Tektronix Stereo System Wfm90 Users Manual

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2015-02-03

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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 © Tektronix, Inc. All rights reserved.
Tektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes
that in all previously published material. Specifications and price change privileges reserved.
Printed in the U.S.A.
Tektronix, Inc., P.O. Box 1000, Wilsonville, OR 97070–1000
TEKTRONIX and TEK are registered trademarks of Tektronix, Inc.

WARRANTY
Tektronix warrants that the products that it manufactures and sells will be free from defects in materials and workmanship
for a period of one (1) year from the date of shipment. If a product proves defective during this warranty period, Tektronix,
at its option, either will repair the defective product without charge for parts and labor, or will provide a replacement in
exchange for the defective product.
In order to obtain service under this warranty, Customer must notify Tektronix of the defect before the expiration of the
warranty period and make suitable arrangements for the performance of service. Customer shall be responsible for
packaging and shipping the defective product to the service center designated by Tektronix, with shipping charges prepaid.
Tektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the
Tektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any
other charges for products returned to any other locations.
This warranty shall not apply to any defect, failure or damage caused by improper use or improper or inadequate
maintenance and care. Tektronix shall not be obligated to furnish service under this warranty a) to repair damage resulting
from attempts by personnel other than Tektronix representatives to install, repair or service the product; b) to repair
damage resulting from improper use or connection to incompatible equipment; c) to repair any damage or malfunction
caused by the use of non-Tektronix supplies; or d) to service a product that has been modified or integrated with other
products when the effect of such modification or integration increases the time or difficulty of servicing the product.
THIS WARRANTY IS GIVEN BY TEKTRONIX IN LIEU OF ANY OTHER WARRANTIES, EXPRESS OR
IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TEKTRONIX’ RESPONSIBILITY TO
REPAIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO
THE CUSTOMER FOR BREACH OF THIS WARRANTY. TEKTRONIX AND ITS VENDORS WILL NOT BE
LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES IRRESPECTIVE
OF WHETHER TEKTRONIX OR THE VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH
DAMAGES.

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 Avoid 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 Tektronix representative and provide the information
below. Service Assurance may not be available in locations outside the United States of America.
Name
Company
Address
City, State, Postal code
Country
Phone

VISA or Master Card number and expiration
date or purchase order number
Repair Protection (1,2, or 3 years)
Calibration Services (1,2,3,4, or 5 years)
Instrument model and serial number
Instrument purchase date

Table of Contents
General Safety Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Safety Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii
xi
xiii
xv

Service Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Offerings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Before You Begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xv
xv
xvii

Product Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Characteristics Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–1
1–5

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–1
2–4

Block Diagram Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3–1

Specifications

Operating Information

Theory of Operation
Performance Verification
Summary Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Performance Verification Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4–1
4–2
4–4

Adjustment Procedures
Summary Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adjustment Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5–1
5–2
5–3

Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inspection and Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
After Repair Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repackaging Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6–1
6–3
6–4
6–4

Removal and Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6–5

Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6–5
6–6

Maintenance

Troubleshooting Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6–31

Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Battery-Fault Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Voltage Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6–31
6–32
6–35

WFM 90 and WFM 91 Service Manual

Table of Contents

Fault Symptom Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting Flowcharts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connector Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6–35
6–36
6–50

Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7–1
7–2

Parts Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using the Replaceable Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8–1
8–2

Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9–1

Options

Replaceable Parts List

Diagrams

WFM 90 and WFM 91 Service Manual

Table of Contents

List of Figures
Figure 2–1: Installing the viewing hood . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–2: Installing the desk stand . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–3: Instrument front panel . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–4: Instrument side panels . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 2–5: On-screen readout messages . . . . . . . . . . . . . . . . . . . . . . .

2–2
2–2
2–4
2–7
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 . . . . . . . . . . . . . . . . . . . .
Figure 6–24: Flowchart for untriggered waveform display . . . . . . . .
Figure 6–25: Flowchart for unlocked vector display . . . . . . . . . . . . . .
Figure 6–26: Flowchart for vector display jitter . . . . . . . . . . . . . . . . .
Figure 6–27: Flowchart for distorted vectors . . . . . . . . . . . . . . . . . . . .
Figure 6–28: Flowchart for problems with the instrument controls .
Figure 6–29: Flowchart for bad menus in the picture display . . . . . .
Figure 6–30: Flowchart for dim or blotchy display . . . . . . . . . . . . . . .
Figure 6–31: Flowchart for bad displays except Picture mode . . . . . .
Figure 6–32: Circuit board connector and pin locations . . . . . . . . . . .

