-panel
controls and the menu system.

TDS 620A, 640A, & 644A Service Manual

4-1

Brief Procedures

Conventions Throughout these procedures the following conventions apply:

• Each test procedure uses the following general format:

Title of Test

Equipment Required

Prerequisites

Procedure

• Each procedure consists of as many steps, substeps, and subparts as
required to do the test. Steps, substeps, and subparts are sequenced

as follows:

1. First Step

a. First Substep

• First Subpart

• Second Subpart

b. Second Substep

2. Second Step

• In steps and substeps, the lead-in statement in italics instructs you what

to do, while the instructions that follow tell you how to do it, as in the
example step below, "Initialize the oscilloscope" by doing "Press save/

recall SETUP! Now, press the main-menu button...".

Initialize the oscilloscope: Press save/recall SETUP. Now, press the

main-menu button Recall Factory Setup; then the side-menu
button OK Confirm Factory Init.

• Where instructed to use a front-panel button or knob, or select from a
main or side menu, or verify a readout or status message, the name of

the button or knob appears in boldface type: "press SHIFT; then UTIL-

ITY", "press the main-menu button System" until Cal is highlighted in

the pop-up menu. Verify that the status message is Pass in the main

menu under the Voltage Reference label.

The symbol at the left is accompanied by information you must read
to do the procedure properly.

4-2

Performance Verification

Brief Status
Information

Graticule and Waveforms

Brief Procedures

• Refer to Figure 4-1: "Main menu" refers to the menu that labels the

seven menu buttons under the display; "side menu" refers to the menu
that labels the five buttons to the right of the display. "Pop-up menu"

refers to a menu that pops up when a main-menu button is pressed.

Position of Waveform

Record Relative to

the Screen and Display

General Purpose

Knob Readout

Waveform Reference

Symbols: Ground Levels

and Waveform Sources

Vertical Scale, Horizontal

Scale, and Trigger Level

Readouts

Pop-up Menu

set to L

Set to ECL

Side menu area.
Readouts for
measurements
move here when
CLEAR MENU is
pressed.

Main menu display area. Readouts in
lower graticule area move here when

CLEAR MENU is pressed.

Figure 4-1: Map of Display Functions

TDS 620A, 640A, & 644A Service Manual 4-3

Brief Procedures

Self Tests ^his procedure uses internal routines to verify that the oscilloscope functions

and was adjusted properly. No test equipment or hookups are required.

Verify Internal Adjustment, Self Compensation, and

Diagnostics

Equipment Required: None.

Prerequisites: Power on the Digitizing Oscilloscope and allow a 20 minute

warm-up before doing this procedure.

Procedure:

1. Verify that internal diagnostics pass: Do the following substeps to verify
passing of internal diagnostics.

a. Display the System diagnostics menu:

• Press SHIFT; then press UTILITY.

• Repeatedly press the main-menu button System until Diag/Err

is highlighted in the pop-up menu.

b. Run the System Diagnostics:

• First disconnect any input signals from all four channels.

• Press the main-menu button Execute; then press the side-menu
button OK Confirm Run Test.

(J) c. Wait: The internal diagnostics do an exhaustive verification of proper

oscilloscope function. This verification will take up to two minutes. At
some time during the wait, a "clock" icon (shown at left) will appear
on-screen. When the verification is finished, the resulting status will
appear on the screen.

d. Confirm no failures are found: Verify that no failures are found and

reported on-screen.

e. Confirm the three adjustment sections have passed status:

• Press SHIFT; then press UTILITY

• Press the main-menu button System until Cal is highlighted in

the pop-up menu.

• Verify that the word Pass appears in the main menu under the

following menu labels: Voltage Reference, Frequency Re-
sponse, and Pulse Trigger. (See Figure 4-2.)

4-4

Performance Verification

First, the CAL menu is displayed.

Second, the adjustment

sections are verified.

Brief Procedures

compensation is run and is

Third, a signal path

verified.

Figure 4-2: Verifying Adjustments and Signal-Path Compensation

f. Run the signal-path compensation: Press the main-menu button

Signal Path; then press the side-menu button OK Compensate
Signal Paths.

g. Wait: Signal-path compensation runs in about one to two minutes.

While it progresses, a "clock" icon (shown at left) is displayed on-
screen. When compensation completes, the status message will be

updated to Pass or Fail in the main menu (see step h).

h. Confirm signal-path compensation returns passed status: Verify that

the word Pass appears under Signal Path in the main menu. (See

Figure 4-2.)

2. Return to regular service: Press CLEAR MENU to exit the system me-

TDS 620A, 640A, & 644A Service Manual

nus.

4-5

Brief Procedures

Functional Tests The P

tions properly. The only equipment required is one of the standard-accesso-

ry probes and, to check the file system, a 3.5 inch, 720 K or 1.44 Mbyte

floppy disk.

urPose

of these procedures is to confirm that the oscilloscope func-

WARNING

The P6205 probes provide an extremely low loading capacitance

(<2 pF) to ensure the best possible signal reproduction. These

probes should not be used to measure signals exceeding ±10

volts, or errors in signal measurement will be observed. Above 40

volts, damage to the probe may result. To make measurements

beyond ±10 volts, use either the P6139A probe (good to 500 volts),

or refer to the catalog for a recommended probe.

