Tektronix WFM90, WFM91 User Manual

Service Manual

WFM 90 and WFM 91
Handheld Waveform, Vector, Picture,
and Audio Monitor

070-8969-04

This document supports firmware version 1.00
and above.

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 © T ektronix, Inc. All rights reserved.
T ektronix 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.
T ektronix, Inc., P.O. Box 1000, Wilsonville, OR 97070–1000
TEKTRONIX and TEK are registered trademarks of T ektronix, Inc.

WARRANTY

T ektronix warrants that the products that it manufactures and sells will be free from defects in materials and workmanship
for a period of one (1) year from the date of shipment. If a product proves defective during this warranty period, T ektronix,
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 T ektronix, with shipping charges prepaid.
T ektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the
T ektronix 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. T ektronix shall not be obligated to furnish service under this warranty a) to repair damage resulting
from attempts by personnel other than T ektronix 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-T ektronix 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 P ARTICULAR PURPOSE. TEKTRONIX’ RESPONSIBILITY TO
REP AIR 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.

Service Assurance

If you have not already purchased Service Assurance for this product, you may do so at any time during the product’s
warranty period. Service Assurance provides Repair Protection and Calibration Services to meet your needs.

Repair Protection extends priority repair services beyond the product’s warranty period; you may purchase up to three
years of Repair Protection.

Calibration Services provide annual calibration of your product, standards compliance and required audit documentation,
recall assurance, and reminder notification of scheduled calibration. Coverage begins upon registration; you may purchase
up to five years of Calibration Services.

Service Assurance Advantages

H Priced well below the cost of a single repair or calibration
H A void delays for service by eliminating the need for separate purchase authorizations from your company
H Eliminates unexpected service expenses

For Information and Ordering

For more information or to order Service Assurance, contact your T ektronix representative and provide the information
below . Service Assurance may not be available in locations outside the United States of America.

Name VISA or Master Card number and expiration
Company date or purchase order number
Address Repair Protection (1,2, or 3 years)
City , State, Postal code Calibration Services (1,2,3,4, or 5 years)
Country Instrument model and serial number
Phone Instrument purchase date

Table of Contents

Specifications

Operating Information

Theory of Operation

General Safety Summary vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Service Safety Summary xi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Preface xiii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction xv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Service Strategy xv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Service Offerings xv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Before You Begin xvii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Product Description 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Characteristics T ables 1–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Installation 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating Information 2–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Block Diagram Description 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Performance Verification

Summary Verification 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Equipment Required 4–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Performance Verification Procedures 4–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Adjustment Procedures

Summary Adjustment 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Equipment Required 5–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Adjustment Procedures 5–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Maintenance

Preparation 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Inspection and Cleaning 6–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

After Repair Adjustments 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Repackaging Instructions 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Removal and Replacement 6–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T ools Required 6–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures 6–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Troubleshooting Procedures 6–31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Equipment Required 6–31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Battery-Fault Analysis 6–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Low-Voltage Power Supply 6–35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

WFM 90 and WFM 91 Service Manual

i

Table of Contents

Options

Replaceable Parts List

Diagrams

Fault Symptom T able 6–35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Troubleshooting Flowcharts 6–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Connector Diagram 6–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Options 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Accessories 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Parts Ordering Information 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Using the Replaceable Parts List 8–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Diagrams 9–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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WFM 90 and WFM 91 Service Manual

List of Figures

Table of Contents

Figure 2–1: Installing the viewing hood 2–2. . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–2: Installing the desk stand 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–3: Instrument front panel 2–4. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–4: Instrument side panels 2–7. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–5: On-screen readout messages 2–9. . . . . . . . . . . . . . . . . . . . . . .

Figure 3–1: Simplified block diagram 3–3. . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 4–1: –3 dB marks on the vector graticule 4–12. . . . . . . . . . . . . . . . .

Figure 5–1: NTSC graticule showing the vector gain adjustment 5–9. . .

Figure 6–1: Removing the top cover 6–7. . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 6–2: Installing the LCD display cable 6–9. . . . . . . . . . . . . . . . . . . .

Figure 6–3: Installing the LCD display 6–11. . . . . . . . . . . . . . . . . . . . . . . . .

Figure 6–4: Installing the keypad 6–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 6–5: Installing the Top board shield 6–15. . . . . . . . . . . . . . . . . . . . .

Figure 6–6: Installing the Bottom board 6–17. . . . . . . . . . . . . . . . . . . . . . . .

Figure 6–7: Installing the battery cover 6–19. . . . . . . . . . . . . . . . . . . . . . . .

Figure 6–8: Removal and replacement of the turnlock stud 6–20. . . . . . . .

Figure 6–9: Removing the NiCad battery pack 6–22. . . . . . . . . . . . . . . . . .

Figure 6–10: Installed polarity of alkaline batteries 6–23. . . . . . . . . . . . . .

Figure 6–11: Battery contact installation alignment 6–25. . . . . . . . . . . . . .

Figure 6–12: Battery power-wire and turnlock stud receptacle

installation 6–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 6–13: Battery orientation marker position 6–28. . . . . . . . . . . . . . . .

Figure 6–14: Installing the EMI suppressor 6–29. . . . . . . . . . . . . . . . . . . . .

Figure 6–15: Testing the battery charging circuit – WFM 90 SN B011362

and below; WFM 91 SN B010470 and below 6–32. . . . . . . . . . . . . . . . .

Figure 6–16: Testing the battery charging circuit – WFM 90 SN B011363

and above; WFM 91 SN B010471 and above 6–33. . . . . . . . . . . . . . . . .

Figure 6–17: Flowchart for no display 6–37. . . . . . . . . . . . . . . . . . . . . . . . .

Figure 6–18: Flowchart for distorted waveform display 6–38. . . . . . . . . . .

Figure 6–19: Flowchart for no vector display 6–39. . . . . . . . . . . . . . . . . . . .

Figure 6–20: Flowchart for bad audio display 6–40. . . . . . . . . . . . . . . . . . .

Figure 6–21: Flowchart for no picture display 6–41. . . . . . . . . . . . . . . . . . .

Figure 6–22: Flowchart for bad graticules and menus 6–42. . . . . . . . . . . .

WFM 90 and WFM 91 Service Manual

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Table of Contents

Figure 6–23: Flowchart for all white display 6–43. . . . . . . . . . . . . . . . . . . .

Figure 6–24: Flowchart for untriggered waveform display 6–44. . . . . . . .

Figure 6–25: Flowchart for unlocked vector display 6–45. . . . . . . . . . . . . .

Figure 6–26: Flowchart for vector display jitter 6–46. . . . . . . . . . . . . . . . .

Figure 6–27: Flowchart for distorted vectors 6–46. . . . . . . . . . . . . . . . . . . .

Figure 6–28: Flowchart for problems with the instrument controls 6–47.

Figure 6–29: Flowchart for bad menus in the picture display 6–48. . . . . .

Figure 6–30: Flowchart for dim or blotchy display 6–49. . . . . . . . . . . . . . .

Figure 6–31: Flowchart for bad displays except Picture mode 6–49. . . . . .

Figure 6–32: Circuit board connector and pin locations 6–50. . . . . . . . . . .

Figure 8–1: Exploded view 8–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 9–1: Interconnect diagram 9–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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WFM 90 and WFM 91 Service Manual

List of Tables

Table of Contents

Table 1–1: Vertical deflection system 1–6. . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–2: DC restoration 1–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–3: Audio mode 1–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–4: Horizontal deflection system 1–8. . . . . . . . . . . . . . . . . . . . . . . .

Table 1–5: Vector mode 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–6: Synchronization 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–7: Physical characteristics 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–8: Environmental characteristics 1–10. . . . . . . . . . . . . . . . . . . . . .

Table 1–9: Power source 1–11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–10: Safety/EMI 1–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 2–1: Front panel and menu default settings 2–10. . . . . . . . . . . . . . .

Table 4–1: Summary verification procedure 4–1. . . . . . . . . . . . . . . . . . . .

Table 4–2: Equipment required for performance verification 4–2. . . . . .

Table 5–1: Summary adjustment 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 5–2: Equipment required for performance verification 5–2. . . . . .

Table 6–1: Tools required for module removal 6–5. . . . . . . . . . . . . . . . . .

Table 6–2: Removal and replacement procedure list 6–6. . . . . . . . . . . . .

Table 6–3: Equipment required for troubleshooting 6–31. . . . . . . . . . . . .

Table 6–4: Low-voltage power supplies 6–35. . . . . . . . . . . . . . . . . . . . . . . .

Table 6–5: Fault symptom table 6–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 8–1: Replaceable parts list column descriptions 8–2. . . . . . . . . . . .

WFM 90 and WFM 91 Service Manual

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Table of Contents

vi

WFM 90 and WFM 91 Service Manual

General Safety Summary

Review the following safety precautions to avoid injury and prevent damage to
this product or any products connected to it.

Only qualified personnel should perform service procedures.

To avoid potential hazards, use this product only as specified.

To Avoid Fire or Shock Hazards:

Use Proper Power Source. Do not operate this product from a power source that

applies more than the voltage specified.

Use Proper AC Adapter. Use only the specified ac adapter provided with this
product to connect it to the mains supply.

Avoid Electric Overload. To avoid electric shock or fire hazard, do not apply a
voltage to a terminal that is outside the range specified for that terminal.

Do Not Operate Without Covers. To avoid electric shock or fire hazard, do not
operate this product with covers or panels removed.

Use Proper Fuse. To avoid fire hazard, use only the fuse type and rating specified
for this product.

Do Not Operate in Wet/Damp Conditions. To avoid electric shock, do not operate
this product in wet or damp conditions.

Do Not Operate in an Explosive Atmosphere. To avoid injury or fire hazard, do not
operate this product in an explosive atmosphere.

Do Not Operate With Suspected Failures. If you suspect there is damage to this
product, have it inspected by qualified service personnel.

Observe All Ratings. Observe and follow all ratings and markings on the product.
Consult the product manual(s) for further ratings information before making any
connections to the product.

This product is intended to be connected to electrical devices with their common
at ground potential. Do not connect to elevated or floating common voltages.

WFM 90 & WFM 91 Service Manual

vii

General Safety Summary

Observe These Battery

Precautions

Battery Recycling

For information on replacing and recharging batteries specific to this product,
refer to the detailed instructions provided in this manual.

Replace Batteries Properly . Before replacing batteries, turn the instrument off
and disconnect the AC adapter.

Use only the size and type of batteries specified for this product. Be sure to
install the batteries in the proper polarity. Use care not to short battery terminals
together when replacing batteries.

When replacing alkaline batteries, all batteries should be replaced at the same
time.

Recharge Batteries Properly. Do not attempt to recharge alkaline batteries.
NiCad batteries are automatically recharged in this instrument.
Replace the NiCad battery pack if the batteries do not recharge within the

recommended time, or if the operating time from a full charge seems significant­ly shortened.

This product contains a Nickel Cadmium (NiCd) battery, which must be recycled
or disposed of properly. For the location of a local battery recycler in the U.S. or
Canada, please contact:

RBRC (800) BATTERY
Rechargeable Battery Recycling Corp. [phone]
P.O. Box 141870 www.rbrc.com
Gainesville, Florida 32614

viii

WFM 90 & WFM 91 Service Manual

General Safety Summary

Symbols and Terms

T erms in this Manual. These terms may appear in this manual:

WARNING. Warning statements identify conditions or practices that could result
in injury or loss of life.

CAUTION. Caution statements identify conditions or practices that could result in
damage to this product or other property.

T erms on the Product. These terms may appear on the product:
DANGER indicates an injury hazard immediately accessible as you read the

marking.
WARNING indicates an injury hazard not immediately accessible as you read the

marking.
CAUTION indicates a hazard to property including the product.

Symbols on the Product. The following symbols may appear on the product:

Certifications and

Compliances

DANGER

High Voltage

Protective Ground

(Earth) T erminal

ATTENTION

Refer to Manual

Double

Insulated

Refer to the specifications section for a listing of certifications and compliances
that apply to this product.

WFM 90 & WFM 91 Service Manual

ix

General Safety Summary

x

WFM 90 & WFM 91 Service Manual

Service Safety Summary

Only qualified personnel should perform service procedures. Read this Service
Safety Summary and the General Safety Summary before performing any service

procedures.
Do Not Service Alone. Do not perform internal service or adjustments of this

product unless another person capable of rendering first aid and resuscitation is
present.

Disconnect Power. To avoid electric shock, disconnect the power by means of
the ac adapter or, if provided, the power switch.

Use Care When Servicing With Power On. Dangerous voltages or currents may
exist in this product. Disconnect power, remove battery (if applicable), and
disconnect test leads before removing protective panels, soldering, or replacing
components.

To avoid electric shock, do not touch exposed connections.

WFM 90 & WFM 91 Service Manual

xi

Service Safety Summary

xii

WFM 90 & WFM 91 Service Manual

Preface

About This Manual

This manual provides instructions for servicing the WFM 90 and WFM 91
Handheld Waveform, Vector, Picture, and Audio Monitors. This manual
describes features and specifications that are common to all generator modules.
These include system configuration and the common control interface.

This manual is composed of the following sections:
H Specifications lists the electrical and environmental specifications and

provides a general product description.
H Operating Information describes installation and front panel operation of the

instrument.
H Theory of Operation contains a module-level description based on block

diagrams of the instrument circuitry.
H Performance Verification provides procedures for verifying instrument

performance.

Related Manuals

H Adjustment Procedures provides procedures for adjusting the instrument to

meet performance levels listed in Specifications.
H Maintenance contains instructions for cleaning the instrument, procedures

for removal and replacement of instrument modules, and troubleshooting

procedures.

H Options lists all of the options that you might find on your instrument.
H Replaceable Electrical Parts points you to Replaceable Mechanical Parts

for the list of replaceable electrical parts and assemblies.

