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