These procedures verify functions; that is, they verify that the oscillo-
scope features operate. They do not verify that they operate within

limits.

Therefore, when the instructions in the functional tests that follow
call for you to verify that a signal appears on-screen "that is about
five divisions in amplitude" or "has a period of about six horizontal
divisions," etc., do NOT interpret the quantities given as limits.
Operation within limits is checked in Performance Tests, which begin
on page 4-13.

DO NOT make changes to the front-panel settings that are not
called out in the procedures. Each verification procedure will require
you to set the oscilloscope to certain default settings before verifying
functions. If you make changes to these settings, other than those
called out in the procedure, you may obtain invalid results. In this
case, just redo the procedure from step 1.

When you are instructed to press a menu button, the button may
already be selected (its label will be highlighted). If this is the case, it

is not necessary to press the button.

4-6 Performance Verification

Brief Procedures

Verify All Input Channels

Equipment Required: One P6139Aor P6205 probe.

Prerequisites: None.

Procedure:

1. Install the test hookup and preset the oscilloscope controls:

Figure 4-3: Universal Test Hookup for Functional Tests

a. Hook up the signal source: Install the probe on CH1. Connect the

probe tip to PROBE COMPENSATION SIGNAL on the front panel;
connect the probe ground to PROBE COMPENSATION GND.

b. Initialize the oscilloscope:

• Press save/recall SETUP

• Press the main-menu button Recall Factory Setup.

• Press the side-menu button OK Confirm Factory Init.

Verify that all input channels operate: Do the following substeps — test
CH 1 first, skipping substep a since CH 1 is already set up for verification

from step 1.

a. Select an unverified channel:

• Press WAVEFORM OFF to remove the channel just verified from

display.

• Press the front-panel button that corresponds to the channel
you are to verify.

• Move the probe to the channel you selected.

TDS 620A, 640A, & 644A Service Manual

b. Set up the selected channel:

• Press AUTOSET to obtain a viewable, triggered display in the
selected channel.

• Set the horizontal SCALE to 250 |is. Press CLEAR MENU to

remove any menu that may be on the screen.

4-7

Brief Procedures

XX • Sample mode displays an actively acquiring waveform on-

c. Verify that the channel is operational: Confirm that the following

statements are true.

• The vertical scale readout for the channel under test shows a
setting of 200 mV, and a square-wave probe-compensation
signal about 2.5 divisions in amplitude is on-screen. (See Fig-

ure 4-1 on page 4-3 to locate the readout.)

• The vertical POSITION knob moves the signal up and down the
screen when rotated.

• Turning the vertical SCALE knob counterclockwise decreases
the amplitude of the waveform on-screen, turning the knob

clockwise increases the amplitude, and returning the knob to

200 mV returns the amplitude to about 2.5 divisions.

d. Verify that the channel acquires in all acquisition modes: Press

SHIFT; then press ACQUIRE MENU. Use the side menu to select, in
turn, each of the three hardware acquire modes and confirm that the
following statements are true. Refer to the icons at the left of each
statement as you confirm those statements.

screen. (Note that there is noise present on the peaks of the
square wave.)

J™ljL • Envelope mode displays an actively acquiring waveform on-

screen with the noise displayed.

• Average mode displays an actively acquiring waveform on-

_TL screen with the noise reduced.

e. Test all channels: Repeat substeps a through d until all four input

channels are verified.

3. Remove the test hookup: Disconnect the probe from the channel input
and the probe-compensation terminals.

Verify the Time Base

Equipment Required: One P6139Aor P6205 probe.

Prerequisites: None.

Procedure:

1. Install the test hookup and preset the oscilloscope controls:

a. Hook up the signal source: Install the probe on CH1. Connect the

probe tip to PROBE COMPENSATION SIGNAL on the front panel;

connect the probe ground to PROBE COMPENSATION GND. (See

Figure 4-3 on page 4-7.)

b. Initialize the oscilloscope:

• Press save/recall SETUP

• Press the main-menu button Recall Factory Setup; then press
the side-menu button OK Confirm Factory Init.

4-8 Performance Verification

Brief Procedures

c. Modify default settings:

• Press AUTOSET to obtain a viewable, triggered display.

• Set the horizontal SCALE to 250 |s.

• Press CLEAR MENU to remove the menus from the screen.

2. Verify that the time base operates: Confirm the following statements.

a. One period of the square-wave probe-compensation signal is about

four horizontal divisions on-screen for the 250 |is horizontal scale
setting (set in step 1c).

b. Rotating the horizontal SCALE knob clockwise expands the wave-

form on-screen (more horizontal divisions per waveform period),
counterclockwise rotation contracts it, and returning the horizontal
scale to 250 |is returns the period to about four divisions.

c. The horizontal POSITION knob positions the signal left and right

on-screen when rotated.