6–43
6–44
6–45
6–46
6–46
6–47
6–48
6–49
6–49
6–50

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

8–4

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

9–1

WFM 90 and WFM 91 Service Manual

Table of Contents

List of Tables
Table 1–1: Vertical deflection system . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–2: DC restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–3: Audio mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–4: Horizontal deflection system . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–5: Vector mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–6: Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–7: Physical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–8: Environmental characteristics . . . . . . . . . . . . . . . . . . . . . .
Table 1–9: Power source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 1–10: Safety/EMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–6
1–7
1–7
1–8
1–8
1–10
1–10
1–10
1–11
1–12

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

2–10

Table 4–1: Summary verification procedure . . . . . . . . . . . . . . . . . . . .
Table 4–2: Equipment required for performance verification . . . . . .

4–1
4–2

Table 5–1: Summary adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 5–2: Equipment required for performance verification . . . . . .

5–1
5–2

Table 6–1: Tools required for module removal . . . . . . . . . . . . . . . . . .
Table 6–2: Removal and replacement procedure list . . . . . . . . . . . . .
Table 6–3: Equipment required for troubleshooting . . . . . . . . . . . . .
Table 6–4: Low-voltage power supplies . . . . . . . . . . . . . . . . . . . . . . . .
Table 6–5: Fault symptom table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6–5
6–6
6–31
6–35
6–36

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

8–2

WFM 90 and WFM 91 Service Manual

Table of Contents

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

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.

Battery Recycling

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
Rechargeable Battery Recycling Corp.
P.O. Box 141870
Gainesville, Florida 32614

viii

(800) BATTERY
(800) 227-7379
www.rbrc.com

WFM 90 & WFM 91 Service Manual

General Safety Summary

Symbols and Terms

Terms in this Manual. These terms may appear in this manual:
WARNING. Warning statements identify conditions or practices that could result
in injury or loss of life.

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

Terms on the Product. These terms may appear on the product:
DANGER indicates an injury hazard immediately accessible as you read the
marking.
WARNING indicates an injury hazard not immediately accessible as you read the
marking.
CAUTION indicates a hazard to property including the product.
Symbols on the Product. The following symbols may appear on the product:

DANGER
High Voltage

Certifications and
Compliances

Protective Ground
(Earth) Terminal

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

General Safety Summary

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

Service Safety Summary

xii

WFM 90 & WFM 91 Service Manual

Preface
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.

About This Manual
This manual is composed of the following sections:
H

Specifications lists the electrical and environmental specifications and
provides a general product description.

Operating Information describes installation and front panel operation of the
instrument.

Theory of Operation contains a module-level description based on block
diagrams of the instrument circuitry.

Performance Verification provides procedures for verifying instrument
performance.

Adjustment Procedures provides procedures for adjusting the instrument to
meet performance levels listed in Specifications.

Maintenance contains instructions for cleaning the instrument, procedures
for removal and replacement of instrument modules, and troubleshooting
procedures.

Options lists all of the options that you might find on your instrument.

Replaceable Electrical Parts points you to Replaceable Mechanical Parts
for the list of replaceable electrical parts and assemblies.

Diagrams contains the instrument interconnect diagram.

Replaceable Mechanical Parts lists the part numbers of the replaceable
electrical and mechanical parts and assemblies.

Related Manuals
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
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.

Warranty Repair Service

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

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.

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

Annual maintenance agreements that provide for either calibration and repair
or calibration only of the 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.
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.

Self Service

Tektronix supports repair to the module level by providing Module Exchange
and Module Repair and Return.
Module Exchange. This service reduces down time for repair by 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

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.

Before You Begin
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.

Read the Safety Summary found at the beginning of this manual.

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
This section includes the following information:
H

Product description

Characteristics tables

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

Product Description
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

Menu-assisted monitoring operation

Video and audio signal input and output capability

Waveform, Vector, Picture, Audio, and Waveform-in-Picture (WIP) display
modes

Line Select mode for the selection of any single line of video for display

Time-out mode to shut off power to the display backlight and/or the
instrument when the instrument is not in use

Signal level alarm mode for the waveform and audio displays

Preset menu to store or recall the front panel and menu setup

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.
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.

1–2

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/division), 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.
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.

More Information

1–4

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

Front panel operation is described in the Operating Information section

Instrument options are listed in the Options section

Standard and optional accessories are listed in the Replaceable Mechanical
Parts section

WFM 90 and WFM 91 Service Manual

Specifications

Characteristics Tables
The characteristics tables use the following abbreviations:
Performance Requirement. All performance requirements in the characteristics
tables are identified with Req and can be assured by performing the procedures
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.

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

Table 1–1: Vertical deflection system
Category

Description

Frequency Response

Deflection Factor

REF:
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.

REQ:

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%.

1 V Full Scale: 1 V input displayed within 1% of 140 IRE.
REF:

REQ:

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

REQ:

1–6

Flat filter selected.

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

Maximum Absolute Input Level

Specifications apply for full screen height video input signal with Variable Gain off.

REF:

Specifications apply for full screen height video input signal with Variable 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%.