H Diagrams contains the instrument interconnect diagram.
H Replaceable Mechanical Parts lists the part numbers of the replaceable

electrical and mechanical parts and assemblies.

The WFM 90 and WFM 91 Handheld Waveform, Vector, Picture, and Audio
Monitor User Manual (Tektronix part number 070-8968-XX) describes in detail
how to operate the instrument.

WFM 90 and WFM 91 Service Manual

xiii

Preface

xiv

WFM 90 and WFM 91 Service Manual

Introduction

Service Strategy

NOTE. Throughout this manual, any field-replaceable component, assembly, or
part of this oscilloscope is referred to generically as a module.

This manual contains all the information needed for periodic maintenance of the
WFM90 or WFM91 Handheld Waveform, Vector, Picture, and Audio Monitor.
(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. The procedures, diagrams, and other troubleshooting
aids help isolate failures to a specific module, rather than to components of that
module. Once a failure is isolated, replace the module with a unit obtained from
Tektronix, Inc.

All modules are listed in Mechanical Parts List. To isolate a failure to a module,
use the troubleshooting procedures located in Maintenance. To remove and
replace any failed module, follow the removal and replacement instructions
located in Maintenance.

Service Offerings

Warranty Repair 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 instrument. Tektronix technicians are apprised of the
latest information on improvements to the product as well as the latest new
options to the product.

Tektronix warrants this product for one year from date of purchase. (The
warranty appears after the title page and copyright page in this manual.)
Tektronix technicians provide warranty service at most Tektronix service
locations worldwide. Your Tektronix product catalog lists all service locations
worldwide.

WFM 90 and WFM 91 Service Manual

xv

Introduction

Repair or Calibration

Service

The following services may be purchased to tailor repair and/or calibration of
your WFM90 or WFM91 Handheld Waveform, Vector, Picture, and Audio
Monitor to fit your requirements:

Option M2. When you order option M2, you receive a five year warranty and
remedial service agreement.

Option M8. When you order option M8, you receive four free calibration and
performance tests.

At-Depot Service. Tektronix offers several standard-priced adjustment (calibra­tion) and repair services:

H A single repair and/or adjustment.
H Calibrations using equipment and procedures that meet the traceability

standards specific to the local area.

H Annual maintenance agreements that provide for either calibration and repair

or calibration only of the instrument.

Of these services, the annual maintenance agreement offers a particularly
cost-effective approach to service for many owners of the WFM90 or WFM91
Handheld Waveform, Vector, Picture, and Audio Monitor. Such agreements can
be purchased to span several years.

Self Service

On-Site Service. The annual maintenance agreement can be purchased with

on-site service, with repair and calibration done at your facility. This service
reduces the time your instrument is out of service when calibration or repair is
required.

Service Training. Tektronix provides service training in a number of programs. In
addition to classes held at our Beaverton campus, special classes at convenient
locations can be arranged.

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 allowing 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 has a 90-day service warranty.

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WFM 90 and WFM 91 Service Manual

Before You Begin

Introduction

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 has a 90-day
service warranty.

1-800-TEK-WIDE. For more information about any of the Tektronix service
offerings, US and Canadian customers can call our 24-hour service number at
1-800-TEK-WIDE. Service training questions may require specialists who are
only available between 8 am – 5 pm, Pacific time.

This manual is for servicing the WFM90 or WFM91 Handheld Waveform,
Vector, Picture, and Audio Monitor. To prevent injury to yourself or damage to
the instrument, do the following tasks before you attempt service:

H Be sure you are a qualified service person.
H Read the Safety Summary found at the beginning of this manual.
H Read Service Strategy in this section.

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

WFM 90 and WFM 91 Service Manual

xvii

Introduction

xviii

WFM 90 and WFM 91 Service Manual

Specifications

Specifications

Product Description

This section includes the following information:

H Product description
H Characteristics tables

Refer to Performance Requirements on page 1–5 for the conditions over which
the characteristics listed in this section are valid.

The Tektronix WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and
Audio Monitor is a self-contained, rasterizing television monitor. The instrument
has a built-in LCD color display device and is powered by batteries or by an AC
adapter producing 12 VDC.

This product can be used in traditional in-house applications of television
production, post-production, and signal transmission. The portability of this
instrument allows it to be used in untraditional applications, such as field
production and system maintenance.

Key Features

The following is a list of the key features of this instrument:
H Rasterized waveforms and graticules shown on the built-in color, four-inch

diagonal, TFT LCD display with viewing angle adjustment

H Powered by batteries or an AC adapter
H Menu-assisted monitoring operation
H Video and audio signal input and output capability
H Waveform, Vector, Picture, Audio, and Waveform-in-Picture (WIP) display

modes

H Line Select mode for the selection of any single line of video for display
H Time-out mode to shut off power to the display backlight and/or the

instrument when the instrument is not in use

H Signal level alarm mode for the waveform and audio displays
H Preset menu to store or recall the front panel and menu setup
H Instrument readjustment is performed entirely from the front panel

WFM 90 and WFM 91 Service Manual

1–1

Specifications

Description of Key

Features

The key features of this instrument are described below:

Rasterized Color LCD Display. This instrument uses a color, four-inch diagonal,
backlit, thin-film transistor (TFT) LCD raster display module. The proprietary
rasterizer displays analog waveforms or vectors simultaneously with the
appropriate measurement graticules. A viewing-angle control for the display
permits optimal signal viewing from different positions.

The LCD display retains an image if the instrument is left on in one display
mode for an extended period of time. This is typical for the LCD display device.
The retained image fades over time. The fading can be accelerated by leaving the
instrument turned off.

CAUTION. To prevent image retention in the LCD display, enable the backlight
time-out mode or turn the instrument off if the monitor will not be used for more
than two hours.

Battery or AC Adapter Operation. The instrument can be powered by six C-cell
batteries, alkaline or NiCad, or by an AC adapter wall unit with a negative center
lead producing 12 VDC. The rechargeable NiCad batteries are automatically
recharged when the 12 VDC adapter is plugged into the instrument (whether
instrument power is on or off). Alkaline batteries do not recharge. The message
Low Bat is displayed in the on-screen readout when the batteries get critically
low on power.

1–2

Menu-Assisted Monitoring Operation. The menus use a combination of on-screen

readout and multi-use buttons, in conjunction with the Arrow Buttons, to control
most of its monitoring functions. Enter the menus by pressing one of the Menu,
Config, or Line Sel buttons. Menus are exited by pressing the entry button for
the displayed menu, or by entering another menu.

Video and Audio Input/Output. The instrument displays signals from the one
channel of composite video input or from the one channel of audio input. An
external reference input allows the use of an external sync signal.

The video and external reference inputs each have a rear-panel switch providing
the choice of an internal 75 W signal termination or an unterminated high-imped­ance input. The audio input connector is a standard 3-pin XLR connector.

WFM 90 and WFM 91 Service Manual

Specifications

The video output will drive a remote monitor or video switcher. The audio signal
is output through a mini-headphone stereo jack that outputs the mono input
signal to both stereo channels. The audio volume is fixed for each reference
level. The larger the displayed signal, the louder the volume.

Waveform Display Mode. The Waveform display mode provides a voltage-versus­time display of the video signal with three standard sweep rates: 1H (5 ms/divi-
sion), 2H (10 ms/division), and 2F (two field). Each line-rate sweep can be
magnified X10 to the following sweep rates: 1H Mag (0.5 ms/division), and 2H
Mag (1 ms/division). The 2F sweep is magnified by approximately X20.

Vertical gain is fixed at X1 or X5, or is variable from 45% to 155% amplitude.
The gain setting tracks between the Waveform and Vector display modes. The
signal filters are Flat (no filter) and Luminance (low-pass filter). The Line Select
mode enables the selection of a single line of video for display.

Vector Display Mode. The Vector display mode presents an XY plot of the
demodulated chrominance phase and amplitude portion of the video signal. The
vector angle represents chrominance phase, and the distance from the center
represents chrominance amplitude. The vector display is useful when making
differential gain and phase measurements.

A full 360_ phase shifter and 75% and 100% color bar settings are provided.
Vector gain is fixed at X1 or X5, or is variable from 45% to 155% amplitude.
The gain setting tracks between the Waveform and Vector display modes. The
+V mode (PAL only) overlays the –V axis on the +V axis to check the PAL
system color encoders.

Picture Display Mode. The Picture display mode provides an unprocessed full
color display of the composite video signal. The NTSC Safe Action and Safe
Title areas, as well as the PAL Safe Area, can be highlighted. The vertical
interval portion of the signal can be viewed by vertically shifting the display.
Controls for adjusting the hue and color of the picture display are provided.

Audio Display Mode. The Audio display mode provides a voltage-versus-time
display of a single audio channel. The audio voltage is displayed on the vertical
scale with time on the horizontal scale at a two-field sweep rate.

Audio reference levels can be set to –10 dBu, 0 dBu, 4 dBu, or 8 dBu, with an
additional level available for microphone checks. The audio headroom reference
level can be set to –3 dB or +10 dB and is for audio signals below or above the
reference level, respectively.

WFM 90 and WFM 91 Service Manual

1–3

Specifications

Waveform-in-Picture Display Mode. The Waveform-in-Picture (WIP) display
mode provides a 1/4-screen-sized window over the Picture display for any one of
the Waveform, Vector, or Audio displays. The WIP window can be positioned to
any one of the four corners of the display. The Arrow Buttons retain their default
function for the display mode in the WIP window.

Line Select Mode. The Line Select mode enables you to select any line of video
for viewing in either the Waveform or Vector display modes. The desired line
can be selected from either all video fields or from alternating fields. With
two-field sweep selected in the Waveform display mode, the selected line is
highlighted in the field display.

Time-out Mode. When the Time-out mode is enabled, power is turned off to the
display backlight and/or the instrument when the front panel has not been in use
for a menu-selected length of time.

Amplitude Alarm Mode. The Amplitude Alarm mode provides automatic signal
level checking in the Waveform and Audio display modes. In the Waveform
display mode, the portion of the waveform exceeding the 100 IRE (1.0 V PAL)
graticule line is highlighted. In the Audio display mode, the portion of the
waveform exceeding the selected reference level is highlighted.

More Information

Preset Menu. The Preset menu allows you to store the current instrument front

panel and menu settings for future use. In addition, there is a menu selection that
sets the front-panel and menu settings back to the factory-set defaults. Refer to
Default Settings on page 2–10 for a list of the default settings.

Instrument Readjustment. This instrument can be adjusted entirely from the front
panel after entering the Calibration menu. Instructions for adjusting the
instrument are located in the Adjustment Procedures section of this manual.

The location of some additional information is listed below:
H Refer to Battery Operation on page 2–3 for information on operating the

instrument with batteries

H Front panel operation is described in the Operating Information section
H Instrument options are listed in the Options section
H Standard and optional accessories are listed in the Replaceable Mechanical

Parts section

1–4

WFM 90 and WFM 91 Service Manual

Characteristics Tables

Specifications

The characteristics tables use the following abbreviations:

Performance Requirement. All performance requirements in the characteristics
tables are identified with Req
in the Performance Verification section. Allow a warm-up time of 20 minutes
before performing the procedures.

Performance requirements in the electrical specifications are valid over an
ambient temperature range of +20° C to +30° C. The Performance Requirement
tolerances listed in the electrical specifications are doubled over the temperature
range of 0° C to +40° C, unless otherwise specified. Test equipment used to
verify performance requirements must be calibrated and working within the
limits specified in Equipment Required on page 4–2.

Reference Information. Information that amplifies a performance requirement or
is of special importance is indicated by REF. There is no need to check these
items to a specific tolerance.

and can be assured by performing the procedures

Safety Standards

The following safety standards apply to the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor:

ANSI/ISA S82. Safety Standard for Electrical and Electronic Test, Measuring,
Controlling, and Related Equipment.

CAN/CSA C22.2 No. 1010.1-92. Safety Requirements for Electrical Equipment for
Measurement, Control, and Laboratory Use.

IEC1010-1. Safety Requirements for Electrical Equipment for Measurement,
Control, and Laboratory Use (1990).

UL3111. Standard for Electrical Measuring and Test Equipment.

WFM 90 and WFM 91 Service Manual

1–5

Specifications

T able 1–1: Vertical deflection system

Category Description

Frequency Response REF: Specifications apply for full screen height video input signal with Vari-

able Gain off.

REQ: Flat Filter 1 V Full Scale: 50 kHz to 6 MHz within 2% of response at 50 kHz.
REQ: Flat Filter X5 Gain: 50 kHz to 6 MHz within 5% of response at 50 kHz.

REF: Low Pass Filter: w40 dB attenuation at 3.58 MHz (NTSC) or

4.43 MHz (PAL).

REF: Response at 15 kHz does not vary between Flat and Lum (low pass)

filters by more than 1%.

Deflection Factor REQ: 1 V Full Scale: 1 V input displayed within 1% of 140 IRE.

REF: Flat filter selected.

REQ: X5 Gain: Gain accuracy within 5% with 1 V input signal.

REF: X5 Gain Registration: v1 major division of vertical shift from baseline

between unmagnified and magnified signal.

REQ: Variable Gain Range: Input signals between 0.8 V and 2 V can be adjusted

to 140 IRE (1.0 V) display. 160 mV to 400 mV for X5 Gain.

REQ: Position Range: 1 V signal can be positioned so that peak white and sync tip

can be placed at blanking level with the DC Restorer on, regardless of gain
setting.

Transient Response REF: Specifications apply for full screen height video input signal with Vari-

able Gain off, 1 V Full Scale or X5 Gain selected, and Flat filter se­lected.

REF: Pulse-to-Bar Ratio:

X1: 0.99:1 to 1.01:1.
X5: 0.98:1 to 1.02:1.

REF: Preshoot: v1%.
REF: Overshoot:

X1: v2%.
X5: v4%.

REF: Ringing:

X1: v2%.
X5: v4%.

REF: Field Rate Tilt: v1%.
REF: Line Rate Tilt: v1%.

REQ: Overscan: v2% variation in baseline of 100 IRE (700 mV) 12.5T (20T)

modulated pulse as it is positioned over the middle 80% of the screen.

Maximum Absolute Input Level REF: $5 VDC plus peak AC.

REF: Displays in excess of 200 IRE (1.428 V) may cause frequency re-

sponse aberrations.

1–6

WFM 90 and WFM 91 Service Manual

T able 1–1: Vertical deflection system (Cont.)

Category Description

Specifications

DC Input Impedance
(Unterminated)

REQ: 15 kW.

REF: With input switch in the HIZ position.

Video Input Return Loss REF: 40 dB from 50 kHz to 6 MHz with 75 W termination on.
Video Out Return Loss (75W) REF: 30 dB from 50 kHz to 6 MHz.
Video Out Differential Gain (50% APL) REF: Within 1% with a 140 IRE (1.0 V PAL) unit display.
Video Out Differential Phase (50% APL) REF: Within 1° with a 140 IRE (1.0 V PAL) unit display.

T able 1–2: DC restoration

Category Description

DC Restorer Clamp Time REF: Back Porch.
Frequency Response at

60 Hz (50 Hz PAL)

REQ: Attenuation of 60 Hz (50 Hz PAL) on Input Signal:

Slow Mode: 20%.
Fast Mode: 90%.

REF: Blanking Level Shift with 10% to 90% APL Change:

APL changes from 50% to either 10% or 90% will cause blanking level
shift of 1 IRE unit (7.14 mV PAL) or less.

REF: Blanking Level Shift Due to Presence or Absence of Burst:

1 IRE unit (7.14 mV) or less shift from no color burst to presence of
color burst.

T able 1–3: Audio mode

Category Description

Reference Levels REQ: –10 dBu, 0 dBu, +4 dBu, +8 dBu.

REF: Nominal MIC Reference: –50 dBu.

Measurement Accuracy REQ: 0.5 dB at 1 kHz.
Frequency Response REQ: 0.5 dB from 50 Hz to 20 kHz.
Maximum Input Level Amplitude REF: +18 dBu.
DC Input Impedance REF: 15 kW.
Audio Output Connector REF: Mini stereo headphone jack.
Maximum Power Output REF: 250 mW.

WFM 90 and WFM 91 Service Manual

1–7

Specifications

T able 1–4: Horizontal deflection system

Category Description

Sweep REQ: Sweep will occur in all horizontal mode settings with or without synchroniza-

tion.

REF: Sweep Length: Two Line and Two Field sweep length is nominally

12 divisions.
1LINE Sweep Repetition Rate REQ: Equal to line rate of applied video or external sync.
2LINE Sweep Repetition Rate REQ: Equal to half line rate of applied video or external sync.
2FLD Sweep Repetition Rate REF: Displays 2 full fields, including the field-rate sync between them.
2FLD Sweep Magnification REF: Approximately X20.
Sweep Magnifier Registration REF: Magnification occurs about the center of the screen.
Timing Accuracy REF: All timing and linearity specifications exclude the first and last major

divisions of the unmagnified display.

REQ: 10 ms/division (2LINE): Within 2%.
REQ: 5 ms/division (1LINE): Within 2%.
REQ: 1 ms/division (2LINE + MAG): Within 2%.
REQ: 0.5 ms/division (1LINE + MAG): Within 3%.

Integral Linearity REQ: Within 1%.

REF: Measured between the 10 ms and 110 ms points on the 10 ms/division

(2LINE) sweep.
Horizontal Position REF: Any portion of a synchronized video sweep can be positioned on

screen in all sweep modes.

T able 1–5: Vector mode

Category Description

Chrominance Processing Nominal Subcarrier
Frequency (F

SC

)

Chrominance Processing Chrominance
Bandwidth

Chrominance Processing +V Mode
(Applicable to PAL operation only)

Display Vector Phase Accuracy REF: 1.25°.

Display Vector Gain Stability REF: Typically 2.5%.

REF: NTSC: 3.579545 MHz.

PAL: 4.43361875 MHz.

REQ: Upper –3 dB Point: F

+500 kHz, 100 kHz.

SC

Lower –3 dB Point: FSC – 500 kHz, 100 kHz.

REF: +V-type display as selected by front-panel button. When pushed, the

V axis is inverted at a 1/2 line rate to produce a single vector display.

REF: Measured with color bar signal.

Display Quadrature Phasing REF: Typically 0.5°.

1–8

WFM 90 and WFM 91 Service Manual

Specifications

T able 1–5: Vector mode (Cont.)

Category Description

Display Differential Phase REF: 1°.

REF: Measured with 140 IRE (1 V) linearity signal (5 step, 10 step, or Ramp)

with 40 IRE (300 mV) of subcarrier.

Display Differential Gain REF: 1%.

REF: Measured with 140 IRE (1 V) linearity signal (5 step, 10 step, or Ramp)

with 40 IRE (300 mV) of subcarrier.

Subcarrier Regenerator Pull-In Range REQ: NTSC: 50 Hz of FSC.

PAL: 10 Hz of F

REF: Subcarrier Regenerator free-runs in absence of appropriate signal.

Reference can be burst of either displayed signal or external reference
signal.

Subcarrier Regenerator Pull-In Time REF: Pull-In Time: Within 1 second, with subcarrier frequency within 50 Hz

(10 Hz for PAL) of FSC.

SC

.

Subcarrier Regenerator Phase Shift with
Subcarrier Frequency Change

Subcarrier Regenerator Phase Shift with Burst
Amplitude Change

Subcarrier Regenerator Phase Shift with Variable

REQ: NTSC: 2° from F

to (FSC + 50 Hz), or FSC to (FSC – 50 Hz).

SC

PAL: 2° from FSC to (FSC + 10 Hz), or FSC to (FSC – 10 Hz).

REQ: 2° from nominal burst amplitude to 6 dB.

REF: Internal or External burst reference.

REQ: 1° as gain is varied from +3 dB to –6 dB.

Gain Control
Subcarrier Regenerator Phase Control Range REF: 360° continuous rotation.
Subcarrier Regenerator Burst Jitter REF: 0.5° RMS or less.

REF: With 140 IRE (1 V) composite video input. INT or EXT referenced.

WFM 90 and WFM 91 Service Manual

1–9

Specifications

T able 1–6: Synchronization

Category Description

Input Requirements REQ: Internal Reference: Composite video or black burst with sync amplitudes

40 IRE (300 mV PAL) 6 dB.

REQ: External Reference: Sync amplitude between 143 mV and 4 V will synchro-

nize sweeps.

External Reference Input REQ: DC Input Impedance (unterminated): 15 kW.

REF: Return Loss (75 W): 40 dB from 50 kHz to 6 MHz (with 75 W ter-

mination on, instrument power on).

REF: Absolute Maximum Input Voltage: 12 VDC plus peak AC.

T able 1–7: Physical characteristics

Category Description

Dimensions REF: Instrument:

5 inches (127 mm).

3.15 inches (80.0 mm).

9.6 inches (243.8 mm).

Shipping Box:

13.25 inches x 13.75 inches x 6 inches inside
14 inches x 14.25 inches x 6.25 inches outside

Weight REF: With batteries and pouch:

3 lbs, 9 oz.

Without batteries and pouch:

1 lb, 14 oz.

Shipping weight with packaging:

5 lbs, 14 oz.

T able 1–8: Environmental characteristics

Category Description

Operating Altitude REQ: To 15,000 feet (4572 meters).

REF: IEC 1010-1 compliance to 2000 meters.

Operating Temperature REQ: 0° to +50° C.

REF: IEC 1010-1 compliance to +40° C.

Equipment Type REQ: Measurement.
Installation Category REQ: Installation Category I (as defined in IEC 1010-1, Annex J).

REF: Rated for indoor use only.

Pollution Degree REQ: Pollution Degree 2 (as defined in IEC 1010-1).

1–10

WFM 90 and WFM 91 Service Manual

Specifications

T able 1–8: Environmental characteristics (Cont.)

Category Description

Vibration — Operating REF: 15 minutes each axis at 0.015 inch, frequency varied from 10 Hz to

55 Hz to 10 Hz in 1-minute cycles with instrument secured to vibration
platform. Ten minutes each axis at any resonant point or at 55 Hz if no

resonant point is found.
Shock — Non-Operating REF: 100 g, 1/2 sine, 11 ms duration, 3 shocks per surface (18 total).
Transportation REF: Qualified under NTSC Test Procedure 1A, Category II (24-inch drop).
Humidity REF: Will operate at 95% relative humidity for up to five days. Meets the

five-day cycling humidity test as called out in Tektronix standard

062–2847–00.

T able 1–9: Power source

Category Description

Battery REF: 6 C-sized cell batteries, or Tektronix NiCad battery pack (Tektronix Part

Number. 146-0107-00).
Battery Charge Time REF: Fast Charge: 550 mA.

REF: Slow Charge: 150 mA.

Power Consumption REF: Picture Mode: 5.5 W

Waveform Mode: 7.2 W

Vector Mode: 7.2 W
Operating Time REF: Alkaline Batteries:

Picture Mode: 2.5 hours
Waveform Mode: 2 hours
Vector Mode: 2 hours

NiCad Batteries:

Picture Mode: 4 hours
Waveform Mode: 3 hours
Vector Mode: 3 hours

REF: Fully charged or new batteries.

External Power REQ: DC Source of 11 V to 18 V.

REF: Wall Unit Tektronix Part Numbers:

220 V European TUV 119–4540–00

240 V UK 119–4541–00

240 V Australia 119–4542–00

100 V Japan 119–4539–00

120 V North America 119–4538–00

WFM 90 and WFM 91 Service Manual

1–11

Specifications

T able 1–10: Safety/EMI

Category Description

Certifications REQ: Designed to meet or exceed:

ANSI/ISA S82 – Safety Standard for Electrical and Electronic Test, Measur­ing, Controlling, and Related Equipment.

CAN/CSA C22.2 No. 1010.1-92 – Safety Requirements for Electrical Equip­ment for Measurement, Control, and Laboratory Use.

IEC1010-1 – Safety Requirements for Electrical Equipment for Measure­ment, Control, and Laboratory Use (1990).

UL31 11 – Standard for Electrical Measuring and Test Equipment.

EMI Compliance REQ: Designed to meet or exceed:

U.S.: FCC 47 CFR Part 15, Subpart B, Class A.

EC Declaration of Conformity Meets intent of Directive 89/336/EEC for Electromagnetic Compatibility.

Compliance was demonstrated to the following specifications as listed in the
Official Journal of the European Communities:

EN 50081-1 Emissions:

EN 55022 Class B Radiated and Conducted Emissions

EN 50082-1 Immunity:

IEC 801-2 Electrostatic Discharge Immunity
IEC 801-3 RF Electromagnetic Field Immunity
IEC 801-4 Electrical Fast Transient/Burst Immunity

1–12

WFM 90 and WFM 91 Service Manual

Operating Information

Operating Information

This section contains the following information:

H Mechanical and electrical installation instructions
H Operating instructions that relate to the service of this instrument

Installation

Before installing the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture,
and Audio Monitor, refer to the Environmental Characteristic requirements,
located in Table 1–8 on page 1–10 of the Specifications section.

All qualification testing was performed with the factory shipped cabinet
installed. To guarantee compliance with specifications, only operate the
instrument in its cabinet.

Mechanical Installation

Follow these instructions when you are mechanically installing this instrument:

Unpacking. Save the shipping carton and packing materials (including antistatic
bag) in the event it becomes necessary to ship the instrument to a Tektronix
Service Center for service or repair. Refer to Repackaging Instructions on
page 6–4 for instructions on packaging the instrument for shipment.

Cabinet. The WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and
Audio Monitor is shipped installed in a cabinet. There are not any optional
cabinets available.

Viewing Hood. The optional viewing hood allows you to readily view the
instrument display in well-lighted situations. The hood is attached to the
instrument by first applying the supplied Velcro strips to the sides of the
instrument, and then pressing the flaps of the viewing hood onto the strips as
shown in Figure 2–1.

WFM 90 and WFM 91 Service Manual

2–1

Operating Information

Figure 2–1: Installing the viewing hood

Desk Stand. The optional desk stand provides the user with a stable means to

hold the instrument upright on a flat surface. The prongs of the stand are inserted
into the holes in the back of the instrument as illustrated in Figure 2–2.

2–2

Figure 2–2: Installing the desk stand

WFM 90 and WFM 91 Service Manual

Operating Information

Electrical Installation

Follow these instructions when physically installing this instrument:

Power Source. This instrument is designed to operate from either six C-cell
batteries, alkaline or rechargeable NiCad, or from an AC adapter wall unit
producing 12 VDC.

CAUTION. To avoid possible damage to the instrument circuitry when using a DC
power source other than the supplied AC adapter, ensure that the DC source is a
negative-ground +11 V to +18 V system with a negative center lead. The DC
source must provide 12 W of power.

Fuse. This instrument does not have an external power fuse. There are two fuses
located internally on the Bottom board. See page 6–34 of the Maintenance
section for instructions on how to check and replace the power supply fuses.

Battery Operation. The rechargeable NiCad batteries are automatically recharged
when the AC adapter is plugged into the instrument, whether the instrument
power is on or off. The battery charge time is approximately 6.5 hours when the
instrument is off and 20 hours when the instrument is on. The instrument shifts
into a safe trickle-charge mode, which can run indefinitely, when the NiCad
batteries are fully charged. See Table 1–9 on page 1–11 for information regarding
the length of time the instrument will operate on batteries.

The message Low Bat is displayed on screen when the remaining battery power
cannot guarantee reliable instrument operation. The length of time the instrument
will continue to operate after this message is displayed is dependent on the
current operating mode of the instrument and the type of batteries installed.

Use the rechargeable NiCad battery pack in full charge and discharge cycles to
optimize the battery life and capacity. Fully discharge the battery pack before
recharging, and then charge the battery pack until it is fully charged. A new
battery pack will take a few charge and discharge cycles to reach full capacity.

Refer to Batteries on page 6–21 for the instructions on how to install and remove
the batteries.

Operational Jumpers and Installed Options. This instrument does not have any
internal operational jumpers or installed options. All instrument configurations
are available through the on-screen menus.

Operating Environment. Refer to Table 1–8 on page 1–10 for the environmental
limits of this instrument.

WFM 90 and WFM 91 Service Manual

2–3

Operating Information

Operating Information

This section will acquaint you with the basic principles of operating this
instrument so that you can service it. Detailed operating instructions are located
in the user manual.

Front Panel Controls

The instrument front panel is illustrated in Figure 2–3.

2–4

Figure 2–3: Instrument front panel

WFM 90 and WFM 91 Service Manual

Operating Information

Power Switch. Press the ON button to toggle the instrument power on and off.
The current instrument keypad and menu selections are saved when the
instrument is turned off using this button.

NOTE. The instrument configuration is not saved if the power source is removed
before the instrument is turned off with this button.

Display Mode Selection. Use the following front-panel buttons to access the
different display modes:

H Press the WFM button to enter the Waveform display mode.
H Press the VECT button to enter the Vector display mode.
H Press the AUDIO button to enter the Audio display mode.
H Press the PIX button to enter the Picture display mode.
H Press the WIP button to enter the Waveform-in-Picture display mode. The

previously selected display mode, other than Picture, is shown in a
1/4-screen-sized window that overlays the Picture display.

Menu Control. Use the following front-panel buttons to enter the different menus:
H Press the MENU button to toggle the Operating menu on and off. The

Operating menu contains monitoring selections which are specifically related
to the currently selected display mode. Operating menu selections include
signal gain and filtering, audio reference levels, and safe action and title
outlines.

H Press the CONFIG button to toggle the Configuration menu on and off. The

Configuration menu contains selections which control overall instrument
monitoring operation. Configuration menu contents include signal and
display controls such as brightness and variable gain. Special modes for
monitoring signal amplitude and managing the battery power consumption
are enabled in this menu.

H Press the LINE SEL button to toggle the Line Select mode on and off and to

display the Line Select menu.

H The four unlabeled buttons directly below the display are referred to as the

Bezel Buttons. These buttons are used to make menu selections and are only
enabled while menus are displayed on screen.

WFM 90 and WFM 91 Service Manual

2–5

Operating Information

Arrow Buttons. The function of the Arrow Buttons is dependent on the current
state of the instrument. For the Waveform and Audio display modes, they control
signal positioning. For the Vector display mode, they control vector phase, with
the

Y and B buttons providing fine adjustment, and the A and " buttons providing

coarse adjustment.
The Arrow Buttons retain their default function for the reduced display when the

Waveform-in-Picture display mode is selected. When the Configuration menu is
displayed, the Y and B buttons operate the menu category selection, while the A
and " buttons retain their default function for the current display mode.

Instrument Reset. Extraordinary conditions may cause the instrument controls to
become locked or to respond erratically. To reset the instrument, first press the
ON button to turn off the power, then press the ON button again while holding
down the WIP and LINE SEL buttons. The instrument should return to normal
operation with the keypad controls and menu selections assigned to the
factory-set defaults.

If this reset does not return the instrument to normal operation, refer to the
Troubleshooting Procedures section of this manual.

Side-panel Connectors

and Switches

The instrument side panels are illustrated in Figure 2–4.

Video Input and Output Connectors. The VIDEO IN and REF IN connectors are
passive BNC inputs, unterminated, and 75W-compensated for a video signal.
Each input has a rear-panel switch to provide an internal 75W signal termination.
The VIDEO OUT connector is a BNC used to output the instrument display to a
remote monitor or video switcher.

Audio Input and Output Connectors. The AUDIO IN connector is a standard
three-pin XLR connector for a single channel of audio input. The audio output
connector is a standard stereo mini headphone jack for the output of the audio
input signal. The mono input signal is heard on both stereo channels. The audio
volume is fixed for each reference level. The larger the displayed signal, the
louder the volume.

2–6

WFM 90 and WFM 91 Service Manual

DC IN 11-18V

Operating Information

Figure 2–4: Instrument side panels

DC Input Power Connector. The DC IN power connector is a 2 mm plug which

accepts a 12 VDC power input, ranging from +11 V to +18 V, using a negative
center lead.

CAUTION. To avoid possible damage to the instrument circuitry when using a DC
power source other than the supplied AC adapter, ensure that the DC source is a
negative-ground +11 V to +18 V system with a negative center lead. The DC
source should be able to provide 12 W of power.

WFM 90 and WFM 91 Service Manual

2–7

Operating Information

Special Operating Modes

The following special operating modes can be activated through the menus:

Amplitude Alarm Mode. The Amplitude Alarm mode provides a means to
automatically monitor the signal amplitude for the Waveform and Audio
displays. This mode is enabled through the Configuration menu.

For the Waveform display mode, the portion of the signal exceeding the 100 IRE
(1.0 V PAL) graticule line is highlighted. For the Audio display mode, the
portion of the signal exceeding the menu-selected reference level is highlighted.
The highlighted portion of the signal is also visible in the Waveform-in-Picture
(WIP) display mode.

Variable Gain Mode. The Variable Gain mode allows you to vary the signal gain
for the Waveform and Vector displays between 45% and 155%. This mode is
enabled through the Configuration menu.

The variable gain adjustment tracks between the Waveform and Vector display
modes and can be adjusted from the Waveform-in-Picture display mode. When
the Variable Gain mode is enabled, the message GAIN UNCAL is displayed in
the on-screen readout.

Time-out Mode. The Time-out mode allows you to automatically shut down the
backlight and/or the instrument after there has been no front-panel activity for a
menu-selected length of time. The Time-out mode enables you to reduce battery
power usage while the instrument is battery powered and also to extend the life
of the backlight bulb. This mode is enabled through the Configuration menu.

2–8

When the backlight times out, the LCD display goes blank and the instrument
appears to be off. The backlight is turned back on by pressing any front panel
button other than the ON button. The backlight shutdown is functional when the
instrument is either battery or DC powered.

When the instrument power times out, the ON button must be pressed to turn the
instrument back on. The instrument power shutdown is only functional when the
instrument is battery powered.

WFM 90 and WFM 91 Service Manual

Operating Information

Calibration Mode. The Calibration mode allows you to adjust the instrument to
factory specifications, if necessary. The Calibration mode is entered by pressing
and holding the CONFIG button for a few seconds. The instrument adjustments
are performed entirely from the front panel with the use of specified input
signals. The instructions for readjusting the instrument to specifications are
located in the Adjustment Procedures section.

CAUTION. Do not attempt to adjust the instrument without using the instructions
listed in the Adjustment Procedures section, or your instrument may not meet the
published specifications.

On-screen Readout

This instrument uses on-screen messages to alert you to certain monitoring
conditions. Figure 2–5 shows the readout messages and their locations.

123

GAIN UNCAL 10uS/DIVEXT REF
MISSING SYNC

100

6

80

60

40

20

0

–20

–40

V1.1

LOW BAT

4

5

Figure 2–5: On-screen readout messages

Readout Description. Listed below are the corresponding descriptions of the

on-screen readout messages:
H The GAIN UNCAL message appears in the Waveform, Vector, and

Waveform-in-Picture display modes when the Variable Gain mode is
turned on.

H The EXT REF message appears in the Waveform and Vector display modes

when the video signal is locking to an external video reference signal.

H The sweep rate is only displayed in the Waveform display mode. There is no

sweep rate readout when 2 Field sweep is selected.

WFM 90 and WFM 91 Service Manual

2–9

Operating Information

H The instrument software version number is displayed when the Configura-

tion menu is open with the DISPLAY category selected.

H The LOW BAT message is displayed when the instrument is battery operated

and the remaining battery power has reached a critically low level. The
remaining length of time that the instrument can be operated reliably is
dependent on the current operating mode.

H The MISSING SYNC message appears in all video display modes when the

signal reference has been lost.

Default Settings

You can reset the front panel and menu settings to the factory-specified default
settings through the Configuration menu. Monitoring adjustments such as signal
position, vector phase, and picture hue are also set. The factory settings are listed
Table 2–1.

T able 2–1: Front panel and menu default settings

Instrument Parameter Factory Default Setting

Display mode Waveform
Signal reference Internal
Filter Flat
DC restorer speed Slow
Gain X1
Variable gain Off
Sweep 2H (2 Line)
Mag Off
Bars 75%
Setup (WFM 90 only) Yes
Alt Phase (WFM 91 only) Off

2–10

Reference dBu 0 dBu
Headroom 3 dB
WIP location Bottom right
Alarms Off
Safe Action Off
Safe Title Off
Vertical shift Off
Backlight time-out Disabled
Instrument time-out Disabled

WFM 90 and WFM 91 Service Manual

Theory of Operation

Theory of Operation

This section contains a module-level description of the instrument circuitry.

Block Diagram Description

The following description is based on the block diagram in Figure 3–1.

Input Board

Top Board

The signal input and output connectors are located on the Input board. There are
receivers for the three inputs, a switch for the video signal reference, and a
variable gain circuit for the audio input.

The video input signal has a DC voltage feedback clamp from the Bottom board.
The video output signal from the Bottom board is routed through the Input
board. The audio variable gain is controlled by the microprocessor serial bus,
which is routed to the Input board from the Top board through the Bottom board.

The Top board contains the microprocessor circuitry, the rasterizer and graphics
generator, the subcarrier oscillator, and the timing generator.

Microprocessor. The microprocessor takes input from the front-panel keypad to
control the operation of the instrument through the serial bus, parallel bus, and
dedicated control lines.

Rasterizer and Graphics. The rasterizer and graphics block produces all internally
generated video including waveforms, graticules, and menus. The rasterizer uses
the horizontal and vertical deflection signals to produce the waveforms. The
rasterizer uses the horizontal and vertical sync signals from the Bottom board to
lock to the incoming video signal.

The rasterizer needs a good analog timing voltage to run correctly. This timing
voltage is generated by a circuit loop between the Top and Bottom boards.
Problems with this circuit can be on either circuit board.

Bottom Board

WFM 90 and WFM 91 Service Manual

The Bottom board contains the power supply circuitry, the horizontal and
vertical deflection circuits, the NTSC or PAL decoder, the vectorscope and
burst-lock circuitry, the sync separator, and the audio amplifier for the headphone
output.

3–1

Theory of Operation

Backlight Power Supply

Board

LCD Display and

Backlight

The Backlight Power Supply board uses the switched DC input voltage from the
batteries or external DC input to generate the voltage for the display backlight.
The backlight mounts into the display module.

The LCD Display module generates the display graphics using input signals
generated on the Top and Bottom boards. The power for the LCD Display
module comes from the Bottom board, while the power for the backlight comes
from the Backlight Power Supply board. The display backlight mounts into the
side of the LCD Display module.

3–2

WFM 90 and WFM 91 Service Manual

Theory of Operation

Video

Out

Video

In

Ext
Ref

Audio

In

Headphone

DC In

11–18 VDC

Battery

Input Board

Fuse

Fuse

Var

Gain

Ref

Bottom Board P/O Top Board

Clamp

LPF

Vert
Defl

Horiz

Defl

Rasterizer

and

Graphics

Video

Out

Video In

Audio

Burst

Lock

RGB from
Rasterizer
and Graphics

Fsc

R–Y

Vectorscope
(Including Ø

shifter)

RGB

Front

Panel

Keys

Part of

mP

Instrument

Control

Power Supply

and Battery

NTSC (or PAL)

Decoder (Self

regenerator)

Control DAC

(16 analog

Outputs)

Charger

contained
subcarrier

16

Sync

Separator

±8 VDC
+5 VDC

Vector
±8 VDC
+5 VDC

Subcarrier

Oscillator

Timing

B–Y

Sweep

P/O Top Board

Part of

mP

Timing

Trig

DSync

RGB

Display

Brightness

and View

2

Adjust

RGB

LCD Display

and Backlight

Backlight

Power

Supply

Board

Sel Vid

Backlight
Brightness

Figure 3–1: Simplified block diagram

WFM 90 and WFM 91 Service Manual

3–3

Theory of Operation

3–4

WFM 90 and WFM 91 Service Manual

Performance Verification

Performance Verification

This section contains the following information:

H Summary verification procedure
H List of equipment required to perform the procedures
H Performance verification procedures

Summary Verification

The summary verification is listed in Table 4–1 and is intended for those who are
familiar with the complete performance verification procedures. Procedure titles
and page numbers provide a cross-reference to the performance verification
procedures on the following pages.

T able 4–1: Summary verification procedure

Procedure Procedure Requirement Page #

Preliminary setup Initial equipment connections and control settings. 4–5
Sync separation Signal synchronization will occur with input signals of composite video or

black burst, with sync amplitudes of 40 IRE (300 mV PAL) "6 dB for
internal reference, and sync amplitudes of between 143 mV and 4 V for
external reference.

Sweep timing and integral linearity Sweep Timing Accuracy: 5 ms/Div. (1 Line), 10 ms/Div. (2 Line), and

1.0 ms/Div . (2 Line + MAG), "2%. 0.2 ms/Div. (1 Line + MAG) "3%.
Integral Linearity: "1%.

Vertical gain and vertical magnifier registration 1 Volt Full Scale: 1 V input displayed within 1% of 140 IRE (1.00 V PAL).

X5 Gain: Gain accuracy within 5% with 1 V input signal. X5 Gain
Registration: v1 major division of vertical shift from baseline between
unmagnified and magnified signal.

Variable gain range and vertical position range Variable Gain Range: Input signals between 0.8 V and 2 V can be

adjusted to 140 IRE (1.0 V) display. 160 mV and 400 mV for X5 Gain.
Vertical Position Range: 1 V signal can be positioned so that peak white
and sync tip can be placed at blanking level, with the DC Restorer Clamp
on, regardless of gain setting.

Overscan v2% variation in baseline of 100 IRE (700 mV PAL) 12.5T (20T PAL)

modulated pulse as it is positioned over the middle 80% of the screen.

Input and DC restorer frequency response X1 Gain Response (Flat filter selected): 50 kHz to 6 MHz within 2% of

response at 50 kHz. X5 Gain Response (Flat filter selected): 50 kHz to 6
MHz within 5% of response at 50 kHz. Attenuation of 60 Hz (50 Hz PAL)
on Input Signal: SLOW mode: v20%. FAST mode: w90%.

4–5

4–6

4–7

4–7

4–8

4–9

WFM 90 and WFM 91 Service Manual

4–1

Performance Verification

T able 4–1: Summary verification procedure (Cont.)

Procedure Page #Procedure Requirement

Vector phase stability Phase Shift with Subcarrier Frequency Change from FSC to FSC 50 Hz

10 Hz PAL): 2°. Phase Shift with Burst Amplitude Change from

(F

SC

Nominal to 6 dB: 2°. Phase Shift with V ariable Gain Control Varied
from +3 dB to –6 dB: 1°.

Chrominance bandwidth Chrominance Bandwidth: Upper –3 dB Point: FSC + 500 kHz, 100 kHz.

Lower –3 dB Point: F

Audio gain and frequency response Measurement Accuracy: 0.5 dB at 1 kHz. Frequency Response: 0.5 dB

from 50 Hz to 20 kHz.

– 500 kHz, 100 kHz.

SC

Equipment Required

Table 4–2 lists the required equipment and accessory items to perform the
performance verification procedures. Minimum equipment specifications are
followed by an example of equipment that meet these specifications.

An accuracy ratio of 4:1 or better for the warranted specifications will be
obtained using the equipment recommended in Table 4–2 with the following
exceptions:

H Audio Amplitude: 2.5:1
H Audio Flatness: 2.5:1

4–11

4–1 1

4–13

T able 4–2: Equipment required for performance verification

Equipment Description Minimum Requirements Equipment Example

Television test signal generator Color test signals for the television standard of

the monitor to be tested: color bar signal, pulse
and bar; with 2T pulse, 2T bar, and modulated
pulse, field square wave signal, and black burst
signal

Leveled sine wave generator Output Level Range: –11.55 dBm (200 mV) to

0.43 dBm (800 mV);
Frequency: 50 kHz to 10 MHz

Function generator Range: 0.1 to 5 Vpp when loaded by 75 W,

10 Vpp when unloaded;
Frequency: 50 kHz to 10 MHz.

Audio generator Amplitude Range: –10 dBu to 8 dBu;

Frequency: 1 kHz to 50 kHz

Voltmeter Range: 0 VDC to 100 VDC;

Accuracy: 0.1%

4–2

NTSC: Tektronix 14101 TV Test Signal Generator
with Option AA and Option AB (modified SPG2
and TSG7), TSG3, and TSG5
PAL: Tektronix 14111 TV Test Signal Generator
with Option AA and Option AB (modified SPG12
and TSG17), TSG13, and TSG15

Tektronix SG 5032 Leveled Sine Wave Generator

Tektronix FG 5032 Function Generator

Tektronix ASG 100 Audio Signal Generator

Tektronix DM 504A2 Digital Multimeter

WFM 90 and WFM 91 Service Manual

T able 4–2: Equipment required for performance verification (Cont.)

Equipment Description Equipment ExampleMinimum Requirements

Performance Verification

Frequency counter Range: 10 Hz to 10 MHz;

Tektronix DC 503A2 Universal Counter

Accuracy: 0.001%

Video amplitude calibrator
(VAC)

Signal: Adjustable square wave 0.0 mVpp to

999.9 mVpp; Resolution: 0.1 mV; Accuracy:

Tektronix part number 067-0916-00

2

0.05%; Frequency: Approximately 270 Hz

Peak-to-peak detector Input Signal Range: 0.25 Vpp to 1.0 Vpp;

Flatness: 0.2% 50 kHz to 10 MHz;
Input Impedance: 75 W

Tektronix part number 015-0408-00 (includes
peak-to-peak detector head, Tektronix part
number 015-0413-00)

2

75 W terminator Two required; feed-through type Tektronix part number 011-0103-02
75 W coaxial cable Two cables required, male to male BNC

Tektronix part number 012-0159-00 (42-inch)

connectors
50 W coaxial cable 1% precision, male to male BNC connectors Tektronix part number 012-0482-00 (36-inch)
Audio cable XLR female to XLR male Switchcraft part number SC3XXJ
50 W-to-75 W minimum loss

attenuator

Impedance: 50 W-to-75 W; Tolerance: 0.5 dB;

Frequency: 100 MHz

Tektronix part number 011-0057-00

X10 attenuator 75 W Tektronix part number 011-0061-00
Dual input coupler Matched BNC cable-T for making phase

Tektronix part number 067-0525-02
comparisons between two inputs; Matched
length of the two arms within 0.1 inch

BNC female to BNC female

Tektronix part number 103-0028-00

connector

1

The 1410-Series generators with standard SPG and TSG modules can be used, but not all checks and adjustments can be
made. The standard SPG2 and SPG12 modules will not check lock to changes in sync amplitude, cw lock to changes in
burst amplitude, and frequency lock to burst offset frequency changes. The signal generator can be ordered with one or
both options (AA and AB). The TSG3 and TSG13 are Modulated Staircase Generators with variable APL. The TSG5 and
TSG15 are Pulse and Bar Generators with modulated pulse and field square wave signals.

2

Requires a Tektronix TM500-Series or TM 5000-Series Power Module Mainframe.

WFM 90 and WFM 91 Service Manual

4–3

Performance Verification

Performance V erification Procedures

Perform the performance verification procedures to ensure that the instrument is
operating properly and is meeting the performance requirements listed in the
characteristic tables of the Specifications section.

Conventions

Throughout these procedures the following conventions apply:
H Each verification procedure uses the following format:

Title of verification procedure
Specification requirement(s) the procedure is verifying
Verification procedure

H When you are instructed to use a front-panel control or to select a specific

menu item of the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture,
and Audio Monitor, the name of the control or menu item appears in
boldface type.

NOTE. Do not make changes to the front-panel settings or controls that are not
called out in the procedures. Each procedure will require you to set the
instrument to certain default settings before verifying the procedure r equirement.
If you make changes to these settings, other than those called out in the
procedure, you may obtain invalid results.

The verification procedures are written in a format that assumes you ar e
performing the procedures in sequential order from the beginning. If you are
unsure about equipment hookups or instrument settings for a specific procedure,
you will need to review the previous procedures to verify the hookups and
settings required for the current procedure.

4–4

Prerequisites

The tests in this section comprise a valid confirmation of instrument performance
when the following requirements are met:

H Test equipment used to verify performance requirements must be calibrated

and working within the limits specified in Table 4–2 on page 4–2.

H The WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and Audio

Monitor must have last been adjusted at an ambient temperature range of
+20° C to +30° C, and must have been operating for a warm-up period of at
least 20 minutes.

WFM 90 and WFM 91 Service Manual

Performance Verification

Preliminary Setup

Sync Separation

Perform the following steps before beginning the verification procedures:

1. Plug the AC power adapter into the instrument and then plug the adapter into

the AC power source.

2. Connect the multiburst signal from the television signal generator through a
75 W in-line terminator and dual-input coupler to the VIDEO IN and
REF IN connectors on the WFM 90 or WFM 91 Handheld Waveform,
Vector, Picture, and Audio Monitor.

3. Set the input termination switches to the HIZ position.

4. Turn on the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and

Audio Monitor.

5. Enter the Configure menu. Select PRESETS and then select DEFAULT.

NOTE. Be sure you have warmed up the instrument for at least 20 minutes before
you perform any of the verification procedures.

This procedure verifies the following requirement:
Signal synchronization will occur with input signals of composite video or black

burst, with sync amplitudes of 40 IRE (300 mV PAL) 6 dB for internal
reference, and sync amplitudes of between 143 mV and 4 V for external
reference.

1. Enter the Configuration menu and select the INPUT category.

2. Check for a stable display while switching between INT and EXT REF.

3. Remove the terminator from the dual-input coupler.

4. Check for a stable display while switching between INT and EXT REF.

5. Add three 75 W terminators to the dual-input coupler.

6. Check for a stable display while switching between INT and EXT REF.

7. Select INT REF from the Configuration menu INPUT category.

8. Remove the dual-input coupler from the instrument.

WFM 90 and WFM 91 Service Manual

4–5

Performance Verification

Sweep Timing and Integral

Linearity

This procedure verifies the following requirement:
Sweep Timing Accuracy: 5 ms/Div. (1 Line), 10 ms/Div. (2 Line), and 1.0 ms/Div.

(2 Line + MAG), 2%. 0.2 ms/Div. (1 Line + MAG) 3%. Integral Linearity:
1%.

1. Connect the multiburst signal from the television signal generator to the
VIDEO IN connector on the WFM 90 or WFM 91 Handheld Waveform,

Vector, Picture, and Audio Monitor, and to the input on the frequency
counter, using a T-connector, 75 W cable, and 75 W in-line terminator.

2. Set the multiburst generator controls to Low, Continuous, and Manual. Set
the output frequency to 100 kHz (as read on the frequency counter).

3. Check for one cycle per division, 1 minor division, over the center ten
graticule divisions.

4. Select 1H SWEEP from the Operating menu.

5. Set the multiburst generator frequency to 200 kHz.

6. Check for one cycle per division, 1 minor division, over the center ten

graticule divisions.

7. Adjust the multiburst generator frequency so that the cycles land exactly on
the first and tenth graticule marks.

8. Check that each cycle is within 0.5 minor division of a major graticule
mark.

9. Select MAG ON from the Operating menu.

10. Set the multiburst generator frequency to 2 MHz.

11. Check for one cycle per division, 1 minor division, over the center ten

graticule divisions, and also at both ends of the magnified sweep (using the
horizontal position control), ignoring the first and last cycle.

12. Set the multiburst generator frequency to 1 MHz.

13. Select 2H SWEEP from the Operating menu.

14. Check for one cycle per division, 1 minor division, over the center ten

graticule divisions, and also at both ends of the magnified sweep (using the
horizontal position control), ignoring the first and last cycle.

15. Select MAG OFF from the Operating menu.

4–6

WFM 90 and WFM 91 Service Manual

Performance Verification

Vertical Gain and Vertical

Magnifier Registration

This procedure verifies the following requirement:
1 Volt Full Scale: 1 V input displayed within 1% of 140 IRE (1.00 V PAL).

X5 Gain: Gain accuracy within 5% with 1 V input signal. X5 Gain Registration:
1 major division of vertical shift from baseline between unmagnified and
magnified signal.

1. Set the multiburst generator controls to Composite and Multiburst.

2. Position the signal baseline to the graticule baseline, and then select
X5 GAIN from the Operating menu.

3. Check that the signal baseline is within 1 major division of the graticule

baseline.

4. Select X1 GAIN from the Operating menu.

5. Remove the signal and terminator from the VIDEO IN connector.

6. Connect the output of the VAC to the VIDEO IN connector. Do not

terminate the input.

7. Set the VAC for a 999.9 mV output, with all of the buttons out except for
+LUM and NTSC (PAL button for the WFM 91).

8. Check for a display amplitude of 140 IRE 1.4 IRE (1000 mV 10 mV
PAL).

Variable Gain Range and

Vertical Position Range

9. Set the VAC for a 199.9 mV output.

10. Select X5 GAIN from the Operating menu.

11. Check for a display amplitude of 140 IRE 5 IRE (1000 mV 50 mV

PAL).

12. Select X1 GAIN from the Operating menu.

This procedure verifies the following requirement:
Variable Gain Range: Input signals between 0.8 V and 2 V can be adjusted to

140 IRE (1.0 V) display. 160 mV and 400 mV for X5 Gain. Vertical Position
Range: 1 V signal can be positioned so that peak white and sync tip can be
placed at blanking level, with the DC Restorer Clamp on, regardless of gain
setting.

1. Set the VAC for a 999.9 mV output.

2. Select VAR GAIN ON from the Configuration menu.

3. Check by adjusting the Variable Gain controls that the signal amplitude can

be displayed less than 70 IRE (500 mV PAL).

WFM 90 and WFM 91 Service Manual

4–7

Performance Verification

4. Set the VAC for a 799.9 mV output.

5. Check by adjusting the Variable Gain controls that the signal amplitude can

be displayed greater than 140 IRE (1000 mV PAL).

6. Select X5 GAIN from the Operating menu.

7. Set the VAC for a 399.9 mV output.

8. Enter the Configuration menu and select the VAR GAIN category.

9. Check by adjusting the Variable Gain controls that the signal amplitude can

be displayed less than 140 IRE (1000 mV PAL).

10. Set the VAC for a 159.9 mV output.

11. Check by adjusting the Variable Gain controls that the signal amplitude can

be displayed greater than 140 IRE (1000 mV PAL).

12. Replace the VAC signal on the VIDEO IN connector with a pulse and bar

signal using a 75 W in-line terminator.

Overscan

13. Check by adjusting the Vertical Position controls, that the white bar and

sync tip portions of the signal can be adjusted to the graticule baseline.

14. Select VAR GAIN OFF from the Configuration menu.

15. Select X1 GAIN from the Operating menu.

This procedure verifies the following requirement:
2% variation in baseline of 100 IRE (700 mV PAL) 12.5T (20T PAL)

modulated pulse as it is positioned over the middle 80% of the screen.

1. Check that the amplitude of the sine wave at the bottom of the mod pulse
varies less than 2% while using the Vertical Position controls to position the
signal over the middle 80% of the graticule.

2. Remove the pulse and bar signal from the VIDEO IN connector.

4–8

WFM 90 and WFM 91 Service Manual

Performance Verification

Input and DC Restorer

Frequency Response

This procedure verifies the following requirement:
X1 Gain Response (Flat filter selected): 50 kHz to 6 MHz within 2% of response

at 50 kHz. X5 Gain Response (Flat filter selected): 50 kHz to 6 MHz within 5%
of response at 50 kHz. Attenuation of 60 Hz (50 Hz PAL) on Input Signal:
SLOW mode: v20%. FAST mode: w90%.

1. Select EXT REF from the Configuration menu.

2. Connect the 50 W precision cable from the output of the leveled sine wave

generator to the dual-input coupler using a 50 W-to-75 W minimum loss
attenuator.

3. Connect one side of the dual-input coupler to the VIDEO IN connector.

4. Connect the 015-0413-00 Peak-to-Peak Detector Head to the other end of the

dual-input coupler, using the female-to-female BNC connector. Connect the
other end of the Peak-to-Peak Detector Head to the 015-0408-00 Peak-to­Peak Detector + Input.

5. Connect the peak-to-peak detector Output to the digital multimeter or

oscilloscope.

6. Set the leveled sine wave generator frequency to 50 kHz and adjust the

generator amplitude for exactly 100 IRE (700 mV PAL) of display.

7. Adjust the peak-to-peak detector Plus amplifier and input control until the

green LED is on.

8. Note the digital multimeter readout level or the oscilloscope dc level.

9. Set the sine wave generator frequency to 3.58 MHz (4.43 MHz PAL).

10. Adjust the sine wave generator amplitude for exactly 100 IRE (700 mV

PAL) of display.

11. Check that the digital multimeter readout level, or the oscilloscope dc level

is within "14 mV of the reading noted in step 8.

12. Set the sine wave generator frequency to 6 MHz.

13. Adjust the sine wave generator amplitude for exactly 100 IRE (700 mV

PAL) of display.

14. Check that the digital multimeter readout level or the oscilloscope dc level,

is within "14 mV of the reading noted in step 8.

15. Set the sine wave generator frequency to 50 kHz.

16. Select X5 GAIN from the Operating menu.

WFM 90 and WFM 91 Service Manual

4–9

Performance Verification

17. Adjust the peak-to-peak detector Plus amplifier and input control fully
counterclockwise.

18. Adjust the sine wave generator for a display amplitude of 100 IRE (700 mV
PAL).

19. Note the digital multimeter readout level or the oscilloscope dc level.

20. Set the sine wave generator frequency to 3.58 MHz (4.43 MHz PAL).

21. Adjust the sine wave generator amplitude for exactly 100 IRE (700 mV

PAL) of display.

22. Check that the digital multimeter readout level, or the oscilloscope dc level,
is within "7 mV of the reading noted in step 19.

23. Set the sine wave generator frequency to 6 MHz.

24. Adjust the sine wave generator amplitude for exactly 100 IRE (700 mV

PAL) of display.

25. Check that the digital multimeter readout level, or the oscilloscope dc level,
is within "7 mV of the reading noted in step 19.

26. Select X1 GAIN from the Operating menu.

27. Remove the dual-input coupler from the instrument.

28. Connect the function generator output to the VIDEO IN connector using a

X10 (75 W) attenuator.

29. Select 1H SWEEP from the Operating menu.

30. Enter the Configuration menu and select the INPUT category. Select
EXT REF and SLOW DC REST.

31. Set the function generator to output a 60 Hz (50 Hz PAL) sine wave with a

display amplitude of 100 IRE (700 mV PAL) on the WFM 90 or WFM 91
Handheld Waveform, Vector, Picture, and Audio Monitor.

32. Connect a black burst signal to the REF IN connector. Do not terminate the
input.

33. Check that the display amplitude is w80 IRE (560 mV PAL).

34. Select FAST DC REST.

4–10

35. Check that the display amplitude is v10 IRE (70 mV PAL).

36. Select INT REF and SLOW DC REST from the Configuration menu.

37. Remove all input signals from the WFM 90 or WFM 91 Handheld Wave-

form, Vector, Picture, and Audio Monitor.

WFM 90 and WFM 91 Service Manual

Performance Verification

Vector Phase Stability

This procedure verifies the following requirement:
Phase Shift with Subcarrier Frequency Change from F

10 Hz PAL): 2°. Phase Shift with Burst Amplitude Change from

(F

SC

to FSC 50 Hz

SC

Nominal to 6 dB: 2°. Phase Shift with Variable Gain Control Varied from
+3 dB to –6 dB: 1°.

1. Connect a 75% color bar signal to the VIDEO IN connector. Set the input
switch to the 75 W position.

2. Select VECTOR display mode on the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor.

3. Use the Phase controls to position the burst vector on the 180° graticule line.

4. Check that when the television generator subcarrier frequency is changed

50 Hz (10 Hz PAL) from nominal, that the display locks, and that the
burst phase has changed 2° or less.

5. Return the subcarrier frequency to nominal on the television signal generator.

6. Replace the color bar signal on the VIDEO IN connector with a black burst

signal.

7. Check that the vector phase changes less than 2° while varying the burst
amplitude from nominal to 6 dB (1/2 to 2X amplitude), using the
television signal generator burst amplitude control.

Chrominance Bandwidth

8. Return the burst amplitude to nominal on the television signal generator.

9. Select VAR GAIN ON from the Configuration menu.

10. Check that the vector phase changes less than 1° while varying the vector

burst amplitude from 1/2 to 1.5 times nominal amplitude using the variable
gain control.

11. Select VAR GAIN OFF from the Configuration menu.

12. Remove the signal input from the VIDEO IN connector.

This procedure verifies the following requirement:
Chrominance Bandwidth: Upper –3 dB Point: F

Lower –3 dB Point: F

– 500 kHz, 100 kHz.

SC

+ 500 kHz, 100 kHz.

SC

1. Connect the precision 50 W cable to the output of the leveled sine wave
generator. Connect the other end of the cable to the 50 W to 75 W minimum-
loss attenuator, and then connect the attenuator to the VIDEO IN connector.

2. Select EXT REF from the Configuration menu.

WFM 90 and WFM 91 Service Manual

4–11

Performance Verification

3. Set the leveled sine wave generator frequency to 3.58 MHz (4.43 MHz PAL)

and adjust the amplitude control so that the circle overlays the graticule
compass rose.

4. Decrease the frequency on the leveled sine wave generator until the edge of

the circle display reaches the –3 dB (70%) gaps on the vertical graticule axis.
See Figure 4–1.

Compass rose–3 dB Points

Figure 4–1: –3 dB marks on the vector graticule

5. Check that the frequency readout on the leveled sine wave generator is

between 2.98 and 3.18 MHz (3.83 and 4.03 MHz PAL).

6. Adjust the frequency on the leveled sine wave generator until the edge of the

circle display reaches the –3 dB (70%) point gaps on the horizontal graticule
axis.

7. Check that the frequency readout on the leveled sine wave generator is

between 2.98 and 3.18 MHz (3.83 and 4.03 MHz PAL).

8. Increase the frequency on the leveled sine wave generator until the edge of

the circle display expands out to the compass rose and again reduces to the
–3 dB (70%) point gaps on the vertical graticule axis. See Figure 4–1.

9. Check that the frequency readout on the leveled sine wave generator is

between 3.98 and 4.18 MHz (4.83 and 5.03 MHz PAL).

10. Adjust the frequency on the leveled sine wave generator until the edge of the

circle display reaches the –3 dB (70%) point gaps on the horizontal graticule
axis.

4–12

WFM 90 and WFM 91 Service Manual

Performance Verification

11. Check that the frequency readout on the leveled sine wave generator is
between 3.98 and 4.18 MHz (4.83 and 5.03 MHz PAL).

12. Remove all signals from the WFM 90 or WFM 91 Handheld Waveform,
Vector, Picture, and Audio Monitor.

Audio Gain and

Frequency Response

This procedure verifies the following requirement:
Measurement Accuracy: 0.5 dB at 1 kHz. Frequency Response: 0.5 dB from

50 Hz to 20 kHz.

1. Connect the output from the audio generator to the AUDIO IN connector on
the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and Audio
Monitor.

2. Set the audio generator for a 1 kHz tone output, with an amplitude of
+8.0 dBu. Select Signal On.

3. Select AUDIO display mode on the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor.

4. Enter the Operating menu and select 8 dBu.

5. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

6. Set the audio generator for a +4.0 dBu output amplitude.

7. Select 4 dBu from the Operating menu.

8. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

9. Set the audio generator for a 0.0 dBu output amplitude.

10. Select 0 dBu from the Operating menu.

11. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

12. Set the audio generator for a –10.0 dBu output amplitude.

13. Select –10 dBu from the Operating menu.

14. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

WFM 90 and WFM 91 Service Manual

4–13

Performance Verification

15. Set the audio generator for a 50 Hz tone output, with an amplitude of

+8.0 dBu.

16. Select 8 dBu from the Operating menu.

17. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

18. Set the audio generator frequency to 5 kHz.

19. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

20. Set the audio generator frequency to 10 kHz.

21. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

22. Set the audio generator frequency to 15 kHz.

23. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

24. Set the audio generator frequency to 20 kHz.

25. Check that the display amplitude is within 0.5 dB of the reference level

graticule lines.

4–14

WFM 90 and WFM 91 Service Manual

Adjustment Procedures

Adjustment Procedures

This section contains the following information:

H Summary adjustment procedure
H List of equipment required to perform the procedures
H Adjustment procedures

Summary Adjustment

Table 5–1 is the summary adjustment procedure and is intended for those who
are familiar with the complete adjustment procedures. Adjustment titles and page
numbers provide a cross-reference to the adjustment procedures on the following
pages.

T able 5–1: Summary adjustment

Adjustment Page #

Preliminary setup 5–4
Raster VCO 5–4
Sweep timing and horizontal mag registration 5–5
Vertical gain and X5 gain registration 5–6
Frequency response 5–7
Vector quadrature phase 5–8
Vector gain and X5 gain phase 5–9
Audio gain 5–10

WFM 90 and WFM 91 Service Manual

5–1

Adjustment Procedures

Equipment Required

Table 5–2 lists the required equipment and accessory items to perform the
adjustment procedures. Minimum equipment specifications are followed by an
example of equipment that meet these specifications.

T able 5–2: Equipment required for performance verification

Equipment Description Minimum Requirements Equipment Example

Television test signal generator 75% color bar test signal for the television

standard of the monitor to be tested

Leveled sine wave generator Output Level Range: –11.55 dBm (200 mV) to

0.43 dBm (800 mV);
Frequency: 50 kHz to 10 MHz

Function generator Range: 0.1 to 5 Vpp when loaded by 75 W,

10 Vpp when unloaded;
Frequency: 50 kHz to 10 MHz.

Audio generator Amplitude Range: –10 dBu to 8 dBu;

Frequency: 1 kHz to 50 kHz

Voltmeter Range: 0 VDC to 100 VDC;

Accuracy: 0.1%

Frequency counter Range: 10 Hz to 10 MHz;

Accuracy: 0.001%

Video amplitude calibrator
(VAC)

Peak-to-peak detector Input Signal Range: 0.25 Vpp to 1.0 Vpp;

75 W terminator One required; feed-through type Tektronix part number 011-0103-02
75 W coaxial cable Three cables required, male-to-male BNC

50 W coaxial cable 1% precision, male-to-male BNC connectors Tektronix part number 012-0482-00 (36-inch)
Dual input coupler Matched BNC cable-T for making phase

Audio cable XLR female to XLR male Switchcraft part number SC3XXJ
50 W-to-75 W minimum loss

attenuator
BNC female to BNC female

connector
BNC female to dual banana

adapter

1

Requires a Tektronix TM500-Series or TM 5000-Series Power Module Mainframe.

Signal: Adjustable square wave 0.0 mVpp to

999.9 mVpp; Resolution: 0.1 mV; Accuracy:

0.05%; Frequency: Approximately 270 Hz

Flatness: 0.2% 50 kHz to 10 MHz;
Input Impedance: 75 W

connectors

comparisons between two inputs; Matched
length of the two arms within 0.1 inch

Impedance: 50 W-to-75 W; Tolerance: 0.5 dB;
Frequency: 100 MHz

NTSC: Tektronix TSG 100;
PAL: Tektronix TSG 11 1

Tektronix SG 5031 Leveled Sine Wave Generator

Tektronix FG 5031 Function Generator

Tektronix ASG 100 Audio Signal Generator

Tektronix DM 504A1 Digital Multimeter

Tektronix DC 503A1 Universal Counter

Tektronix part number 067-0916-00

Tektronix part number 015-0408-00 (includes
peak-to-peak detector head, Tektronix part
number 015-0413-00)

Tektronix part number 012-0159-00 (42-inch)
Tektronix part number 012-1339-00 (24-inch)

Tektronix part number 067-0525-02

Tektronix part number 011-0057-00

Tektronix part number 103-0028-00

Tektronix part number 103-0090-00

1

1

5–2

WFM 90 and WFM 91 Service Manual

Adjustment Procedures

Adjustment Procedures

The WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and Audio
Monitor does not have any internal adjustments. Instrument adjustments are
made entirely from the front panel by assigning adjustment functions to the
Arrow Buttons through the Calibration menu.

Conventions

Throughout these procedures the following conventions apply:
H Each adjustment procedure uses the following format:

Title of adjustment procedure
Adjustment procedure

H When you are instructed to use a front-panel control or to select a specific

menu item of the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture,
and Audio Monitor, the name of the control or menu item appears in
boldface type.

NOTE. Do not make changes to the front-panel settings or controls that are not
called out in the procedures. Each procedure will require you to set the
instrument to certain default settings before an adjustment is made. If you make
changes to these settings, other than those called out in the procedure, you may
incorrectly adjust your instrument.

The adjustment procedures are written in a format that assumes you are
performing the procedures in sequential order from the beginning. If you are
unsure about equipment hookups or instrument settings for a specific procedure,
you will need to review the previous procedures to verify the hookups and
settings required for the current procedure.

Prerequisites

WFM 90 and WFM 91 Service Manual

The adjustments in this section comprise a valid readjustment of instrument
performance when the following requirements are met:

H Test equipment used to verify performance requirements must be calibrated

and working within the limits specified in Table 5–2 on page 5–2.

H The WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and Audio

Monitor must have been adjusted at an ambient temperature range of +20° C
to +30° C, and must have been operating for a warm-up period of at least
20 minutes.

5–3

Adjustment Procedures

Adjustment Methodology

Preliminary Setup

The following information provides you with an overview of how adjustments
are made on the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and
Audio Monitor.

Calibration Menu. To enter the Calibration menu, press and hold the CONFIG
button for a few seconds. The Calibration menu display consists of a list of
instrument adjustments along with two action selections, CAL and SAVE. Select
CAL to enable the adjustment that is currently selected from the list of adjust­ments. SAVE must be selected after every adjustment to save the adjustment in
memory.

NOTE. SAVE must be selected from the Calibration menu after each adjustment
is completed to save the adjustment in memory. If an adjustment is not saved, the
instrument will revert to the original adjustment setting on the next power-up.

After you have enabled an adjustment, select CAL MENU to return the display
to the main Calibration menu. Most adjustments provide a POS or PHASE menu
selection, which allows you to toggle the Arrow Buttons between the selected
adjustment and signal positioning to aid in performing the adjustment.

Perform the following steps to prepare the instrument to be adjusted:

Raster VCO

1. Plug the AC power adapter into the WFM 90 or WFM 91 Handheld

Waveform, Vector, Picture, and Audio Monitor, and then plug the adapter
into the AC power source.

2. Set the input termination switches to the HIZ position on the WFM 90 or

WFM 91 Handheld Waveform, Vector, Picture, and Audio Monitor.

3. Connect a 75% color bar signal from the television signal generator to the
VIDEO IN connector, using a 75 W in-line terminator.

4. Turn on the instrument.

5. Press the CONFIG button. Select PRESETS, and then select DEFAULT.

Perform the following steps to adjust the raster VCO:

1. Select RAST VCO from the Calibration menu.

2. Select CAL, and then select AUTO.

3. Wait until the CANCEL message disappears from the screen.

4. Select CAL MENU, and then select SAVE from the menu.

5–4

WFM 90 and WFM 91 Service Manual

Adjustment Procedures

Sweep Timing and

Horizontal Mag

Registration

Perform the following steps to adjust the sweep timing and horizontal mag
registration:

1. Replace the signal on the VIDEO IN connector with the output from the

function generator. Be sure to use a 50 W-to-75 W minimum-loss attenuator
and a precision (1%) 50 W cable if the generator specifies a 50 W output.

2. Set the function generator for a 200 kHz sine wave output.

NOTE. Verify the generator frequencies used in these steps by checking them on
the frequency counter.

3. Select 1H SWEEP from the Operating menu.

4. Select 1H SWEEP from the Calibration menu, and then select CAL.

5. Adjust the Arrow Buttons for one cycle per major division.

6. Select CAL MENU, and then select SAVE.

7. Set the function generator frequency to 100 kHz.

8. Select 2H SWEEP from the Operating menu.

9. Select 2H SWEEP from the Calibration menu, and then select CAL.

10. Adjust the Arrow Buttons for one cycle per major division.

11. Select CAL MENU, and then select SAVE.

12. Replace the signal on the VIDEO IN connector with the output from the

leveled sine wave generator. Use the 50 W-to-75 W minimum-loss attenuator
and precision (1%) 50 W cable if the generator specifies a 50 W output.

13. Set the sine wave generator for a 1 MHz output.

14. Select MAG ON from the Operating menu.

15. Select MAG GAIN from the Calibration menu, and then select CAL.

16. Adjust the Arrow Buttons for one cycle per major division.

17. Select CAL MENU, and then select SAVE.

18. Select MAG OFF from the Operating menu.

19. Replace the signal on the VIDEO IN connector with a 75% color bar signal

from the television signal generator, using a 75 W in-line terminator.

20. Select 2F SWEEP from the Operating menu.

21. Select 2F SWEEP from the Calibration menu, and then select CAL.

WFM 90 and WFM 91 Service Manual

5–5

Adjustment Procedures

22. Adjust the Arrow Buttons for a sweep length of 12 major divisions.

23. Select CAL MENU, and then select SAVE.

24. Select 2H SWEEP from the Operating menu.

25. Select MAG REG from the Calibration menu, and then select CAL.

26. Select POS, and then use the Arrow Buttons to position the falling edge of

sync to the center graticule tick mark.

27. Select MAG ON, and then select MAG REG.

28. Adjust the Arrow Buttons to reposition the falling edge of sync to the center

graticule tick mark.

29. Select MAG OFF.

30. Select CAL MENU, and then select SAVE.

Vertical Gain and X5 Gain

Registration

Perform the following steps to adjust the vertical gain and X5 gain registration:

1. Replace the signal on the VIDEO IN connector with the output from the
VAC. Do not terminate the input.

2. Set the VAC for a 999.9 mV output with all of the buttons out except +LUM
and NTSC (PAL button for the WFM 91).

3. Select X1 GAIN from the Calibration menu, and then select CAL.

4. Adjust the Arrow Buttons for a display amplitude of exactly 140 IRE

(1000 mV PAL).

5. Select CAL MENU, and then select SAVE.

6. Set the VAC for a 199.9 mV output.

7. Select X5 GAIN from the Operating menu.

8. Select X5 GAIN from the Calibration menu, and then select CAL.

9. Adjust the Arrow Buttons for a display amplitude of exactly 140 IRE

(1000 mV PAL).

10. Select CAL MENU, and then select SAVE.

5–6

11. Replace the signal on the VIDEO IN connector with a 75% color bar signal
from the television signal generator, using a 75 W in-line terminator.

12. Select X5 POS from the Calibration menu, and then select CAL.

13. Select X1 GAIN, and then position the signal baseline to the graticule

baseline.

WFM 90 and WFM 91 Service Manual

Adjustment Procedures

14. Select X5 GAIN from the Calibration menu, and then select X5 POS.

15. Adjust the Arrow Buttons to reposition the signal baseline back to the

graticule baseline.

16. Select X1 GAIN from the Calibration menu.

17. Select CAL MENU, and then select SAVE.

18. Remove the signal and terminator from the VIDEO IN connector.

Frequency Response

Perform the following steps to adjust the frequency response:

1. Connect a 50 W precision cable from the output of the leveled sine wave

generator to the dual-input coupler using a 50 W-to-75 W minimum loss
attenuator.

2. Connect one side of the dual-input coupler to the VIDEO IN connector.

3. Connect the 015-0413-00 Peak-to-Peak Detector Head to the other end of the

dual-input coupler, using the female-to-female BNC connector.

4. Connect the other end of the Peak-to-Peak Detector Head to the 015-0408-00

Peak-to-Peak Detector + Input.

5. Connect the peak-to-peak detector Output to the digital multimeter, or an

oscilloscope.

6. Select EXT REF from the Configuration menu.

7. Set the leveled sine wave generator frequency to 50 kHz and adjust the

generator amplitude for exactly 100 IRE (700 mV PAL) of display.

8. Adjust the peak-to-peak detector Plus amplifier and input control until the

green LED is on.

9. Note the digital multimeter readout level or the oscilloscope dc level.

10. Set the sine wave generator frequency to 3.58 MHz (4.43 MHz PAL).

11. Adjust the amplitude of the sine wave generator so that the digital multime-

ter readout, or oscilloscope level, matches that noted in step 9.

12. Select X1 FREQ from the Calibration menu, and then select CAL.

13. Adjust the Arrow Buttons for a display amplitude of exactly 100 IRE

(700 mV PAL).

14. Select CAL MENU, and then select SAVE.

15. Select X5 GAIN from the Operating menu.

WFM 90 and WFM 91 Service Manual

5–7

Adjustment Procedures

16. Set the leveled sine wave generator frequency to 50 kHz, and adjust the
generator amplitude for exactly 100 IRE (700 mV PAL) of display.

17. Adjust the peak-to-peak detector Plus amplifier and input control fully
counterclockwise.

18. Note the digital multimeter readout level or the oscilloscope dc level.

19. Set the sine wave generator frequency to 3.58 MHz (4.43 MHz PAL).

20. Adjust the amplitude of the sine wave generator so that the digital multime-

ter readout, or oscilloscope level, matches that noted in step 18.

21. Select X5 FREQ from the Calibration menu, and then select CAL.

22. Adjust the Arrow Buttons for a display amplitude of exactly 100 IRE

(700 mV PAL).

23. Select CAL MENU, and then select SAVE.

24. Select X1 GAIN from the Operating menu, and INT REF from the

Configuration menu.

Vector Quadrature Phase

Perform the following steps to adjust the vector quadrature phase:

1. Replace the signal on the VIDEO IN connector with a 75% color bar signal
from the television signal generator using a 75 W in-line terminator.

2. Select VECTOR display mode.

3. WFM 91 ONLY — Select ALT ON from the Configuration menu.

4. Select QUAD PH from the Calibration menu, select CAL, and then select
RY OFFSET.

5. Adjust the Arrow Buttons for the best center dot overlay.

6. Select QUAD PH.

7. Adjust the Arrow Buttons for the best circle overlay.

8. Select CAL MENU, and then select SAVE.

9. WFM 91 ONLY — Select ALT OFF from the Configuration menu.

5–8

WFM 90 and WFM 91 Service Manual

Adjustment Procedures

Vector Gain and X5 Gain

Phase

Perform the following steps to adjust the vector gain and X5 gain phase:

a. WFM 90 ONLY — Verify that the television signal generator has setup

turned on.

b. Select VEC GAIN from the Calibration menu, select CAL, and then

select TEST ON.

c. Adjust the

Y and B buttons so that the vector dots land in the center of

the red and cyan graticule target boxes. See Figure 5–1.

d. Adjust the

A and " buttons so that the vector dots land in the center of

the yellow and blue graticule target boxes. See Figure 5–1.

Blue

Yellow

Blue

Cyan

Figure 5–1: NTSC graticule showing the vector gain adjustment

e. Select CAL MENU, and then select SAVE.
f. Select X5 PHASE from the Calibration menu, and then select CAL.
g. Select PHASE then use the Arrow Buttons to position the burst vector

exactly on the 180_ graticule line.

h. Select X5 GAIN, and then select X5 PHASE.
i. Adjust the Arrow Buttons so that the burst vector lands exactly on the

180_ graticule line.

j. Select CAL MENU, and then select SAVE.

WFM 90 and WFM 91 Service Manual

5–9

Adjustment Procedures

Audio Gain

Perform the following steps to adjust the audio gain:

1. Connect the output from the audio generator to the AUDIO IN connector.

2. Set the audio generator for a 1 kHz tone output with an amplitude of

+8.0 dBu. Select Signal On from the audio generator.

3. Select the AUDIO display mode on the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor.

4. Select 8 dBu from the Operating menu.

5. Select AUD GAIN from the Calibration menu, and then select CAL.

6. Adjust the Arrow Buttons so that the signal display lands exactly on the

8 dBu graticule lines.

7. Select CAL MENU, and then select SAVE.

5–10

WFM 90 and WFM 91 Service Manual

Maintenance

Maintenance

This section contains instructions for servicing the WFM 90 or WFM 91
Handheld Waveform, Vector, Picture, and Audio Monitor that include the
following information:

H Preparation procedures to observe before performing maintenance
H Procedures for inspecting and cleaning the instrument
H Module removal and replacement instructions
H Troubleshooting procedures
H After-repair adjustments to the instrument
H Repackaging instructions to prepare the instrument for shipment

If the instrument does not function properly, troubleshooting and corrective
measures should be taken immediately to prevent additional problems.

NOTE. Contact your local Tektronix representative for information on where to
return your instrument if it requires repair during the warranty period.

Preparation

Please read and follow these preparation instructions before attempting to
perform any maintenance or service to the instrument.

Servicing Prerequisites

WFM 90 and WFM 91 Service Manual

Make sure of the following before beginning any instrument service:
H The maintenance or service of this instrument must be performed by

qualified service personnel only.

H Read the Service Safety Summary located at the beginning of this manual

before attempting to perform any maintenance or service to the instrument.

H Read the Operating Information section of this manual before attempting to

perform any maintenance or service to the instrument.

6–1

Maintenance

Electrostatic Damage

Prevention

This instrument contains electrical components that are susceptible to damage
from electrostatic discharge. Static voltages of 1 kV to 30 kV are common in
unprotected environments.

CAUTION. Static discharge can damage any semiconductor component in this
instrument.

Observe the following precautions to avoid static damage:

H Minimize handling of static-sensitive components.
H Transport and store static-sensitive components or assemblies in their

original containers, on a metal rail, or on conductive foam. Label any
package that contains static-sensitive assemblies or components.

H Discharge the static voltage from your body by wearing a wrist strap while

handling these components. Servicing static-sensitive assemblies or
components should only be performed at a static-free workstation by
qualified personnel.

H Nothing capable of generating or holding a static charge should be allowed

on the workstation surface.

H Keep the component leads shorted together whenever possible.
H Pick up components by the body, never by the leads.
H Do not slide the components over any surface.
H Avoid handling components in areas that have a floor or work surface

covering capable of generating a static charge.

H Use a soldering iron that is connected to earth ground.
H Use only special antistatic, suction-type or wick-type desoldering tools.

NOTE. A 2% RMA flux content solder is recommended for making repairs in this
instrument. Cleaning of rosin residue is not recommended. Most cleaning
solvents tend to reactivate the rosin and spread it under components where it
may cause corrosion under humid conditions. The rosin residue, if left alone,
does not exhibit these corrosive properties.