3. Remove the test hookup: Disconnect the probe from the channel input
and the probe-compensation terminals.

Verify the Main and Delayed Trigger Systems

Equipment Required: One P6139Aor P6205 probe.

Prerequisites: None.

Procedure:

1. Install the test hookup and preset the oscilloscope controls:

a. Hook up the signal source: Install the probe on CH 1. Connect the

probe tip to PROBE COMPENSATION SIGNAL on the front panel;

connect the probe ground to PROBE COMPENSATION GND. (See

Figure 4-3 on page 4-7.)

b. Initialize the oscilloscope:

• Press save/recall SETUP

• Press the main-menu button Recall Factory Setup.

• Press the side-menu button OK Confirm Factory Init.

c. Modify default settings:

• Press AUTOSET to obtain a viewable, triggered display.

• Set the horizontal SCALE for the M (main) time base to 250 |is.

• Press TRIGGER MENU.

• Press the main-menu button Mode & Holdoff.

• Press the side-menu button Normal.

• Press CLEAR MENU to remove the menus from the screen.

TDS 620A, 640A, & 644A Service Manual 4-9

Brief Procedures

2. Verify that the main trigger system operates: Confirm that the following
statements are true.

• The trigger level readout for the main trigger system changes with

the trigger-LEVEL knob.

• The trigger-level knob can trigger and untrigger the square-wave
signal as you rotate it. (Leave the signal untriggered, which is indi-
cated by the display not updating.)

• Pressing SET LEVEL TO 50% triggers the signal that you just left

untriggered. (Leave the signal triggered.)

3. Verify that the delayed trigger system operates:

a. Select the delayed time base:

• Press HORIZONTAL MENU.

• Press the main-menu button Time Base.

• Press the side-menu button Delayed Triggerable; then press
the side-menu button Delayed Only.

• Set the horizontal SCALE for the D (delayed) time base to
250 Ms.

b. Select the delayed trigger level menu:

• Press SHIFT; then press DELAYED TRIG.

• Press the main-menu button Level; then press the side-menu

button Level.

c. Confirm that the following statements are true:

• The trigger-level readout for the delayed trigger system changes
as you turn the general purpose knob.

• The general purpose knob can trigger and untrigger the square-
wave probe-compensation signal as you rotate it. (Leave the
signal untriggered, which is indicated by the display not updat-

ing.)

• Pressing the side-menu button Set to 50% triggers the probe-

compensation signal that you just left untriggered. (Leave the

signal triggered.)

d. Verify the delayed trigger counter:

• Press the main-menu button Delay by Time.

• Use the keypad to enter a delay time of 1 second. Press 1, then

press ENTER.

• Verify that the trigger READY indicator on the front panel flashes
about once every second as the waveform is updated on-
screen.

4. Remove the test hookup: Disconnect the standard-accessory probe from
the channel input and the probe-compensation terminals.

4-10 Performance Verification

Brief Procedures

Verify the File System (Optional on TDS 620A and 640A)

Equipment Required: One P6139A or P6205 probe and one 720 K or

1.44 Mbyte, 3.5 inch DOS compatible disk. You can use a disk of your own

or you can use the Programming Examples Software 3.5 inch disk (Tektronix

part number 063-1134-XX) contained in the TDS Family Programmer Manual
(Tektronix part number 070-8709-XX).

Prerequisites: None.

Procedure:

1. Install the test hookup and preset the oscilloscope controls:

a. Hook up the signal source: Install the probe on CH1. Connect the

probe tip to PROBE COMPENSATION SIGNAL on the front panel;

connect the probe ground to PROBE COMPENSATION GND. (See

Figure 4-3 on page 4-7.)

b. Insert the test disk: Insert the disk in the disk drive to the left of the

monitor.

• Position the disk so the metal shutter faces the drive.

• Position the disk so the stamped arrow is on the top right side.
In other words, place the angled corner in the front bottom
location.

• Push the disk into the drive until it goes all the way in and clicks
into place.

c. Initialize the oscilloscope:

• Press save/recall SETUP

• Press the main-menu button Recall Factory Setup.

• Press the side-menu button OK Confirm Factory Init.

d. Modify default settings:

• Press AUTOSET to obtain a viewable, triggered display.

• Set the horizontal SCALE for the M (main) time base to 250 ps
(one click clockwise). Notice the waveform on the display now

shows two and a half cycles instead of five.

• Press CLEAR MENU to remove the menus from the screen.

e. Save the settings:

• Press SETUP

• Press the main-menu button Save Current Setup; then press

the side-menu button To File.

• Turn the general purpose knob to select the file to save. Choose
TEK?????.SET (or fdo:). With this choice, you'll save a file

starting with TEK, then containing 5-numbers, and a .SET

extension. For example, the first time you run this on a blank,

formatted disk or on the Example Programs Disk, the TDS will
assign the name TEK00000.SET to your file. If you ran the

procedure again, the TDS would increment the name and call

the file TEK0

0 0

01.SET.

TDS 620A, 640A, & 644A Service Manual

4-11

Brief Procedures

• Press the side-menu button Save To Selected File.

2. Verify the file system works:

• Press AUTOSET to restore the 500 |s time base and the five cycle

waveform.

• Press the main-menu button Recall Saved Setup; then press the
side-menu button From File.

• Turn the general purpose knob to select the file to recall. For exam-

ple, if you followed the instructions above and used a blank disk,

you had the TDS assign the name TEK00000 . SET to your file.

• Press the side-menu button Recall From Selected File.

• Verify that Digitizing Oscilloscope retrieved the saved setup from the
disk. Do this by noticing the horizontal SCALE for the M (main) time

base is again 250 |is and the waveform shows only two and a half

cycles just as it was when you saved the setup.

3. Remove the test hookup:

• Disconnect the standard-accessory probe from the channel input
and the probe-compensation terminals.

• Remove the disk from the disk drive. Do this by pushing in the tab at
the bottom of the disk drive.

4-12

Performance Verification

Performance Tests

This subsection contains a collection of procedures for checking that the
TDS 620A, 640A, & 644A Digitizing Oscilloscopes perform as warranted.
Since the procedures cover models with both two full-featured channels

(TDS 620A) and four full-featured models (TDS 640A and 644A), instructions
that apply only to one of the model types are clearly identified. Otherwise, all
test instructions apply to both the two and four channel models.

The procedures are arranged in four logical groupings: Signal Acquisition

System Checks, Time Base System Checks, Triggering System Checks, and
Output Ports Checks. They check all the characteristics that are designated

as checked in Section 1, Specifications. (The characteristics that are
checked appear in boldface type under Warranted Characteristics in
Section 1.)

These procedures extend the confidence level provided by the basic

procedures described on page 4-1. The basic procedures should be

done first, then these procedures performed if desired.

Prerequisites

The tests in this subsection comprise an extensive, valid confirmation of

performance and functionality when the following requirements are met:

• The cabinet must be installed on the Digitizing Oscilloscope.

• You must have performed and passed the procedures under Self Tests,
found on page 4-4, and those under Functional Tests, found on

page 4-6.

• A signal-path compensation must have been done within the recom-

mended calibration interval and at a temperature within ±5° C of the
present operating temperature. (If at the time you did the prerequisite

Self Tests, the temperature was within the limits just stated, consider this

prerequisite met.)

• The Digitizing Oscilloscope must have been last adjusted at an ambient
temperature between +20° C and +30° C, must have been operating
for a warm-up period of at least 20 minutes, and must be operating at an
ambient temperature between +4° C and +50° C. (The warm-up re-
quirement is usually met in the course of meeting the first prerequisite

listed above.)

Related Information — Read General Instructions and Conventions that

start on page 4-1.

TDS 620A, 640A, & 644A Service Manual 4-13

Performance Tests

Equipment Required

These procedures use external, traceable signal sources to directly check
warranted characteristics. The required equipment list follows this introduc-
tion.

Table4-1: Test Equipment

Item Number and

Minimum Requirements

Description

1. Attenuator,10X
(three required)

Ratio: 10X; impedance 50 0;
connectors: female BNC in-
put, male BNC output

2. Attenuator, 5X

Ratio: 5X; impedance 50 0;
connectors: female BNC in-
put, male BNC output

Adapter, BNC

3.

BNC female to Clip Leads

female to Clip

Leads

4. Terminator, 50 0 Impedance 50 0; connectors:
female BNC input, male BNC

output

5. Cable, Precision
50 0 Coaxial

50 0, 36 in, male to male BNC
connectors

(two required)

Connector, Du-

6.

Female BNC to dual banana Tektronix part number

al-Banana (two

required)

7. Connector, BNC

Male BNC to dual female BNC

"T"

Example Purpose

Tektronix part number

Signal Attenuation

011-0059-02

Tektronix part number

Signal Attenuation

011-0060-02

Tektronix part number
013-0076-00

Signal Coupling for
Probe Compensator
Output Check

Tektronix part number
011-0049-01

Signal Termination
for Channel Delay
Test

Tektronix part number
012-0482-00

Signal Interconnec-
tion

Various Accuracy

103-0090-00

Tektronix part number

103-0030-00

Tests

Checking Trigger
Sensitivity

8. Coupler, Dual-
Input

Generator, DC

9.

Calibration

10. Generator, Cali-
bration

11. Generator, Lev-

eled Sine Wave,

Medium-Fre-

quency

12. Generator, Lev-

eled Sine Wave,

High-Frequency

4-14

Female BNC to dual male
BNC

Variable amplitude to ±104 V;

accuracy to 0.1%

500 mV square wave calibra-

tor amplitude; accuracy to

0.25%

200 kHz to 250 MHz; Variable
amplitude from 5mV to 4 Vp_p
into 50 0

250 MHz to 500 MHz; Variable
amplitude from 500 mV to
4 V

into 50 0; 6 MHz

p-p

reference

Tektronix part number
067-0525-02

Checking Delay

Between Channels

Data Precision 8200 Checking DC Offset,

Gain, and Measure-

ment Accuracy

Tektronix PG 506A

1

To check accuracy
of the CH 3 Signal
Out

Tektronix SG 503 Leveled Sine
Wave Generator

1

Checking Trigger
Sensitivity at low
frequencies

Tektronix SG 504 Leveled Sine
Wave Generator1 with a TM 500
Series Power Module with SG
504 Output Head

Checking Analog

Bandwidth and Trig-

ger Sensitivity at

high frequencies

Performance Verification

Table4-1: Test Equipment (Cont.)

Performance Tests

Item Number and

Minimum Requirements

Example Purpose

Description

13. Generator, Time
Mark

Variable marker frequency
from 10 ms to 10 ns; accura-

Tektronix TG 501ATime

Mark Generator

1

cy within 2 ppm

14. Probe, 10X, in-

cluded with this

A P6205 or P6139A probe

2

Tektronix part number P6205 or

P6139A

instrument

15. Generator,

Video Signal

16. Oscillator, Lev-

Provides PAL compatible
outputs

60 Hz. Sine Wave

Tektronix TSG 121 Used to Test Video

Tektronix part number SG 502
eled Sinewave
Generator

17. Pulse Generator Tektronix part number PG 502

18. Cable, Coaxial 75 O, 36 in, male to male BNC
connectors

19. Termination,

75 O

Impedance 75 O; connectors:

female BNC input, male BNC

Tektronix part number
012-1338-00

Tektronix part number
011-0102-01

output

Checking Sample-

Rate and Delay-time

Accuracy

Signal Interconnec-
tion

Option 05 Equipped

Instruments Only

Used to Test Video

Option 05 Equipped

Instruments Only

Used to Test Video

Option 05 Equipped

Instruments Only

Used to Test Video

Option 05 Equipped

Instruments Only

Used to Test Video

Option 05 Equipped

Instruments Only

1 Requires a TM 500 or TM 5000 Series Power Module Mainframe.

2 Warning: The P6205 probe provides an extremely low loading capacitance (<2 pF) to ensure the best possible signal reproduction.

This probe should not be used to measure signals exceeding ±10V, or errors in signal measurement will be observed. Above 40 V,
damage to the probe may result. To make measurements beyond ±10V, use either the P6139A probe (good to 500 V), or refer to
the catalog for a recommended probe.

TDS 620A, 640A, & 644A Service Manual 4-15

Performance Tests

4-16 Performance Verification

Performance Tests

Test Record

Photocopy the next four pages and use them to record the performance test
results for your instrument.

TDS 620A, 640A, & 644A Test Record

Instrument Serial Number

Temperature

1

nate of Calibration

Performance Test

CH1 Offset +1 mV

+ 100 mV
+1 V

CH2 Offset +1 mV

+ 100 mV
+1 V

CH3 Offset +1 mV

+ 100 mV
+1 V

CH4 Offset +1 mV

+ 100 mV
+1 V

1

Certificate Number
RH

Technician1

Minimum Incoming Outgoing Maximum

Offset Accuracy

- 1.45 mV

- 68.5 mV

- 685 mV

- 1.45 mV

- 68.5 mV

- 685 mV

- 1.45 mV

- 68.5 mV

- 685 mV

- 1.45 mV

- 68.5 mV

- 685 mV

DC Voltage Measurement Accuracy (Averaged)

+ 1.45 mV
+ 68.5 mV
+ 685 mV

+ 1.45 mV
+ 68.5 mV
+ 685 mV

+ 1.45 mV
+ 68.5 mV
+ 685 mV

+ 1.45 mV
+ 68.5 mV
+ 685 mV

CH1

5 mV Vert scale setting,

-5 niv position setting

CH1

5 mV Vert scale setting,

+5 niv position setting

CH1

200 mV Vert scale setting,

-5 niv position setting

CH1

200 mV Vert scale setting,

+5 niv position setting

CH1 1 V Vert scale setting,

-5 niv position setting

CH1 1 V Vert scale setting,

+5 niv position setting

CH2

5 mV Vert scale setting,

-5 niv position setting

CH2

5 mV Vert scale setting,

+5 niv position setting

+ 1.0329 V + 1.0471 V

- 1.0471 V - 1.0329 V

+ 11.405 V + 11.795 V

- 11.795 V - 11.405 V

+ 98.81 V + 101.19 V

- 101.19 V

- 98.81 V

+ 1.0329 V + 1.0471 V

- 1.0471 V - 1.0329 V

TDS 620A, 640A, & 644A Service Manual

4-17

Performance Tests

TDS 620A, 640A, & 644A Test Record (Cont.)

Instrument Serial Number Certificate Numher:

Temperature: RH

nate nf Calihratinn:

Technician:

Performance Test

CH2

200 mV Vert scale setting,

-5 niv pnsitinn setting

CH2

200 mV Vert scale setting,

+5 niv pnsitinn setting

CH2 1 V Vert scale setting,

-5 niv pnsitinn setting

CH2 1 V Vert scale setting,

+5 niv pnsitinn setting

CH3 5 mV Vert scale setting,

-5 niv pnsitinn setting

CH3 5 mV Vert scale setting,

+5 niv pnsitinn setting

CH3 200 mV Vert scale setting,

-5 niv pnsitinn setting

CH3 200 mV Vert scale setting,

+5 niv pnsitinn setting

CH3

1 V Vert scale setting,

-5 niv pnsitinn setting

Minimum Incoming Outgoing Maximum

+ 11.405 V + 11.795 V

- 11.795 V - 11.405 V

+ 98.81 V + 101.19 V

- 101.19 V

- 98.81 V

+ 1.0329 V + 1.0471 V

- 1.0471 V - 1.0329 V

+ 11.405 V + 11.795 V

- 11.795 V - 11.405 V

+ 98.81 V + 101.19 V

CH3

1 V Vert scale setting,

- 101.19 V

- 98.81 V

+5 niv pnsitinn setting

CH4

5 mV Vert scale setting,

+ 1.0329 V + 1.0471 V

-5 niv pnsitinn setting

CH4

5 mV Vert scale setting,

- 1.0471 V - 1.0329 V

+5 niv pnsitinn setting

CH4

200 mV Vert scale setting,

+ 11.405 V + 11.795 V

-5 niv pnsitinn setting

CH4

200 mV Vert scale setting,

- 11.795 V - 11.405 V

+5 niv pnsitinn setting

CH4 1 V Vert scale setting,

+ 98.81 V + 101.19 V

-5 niv pnsitinn setting

CH4 1 V Vert scale setting,

- 101.19 V

- 98.81 V

+5 niv pnsitinn setting

4-18 Performance Verification

TDS 620A, 640A, & 644A Test Record (Cont.)

Performance Tests

Instrument Serial Numher

Certificate Numher

Temperatur RH

nate nf Calihratinn

Performance Test

Minimum Incoming Outgoing Maximum

Technician1

Analog Bandwidth

CH1 100 mV 424 mV N/A

CH2 100 mV 424 mV N/A

CH3 100 mV

424 mV N/A

CH4 100 mV 424 mV N/A

Delay Between Channels

nelay Between Channels

N/A

250 ps

Time Base System

Lnng Term Sample Rate/
nelay Time @ 500 ns/10 ms -4.0 niv +4.0 niv

nelta Time @ 5 ns (100 MHz) 19.760 ns

20.240 ns

Trigger System Accuracy

Pulse-Glitch nr Pulse-WIdth,
Hnr. scale < 1 ms

Lnwer Limit
Upper Limit

2.5 ns

2.5 ns

7.5 ns

7.5 ns
Pulse-Glitch nr Pulse-WIdth,
Hnr. scale > 1 ms

Lnwer Limit
Upper Limit

Main Trigger, nC Cnupled)

Main Trigger, nC Cnupled)
nelayed Trigger, nC Cnupled)

nelayed Trigger, nC Cnupled)

1 MS
1 ms

9.863 V

9.863 V

3 Ms
3 Ms

10.137 V

10.137 V

Output Signal Checks

MAIN TRIGGER OUTPUT, 1 M O High > 2.5 V Lnw < 0.7 V

MAIN TRIGGER OUTPUT, 50 O High > 1.0 V Lnw < 0.25 V

nELAYEn TRIGGER OUTPUT, 50 O High > 1.0 V Lnw < 0.25 V

nELAYEn TRIGGER OUTPUT, 1 M O High > 2.5 V Lnw < 0.7 V

CH 3 SIGNAL OUTPUT, 1 M O Pk-Pk > 80 mV Pk-Pk < 120 mV

CH 3 SIGNAL OUTPUT, 50 O Pk-Pk > 40 mV Pk-Pk < 60 mV

TDS 620A, 640A, & 644A Service Manual 4-19

Performance Tests

TDS 620A, 640A, & 644A Test Record (Cont.)

Instrument Serial Number:

Temperature: RH

nate nf Calibration Technician:

Performance Test

Frequency (CH1 Freq.) 950 Hz 1050 Hz

Vnltage (difference) 495 mV

Minimum Incoming Outgoing Maximum

Probe Compensator Output Signal

Certificate Number

505 mV

4-20 Performance Verification

Performance Tests

Signal Acquisition These procedures check those characteristics that relate to the signal-acqui-
Svstem Checks sition system and are listed as checked under Warranted Characteristics in

v

Section 1, Specifications.

Check Accuracv of Offset (Zero Setting)

Equipment Required: None.

Prerequisites: The oscilloscope must meet the prerequisites listed on

page 4-13.

1. Preset the instrument controls:

a. Initialize the oscilloscope:

• Press save/recall SETUP

• Press the main-menu button Recall Factorv Setup.

• Press the side-menu button OK Confirm Factorv Init.

• Press CLEAR MENU to remove the menus from the screen.

b. Modify the default settings:

• Set the horizontal SCALE to 1 ms.

• Press SHIFT; then press ACQUIRE MENU.

• Press the main-menu button Mode; then press the side-menu
button Average 16.

• Press DISPLAY.

• Press the main-menu button Graticule; then press the side-
menu button Frame.

• Press CURSOR.

• Press the main-menu button Function; then press the side-
menu button H Bars.

• Press CLEAR MENU.

• Be sure to disconnect any input signals from all four channels.

2. Confirm input channels are within limits for offset accuracy at zero offset:
Do the following substeps — test CH 1 first, skipping substep a since

CH 1 is already set up to be checked from step 1.

a. Select an unchecked channel: Press WAVEFORM OFF to remove

the channel just confirmed from the display. Then, press the front-

panel button that corresponds to the channel you are to confirm.

TDS 620A, 640A, & 644A Service Manual

4-21

Performance Tests

Table 4-2: DC Offset Accuracy (Zero Setting)

Vertical Scale Setting Vertical Position and Offset Accuracy

Offset Setting

1 mV

0 ±1.45 mV

1

Limits

100 mV 0 ±68.5 mV

1 V

1 Vertical position is set to 0 divisions and vertical offset to 0 V when the oscilloscope is

initialized in step 1.

0 ±685 mV

b. Set the vertical scale: Set the vertical SCALE to one of the settings

listed in Table 4-2 that is not yet checked. (Start with the first setting
listed.)

c. Display the test signal: The baseline DC test level was initialized for

all channels in step 1 and is displayed as you select each channel
and its vertical scale. Be sure not to use the vertical POSITION knob
while checking any channel for accuracy of offset, since varying the

position invalidates the check.

d. Measure the test signal: Rotate the general purpose knob to super-

impose the active cursor over the baseline DC test level. (Ignore the

other cursor.)

e. Read the measurement results at the absolute (@:) cursor readout,

not the delta (A:) readout on screen (see Figure 4-4).

f. Check against limits: Do the following subparts in the order listed.

• CHECK that the measurement results are within the limits listed
for the current vertical scale setting.

• Repeat substeps b through f until all vertical scale settings listed

in Table 4-2, are checked for the channel under test.

4-22

Performance Verification

Ignore the

inactive cursor.

Align the active

cursor to the DC

baseline (no input).

Then read the

offset relative to

ground reference.

Run: SO.OkS/s Average

ami

Performance Tests

vn.OOms Ch1 1 .OOmv

O

V 9 Feb 1993

12:30:28

cz>

a a a a

Figure 4-4: Measurement of DC Offset Accuracy at Zero Setting

g. Test all channels: Repeat substeps a through f for all input channels.

3. Disconnect the hookup: No hookup was required.

Check DC Gain and Voltage Measurement Accuracy

Performance of this procedure requires input voltages up to

92 VDC. Be sure to set the DC calibration generator to 0 volts

before connecting, disconnecting, and/or moving the test hookup

during the performance of this procedure.

Equipment Required: Two dual-banana connectors (Item 6), one BNC T

connector (Item 7), one DC calibration generator (Item 9), and two precision
coaxial cables (Item 5).

Prerequisites: The oscilloscope must meet the prerequisites listed on
page 4-13.

Procedure:

1. Install the test hookup and preset the instrument controls:

a. Hook up the test-signal source:

• Set the output of a DC calibration generator to 0 volts.

TDS 620A, 640A, & 644A Service Manual 4-23

Performance Tests

Connect the output of a DC calibration generator through a
dual-banana connector followed by a 50 O precision coaxial
cable to one side of a BNC T connector. See Figure 4-5.

Connect the Sense output of the generator through a second
dual-banana connector followed by a 50 O precision coaxial
cable to the other side of the BNC T connector. Now connect the
BNC T connector to CH1. See Figure 4-5.

Dual Banana to

BNC Adapters

DC Calibrator

ill

II

^ aooaoaa

, I

500 Coaxial Cables

Figure 4-5: Initial Test Hookup

b. Initialize the oscilloscope:

Press save/recall SETUP!

Press the main-menu button Recall Factory Setup.

Press the side-menu button OK Confirm Factory Init.

Modify the default settings:

Press SHIFT; then press ACQUIRE MENU.

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0

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0

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<=> C=> CD

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BNC T

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4-24

Press the main-menu button Mode; then press the side-menu
button Average 16.

Press CURSOR.

Press the main-menu button Function; then press the side-
menu button H Bars.

Press DISPLAY.

Press the main-menu button Graticule; then press the side-
menu button Frame.

2. Confirm input channels are within limits for DC delta voltage accuracy:
Do the following substeps — test CH 1 first, skipping substep 2a since

CH 1 is already selected from step 1.

a. Select an unchecked channel:

• Set the generator output to 0 V.

Performance Verification

Performance Tests

• Press WAVEFORM OFF to remove the channel just confirmed

from the display.

• Press the front-panel button that corresponds to the next chan-
nel you are to confirm.

• Move the test hook up to the channel you select.

b. Display the test signal:

• Press VERTICAL MENU. Press the main-menu button Position.

• Use the keypad to set vertical position to -2.5 divisions (press

-2.5, then ENTER, on the keypad).

c. Measure the test signal:

• Press CLEAR MENU. Use the general purpose knob to precise-
ly align the active cursor to the DC baseline level on screen.

• Set the generator output to 500 mV.

• Press SELECT. Use the general purpose knob to precisely align

the alternate cursor to the 500 mV DC test level on screen.

First align a cursor to the

DC baseline (no input).

Second align the second

cursor to the DC test level

that you input.

Third read the results

of the ADC

measurement here.

• Press CLEAR MENU. Read the measurement results from the
delta (A:) readout, not the absolute (@:) readout. See Fig-
ure 4-6.

Run: 100kS/s

Ol
0

0
0
OJ

BIB ToÖmV

a

M 500(JS Chi I 0V 9 Feb 1993

a

14:14:

a.

Figure 4-6: Measurement of the DC Accuracy for Delta Measurements

d. Check against limits: CHECK that the A: readout on screen is within

482 mV to 518 mV.

TDS 620A, 640A, & 644A Service Manual 4-25

Performance Tests

e. Test all channels: Repeat substeps a through d for all four channels.

Reestablish the initial test hookup setup:

3

a. Hook up the test-signal source:

• Set the output of the DC calibration generator to 0 volts.

• Move the BNC T connector back to CH 1.

b. Initialize the oscilloscope:

• Press save/recall SETUP!

• Press the main-menu button Recall Factory Setup.

• Press the side-menu button OK Confirm Factory Init.

c. Modify the default settings:

• Press SHIFT; then press ACQUIRE MENU.

• Press the main-menu button Mode; then press the side-menu
button Average 16.

• Press DISPLAY.

• Press the main-menu button Graticule; then press the side-
menu button Frame.

4,

Confirm input channels are within limits for DC accuracy at maximum

offset and position: Do the following substeps — test CH 1 first, skipping

substep 4a since CH 1 is already selected from step 3.

a. Select an unchecked channel:

• Press WAVEFORM OFF to remove the channel just confirmed

from the display.

• Press the front-panel button that corresponds to the channel

you are to confirm.

• Set the generator output to OV.

• Move the test hookup to the channel you selected.

b. Turn on the measurement Mean for the channel:

• Press MEASURE, then press the main-menu button Select

Measrmnt for CHx.

• Press the side-menu button more until the menu label Mean

appears in the side menu (its icon is shown at the left). Press the
side-menu button Mean.

• Press CLEAR MENU.

c. Set the vertical scale: Set the vertical SCALE to one of the settings

listed in Table 4-3 that is not yet checked. (Start with the first setting
listed.)

4-26 Performance Verification

Table 4-3: DC Accuracy

Performance Tests

Scale
Setting

Position
Setting
(Divs)

5 mV -5

+5

200 mV -5

+5

1 V

-5

+5

d. Display the test signal:

• Press VERTICAL MENU. Press the main-menu button Position.

• Use the keypad to set vertical position to -5 divisions (press

-5, then ENTER, on the keypad). The baseline level will move

offscreen.

• Press the main-menu button Offset.

• Use the keypad to set vertical offset to the positive-polarity

setting listed in the table for the current vertical scale setting.
The baseline level will remain off screen.

Offset

Setting

+ 1 V

Generator
Setting

+ 1.040 V + 1.0329 V to +1.0471 V

-1 V -1.040 V

+ 10 V + 11.6 V

-10 V -11.6 V

+92 V + 100 V

-92 V -100 V

Accuracy

Limits

-1.0329 V to -1.0471 V

+ 11.405 V to +11.795 V

-11.405 V to -11.795 V

+98.81 V to +101.19 V

-98.81 V to -101.19 V

• Set the generator to the level and polarity indicated in the table

for the vertical scale, position, and offset settings you have

made. The DC test level should appear on screen. (If it doesn't
return, the DC accuracy check is failed for the current vertical

scale setting of the current channel.)

e. Measure the test signal: Press CLEAR MENU. Read the measure-

ment results at the Mean measurement readout. See Figure 4-7.

TDS 620A, 640A, & 644A Service Manual

4-27

Performance Tests

First set vertical position and offsets
to maximum (no input). Note gnd ref
indicator bounded on-screen for the

offset baseline below screen.

Second, input a DC

level equal to the offset

plus 3 divisions.

Third, turn on the

Measurement called

mean and read the

results here.

Figure 4-7: Measurement of DC Accuracy at Maximum Offset and Position

f. Check against limits:

• CHECK that the readout for the measurement Mean readout on

screen is within the limits listed for the current vertical scale and

position/offset/generator settings.

• Repeat substep d, reversing the polarity of the position, offset,
and generator settings as is listed in the table.

• CHECK that the Mean measurement readout on screen is within
the limits listed for the current vertical scale setting and position/

offset/generator settings.

• Repeat substeps c through f until all vertical scale settings, listed

in Table 4-3, are checked for the channel under test.

g. Test all channels: Repeat substeps a through f for all four channels.

5. Disconnect the hookup:

a. Set the generator output to OV.

b. Disconnect the cable from the generator output at the input connec-

tor of the channel last tested.

4-28 Performance Verification