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.
REF:

$5 VDC plus peak AC.

REF:

Displays in excess of 200 IRE (1.428 V) may cause frequency response aberrations.

WFM 90 and WFM 91 Service Manual

Specifications

Table 1–1: Vertical deflection system (Cont.)
Category

Description

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.

Table 1–2: DC restoration
Category

Description

DC Restorer Clamp Time
Frequency Response at
60 Hz (50 Hz PAL)

REF:
REQ:

Back Porch.

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.

Table 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

Table 1–4: Horizontal deflection system
Category

Description

Sweep

REQ:

Sweep will occur in all horizontal mode settings with or without synchronization.
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.

Integral Linearity

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%.

REQ:

Within 1%.

Horizontal Position

REF:

Measured between the 10 ms and 110 ms points on the 10 ms/division
(2LINE) sweep.

REF:

Any portion of a synchronized video sweep can be positioned on
screen in all sweep modes.

Table 1–5: Vector mode
Category

Description

Chrominance Processing Nominal Subcarrier
Frequency (FSC)
Chrominance Processing Chrominance
Bandwidth

REF:

REQ:

NTSC: 3.579545 MHz.
PAL: 4.43361875 MHz.

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

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

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.

Display Vector Phase Accuracy

REF:

1.25°.

REF:

Measured with color bar signal.

Display Vector Gain Stability

REF:

Typically 2.5%.

Display Quadrature Phasing

REF:

Typically 0.5°.

1–8

WFM 90 and WFM 91 Service Manual

Specifications

Table 1–5: Vector mode (Cont.)
Category

Description

Display Differential Phase

Display Differential Gain

Subcarrier Regenerator Pull-In Range

REQ:

Subcarrier Regenerator Pull-In Time

REF:

1°.

REF:

Measured with 140 IRE (1 V) linearity signal (5 step, 10 step, or Ramp)
with 40 IRE (300 mV) of subcarrier.

REF:

1%.

REF:

Measured with 140 IRE (1 V) linearity signal (5 step, 10 step, or Ramp)
with 40 IRE (300 mV) of subcarrier.

NTSC: 50 Hz of FSC.
PAL: 10 Hz of FSC.
REF:

Subcarrier Regenerator free-runs in absence of appropriate signal.
Reference can be burst of either displayed signal or external reference
signal.

REF:

Pull-In Time: Within 1 second, with subcarrier frequency within 50 Hz
(10 Hz for PAL) of FSC.

Subcarrier Regenerator Phase Shift with
Subcarrier Frequency Change

REQ:

NTSC: 2° from FSC to (FSC + 50 Hz), or FSC to (FSC – 50 Hz).
PAL: 2° from FSC to (FSC + 10 Hz), or FSC to (FSC – 10 Hz).

Subcarrier Regenerator Phase Shift with Burst
Amplitude Change

REQ:

2° from nominal burst amplitude to 6 dB.

Subcarrier Regenerator Phase Shift with Variable
Gain Control

REQ:

REF:

Internal or External burst reference.

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

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

Table 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 synchronize sweeps.

REQ:

DC Input Impedance (unterminated): 15 kW.

External Reference Input

REF:

Return Loss (75 W): 40 dB from 50 kHz to 6 MHz (with 75 W termination on, instrument power on).

REF:

Absolute Maximum Input Voltage: 12 VDC plus peak AC.

Table 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.

Table 1–8: Environmental characteristics
Category

Description

Operating Altitude

REQ:

To 15,000 feet (4572 meters).
REF:

Operating Temperature

REQ:

IEC 1010-1 compliance to 2000 meters.

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:

Pollution Degree

1–10

REQ:

Rated for indoor use only.

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

WFM 90 and WFM 91 Service Manual

Specifications

Table 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.

Table 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:
Waveform Mode:
Vector Mode:

Operating Time

REF:

Alkaline Batteries:
Picture Mode:
Waveform Mode:
Vector Mode:
NiCad Batteries:
Picture Mode:
Waveform Mode:
Vector Mode:

REF:

External Power

REQ:

2.5 hours
2 hours
2 hours
4 hours
3 hours
3 hours

Fully charged or new batteries.

DC Source of 11 V to 18 V.
REF:

WFM 90 and WFM 91 Service Manual

5.5 W
7.2 W
7.2 W

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

1–11

Specifications

Table 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).
UL3111 – 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
EN 50082-1 Immunity:
IEC 801-2
IEC 801-3
IEC 801-4

1–12

Class B Radiated and Conducted Emissions
Electrostatic Discharge Immunity
RF Electromagnetic Field Immunity
Electrical Fast Transient/Burst Immunity

WFM 90 and WFM 91 Service Manual

Operating Information

Operating Information
This section contains the following information:
H

Mechanical and electrical installation instructions

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

ÏÏÏÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏÏÏÏ
