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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ii

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

iii

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

iv

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

v

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.

xvi

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