6–2

WFM 90 and WFM 91 Service Manual

Inspection and Cleaning

Maintenance

Preventive maintenance consists of cleaning, visual inspection, performance
checking, and, if needed, readjustment. The preventive maintenance schedule
established for the instrument should be based on the environment in which it is
operated and the amount of use. Under average conditions, scheduled preventive
maintenance should be performed every 2000 hours of operation.

General Care

Cleaning

Protect this instrument from adverse weather conditions. The instrument is not
waterproof.

Do not expose the LCD display to direct sunlight for long periods of time.

CAUTION. To avoid damage to this instrument, do not expose it to sprays,
liquids, or solvents.

The instrument should be cleaned often enough to prevent dust or dirt from
accumulating. Dirt acts as a thermal insulating blanket that prevents effective
heat dissipation, and can provide high-resistance electrical leakage paths between
conductors or components in a humid environment.

Clean the exterior of the instrument by removing dust with a lint-free cloth. Use
care to avoid scratching the clear plastic display lens. A small soft-bristled brush
is useful to remove dust from around the selector buttons and connectors.

For further cleaning, use a soft cloth or paper towel dampened with water. You
can use a 75% isopropyl alcohol solution for more efficient cleaning.

CAUTION. To avoid damage to the surface of this instrument, do not use abrasive
or chemical cleaning agents.

If you must clean the interior of the instrument, allow the interior to thoroughly
dry before reassembling and applying power to the instrument.

Display Screen. The display screen is susceptible to smudging from dirt and
grease. The recommended cleaning agent is petroleum ether, which is available
from the vendor listed below:

JT Baker Inc.
Phillipsburg, NJ 08865 USA
(908) 859–2151

WFM 90 and WFM 91 Service Manual

6–3

Maintenance

Visual Inspection

Performance Verification

and Readjustments

After cleaning, carefully check the instrument for defective connections,
damaged parts, and improperly seated transistors or integrated circuits. The
remedy for most visible defects is obvious; however, if heat-damaged parts are
discovered, determine the cause of overheating before replacing the damaged
part.

Periodic checks of the transistors and integrated circuits are not recommended.
The best measure of performance is the actual operation of the component in the
circuit.

Instrument performance should be checked after each 2000 hours of operation or
every 12 months. This will help to ensure maximum performance and assist in
locating defects that may not be apparent during regular operation. Performance
Verification and Adjustment Procedures are included in this manual.

After Repair Adjustments

It is recommended that you perform the Adjustment Procedures starting on
page 5–1 whenever you have removed the Top or Bottom cover during the
service of this instrument.

Repackaging Instructions

Use the following instructions to prepare your instrument for shipment to a
Tektronix, Inc., Service Center:

1. Attach a tag to the instrument showing: the owner, complete address and

2. Package the instrument in the original packaging materials. If the original

3. Seal the carton with shipping tape, industrial stapler, or both.

phone number of someone at your firm who can be contacted, the instrument
serial number, and a description of the required service.

packaging materials are not available, follow these directions:
a. Obtain a carton of corrugated cardboard having inside dimensions six or

more inches greater than the dimensions of the instrument. Use a
shipping carton that has a test strength of at least 250 pounds (113.5 kg).

b. Place the instrument in its carrying pouch or surround the instrument

with a protective bag.

c. Pack dunnage or urethane foam between the instrument and the carton. If

using Styrofoam kernels, overfill the box and compress the kernels by
closing the lid. There should be three inches of tightly packed cushion­ing on all sides of the instrument.

6–4

WFM 90 and WFM 91 Service Manual

Removal and Replacement

This section contains the instructions on how you can remove and replace the
customer replaceable modules and parts of the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor.

CAUTION. To prevent damage to the instrument, disconnect the power adapter
and remove installed batteries from the monitor before starting disassembly. See
Batteries on page 6–21.

To prevent damage to the instrument, be sure to follow the preparation instruc­tions on page 6–2.

Tools Required

Use the tools in Table 6–1 to disassemble the instrument to its individual
modules. Some of these tools are required only for removal of specific instru­ment components.

T able 6–1: Tools required for module removal

Name Description

Torx screwdriver handle Accepts T orx-driver bits
T-10 Torx tip Torx-driver bit for T-10 size screw heads
#1 point Philips tip
9/16” hexagonal driver Deep socket
1/4” hexagonal driver
Flat blade screwdriver
Tweezers or needle-nose pliers
Cleaners See Cleaning on page 6–3
Soldering iron 40 W
Solder 2% RMA flux content solder

WFM 90 and WFM 91 Service Manual

6–5

Removal and Replacement

Procedures

Table 6–2 lists the removal and replacement procedures in this section and their
starting page numbers.

T able 6–2: Removal and replacement procedure list

Replaceable part Page number

Top cover 6–7
LCD display lens 6–8
LCD display 6–9
LCD display padding 6–11
Backlight 6–12
Top board 6–13
Keypad 6–13
Top board shield 6–14
Bottom board 6–16
Backlight board 6–17
Input board assembly 6–18
Battery cover 6–18
Carrying strap 6–19
Turnlock stud and bushing 6–20
Battery cushion pad 6–21
NiCad battery pack 6–21
Alkaline batteries 6–22
Bottom cover 6–23
Battery power connector 6–24
Battery contacts 6–24
Turnlock stud receptacle 6–26
Bottom cover electrical shield 6–27
Battery orientation marker and battery cushion pad 6–27
AC adapter EMI suppressor 6–29

6–6

WFM 90 and WFM 91 Service Manual

Removal and Replacement

Top Cover Assembly

The top cover assembly contains replaceable subparts. Procedures for removing
the subparts are included below.

T op Cover. To remove the top cover assembly, perform the following procedure:

1. Remove the six retaining screws using the Torx-tip screwdriver. See

Figure 6–1.

Figure 6–1: Removing the top cover

WFM 90 and WFM 91 Service Manual

Remove Torx screws (6)

6–7

Removal and Replacement

2. Gently lift the top cover off of the bottom cover.

NOTE. When you are disassembling the WFM 90 or WFM 91, do not let dust
accumulate inside of the top cover. Set the top cover face up on your work
surface or cover it with a lint-free cloth to prevent dust from accumulating on the
inside surface of the cover.

To replace the top cover assembly, perform the following procedure:

1. Make sure that the battery and backlight wires are positioned so that they
will not be pinched between the top and bottom covers.

2. Align the top cover over the bottom cover so that the keypad buttons will
slide through the top cover keypad holes.

3. Gently lower the top cover onto the bottom cover. A slight shaking motion
of the top cover may be necessary to help the keypad buttons slide through
the top cover holes.

LCD Display Assembly

4. Install the six retaining screws using the Torx-tip screwdriver.

LCD Display Lens. To remove the LCD display lens, perform the following
procedure:

1. Remove the top cover. Refer to Top Cover on page 6–7.

2. Press firmly on the LCD display lens from the front of the top cover until it

comes loose from the top cover.

3. Clean any remaining glue residue from the top cover. Refer to Cleaning on
page 6–3.

To replace the LCD display lens, perform the following procedure:

1. Remove the protective cover from the cushion on the new LCD display lens.

2. Align the LCD display lens with the depression in the backside of the top

cover and press the lens into place.

3. Install the top cover. Refer to Top Cover on page 6–7.

The LCD display assembly contains replaceable subparts. Procedures for
removing the subparts are included below.

6–8

CAUTION. To avoid damaging the LCD display, do not touch the face of the
display because it is hard to clean and is easily scratched.

WFM 90 and WFM 91 Service Manual

Removal and Replacement

LCD Display . To remove the LCD display assembly, perform the following
procedure:

1. Remove the top cover. Refer to Top Cover on page 6–7.

2. Disconnect the wires from the two backlight connectors.

3. Grasp the sides of the LCD display to lift it up off of the locating feet and

disconnect the ribbon cable from the back of the display module.

NOTE. The cable connecting the display module to the Bottom board is a zero
insertion-force ribbon cable. To remove the cable from the connector housing,
pull out the connector latch, and then pull the ribbon cable out of the connector.
See Figure 6–2.

Contacts

Open slide
latch connector
to install cable.

Close latch connector

Figure 6–2: Installing the LCD display cable

Contacts

WFM 90 and WFM 91 Service Manual

6–9

Removal and Replacement

NOTE. Some early instruments used cushion pads instead of locating feet to hold
the display module in position. If your instrument has cushion pads, replace the
pads at this time with locating feet. Contact your local Tektronix representative
to order the necessary parts.

To replace the LCD display module, perform the following procedure:

CAUTION. To avoid miscalibrating your display module, do not touch the display
adjustments on the backside of the display module. These adjustments are set by
the manufacturer and should not be adjusted.

1. If you have replaced the display module with a new one, attach the cushion
padding around the display module. Refer to Display Padding on page 6–11.

2. Connect the ribbon cable from the Bottom board into the back of the display
module.

NOTE. The cable connecting the display module to the Bottom board is a zero
insertion-force ribbon cable. To install the cable into the connector, pull out the
connector latch and then push the ribbon cable into the connector housing.
When the cable rests against the back of the connector, press in the connector
latch to lock the cable in place. See Figure 6–2.

3. If you are replacing the ribbon cable, set the LCD display just above its
resting position on the locating feet. Use your finger to crease the ribbon
cable so that when the LCD display is set down on the locating feet, the
ribbon cable does not raise the LCD display up off of the locating feet.

4. Set the LCD display module onto the four locating feet. The locating feet fit
into small holes in each of the four corners on the back of the LCD display.
See Figure 6–3.

5. Connect the backlight wires to the connectors on the side of the display
module.

6. If you have replaced the display module with a new one, carefully remove
the protective plastic cover from the face of the LCD display by prying up
the corner of the cover and pulling it off of the display.

7. If necessary, clean the front of the LCD display. Refer to Cleaning on
page 6–3.

6–10

8. Install the top cover. Refer to Top Cover on page 6–7.

WFM 90 and WFM 91 Service Manual

Short pad

Long pad

Standoff post inserts

into LCD display case.

Removal and Replacement

Level the pad flush

with display case.

LCD locator feet (4)

Figure 6–3: Installing the LCD display

LCD Display Padding. To remove the LCD display padding, perform the

following procedure:

1. Remove the top cover. Refer to Top Cover on page 6–7.

2. Remove the LCD display module. Refer to LCD Display on page 6–9.

WFM 90 and WFM 91 Service Manual

6–11

Removal and Replacement

3. Remove the display padding from the side of the LCD display module.

4. Clean any remaining glue residue from the side of the LCD display module.

Refer to Cleaning on page 6–3.

To replace the LCD display padding, perform the following procedure:

1. Peel the protective cover from the LCD display padding.

2. Align the padding with the top surface of the LCD display module and press

the padding onto the side of the display. See Figure 6–3.

3. Install the LCD display module. Refer to LCD Display on page 6–9.

4. Install the top cover. Refer to Top Cover on page 6–7.

Backlight. To remove the backlight from the LCD display module, perform the
following procedure:

1. Remove the top cover. Refer to Top Cover on page 6–7.

2. Remove the LCD display module. Refer to LCD Display on page 6–9.

3. Remove the display padding from the side of the LCD display module where

the backlight is installed.

4. Remove the two outside retaining screws on the backlight assembly with the
Philips screwdriver. Do not remove the center screw.

5. Gently pull the backlight out of the LCD display module.

To replace the backlight, perform the following procedure:

1. Install the backlight assembly into the side of the LCD display module.

CAUTION. To avoid breaking the backlight, do not force the backlight assembly
into the LCD display module.

2. Install the two retaining screws into the backlight assembly.

3. Install the display padding onto the side of the LCD display module. Refer

to LCD Display Padding on page 6–11. A new display pad is supplied with
the replacement backlight assembly.

4. Install the LCD display module. Refer to LCD Display on page 6–9.

6–12

5. Install the top cover. Refer to Top Cover on page 6–7.

WFM 90 and WFM 91 Service Manual

Removal and Replacement

Top Board Assembly

The Top board assembly contains replaceable subparts. Procedures for removing
the subparts are included below.

T op Board. To remove the Top board, perform the following procedure:

1. Remove the top cover. Refer to Top Cover on page 6–7.

2. Remove the two retaining screws from the top of the Top board.

3. Gently pull on the bottom of Top board to separate it from the Bottom board.

4. If you are replacing the Top board, remove the keypad from the Top board.

Refer to Keypad on page 6–13.

To replace the Top board, perform the following procedure:

1. Install the keypad if you have replaced the Top board. Refer to Keypad on

page 6–13.

2. Gently press on the bottom of the Top board to insert the Top board

connector into the Bottom board connector.

3. Be sure that the circuit board shield is properly aligned. Refer to Top Board

Shield on page 6–14.

4. Install the two retaining screws into the top of the Top board.

5. Install the top cover. Refer to Top Cover on page 6–7.

Keypad. To remove the keypad, perform the following procedure:

1. Remove the top cover. Refer to Top Cover on page 6–7.

2. Remove the Top board. Refer to Top Board on page 6–13.

3. Gently pull the keypad from the Top board.

To replace the keypad, perform the following procedure:

1. Press the nubs on the keypad through the holes in the Top board.

2. Use tweezers or needle-nose pliers from the backside of the Top board to

pull the nubs of the keypad through the Top board. See Figure 6–4.

WFM 90 and WFM 91 Service Manual

6–13

Removal and Replacement

Keypad

Pull nub

through board

with tweezers

Top board

Figure 6–4: Installing the keypad

3. Install the Top board. Refer to Top Board on page 6–13.

4. Install the top cover. Refer to Top Cover on page 6–7.

T op Board Shield. To remove the Top board shield, perform the following
procedure:

1. Remove the top cover. Refer to Top Cover on page 6–7.

2. Remove the two retaining screws from the top of the Top board.

3. Slide the Top board shield out from under the Top board.

To replace the Top board shield, perform the following procedure:

1. If you are replacing the Top board shield, bend the tab on the shield as
shown in Figure 6–5.

6–14

WFM 90 and WFM 91 Service Manual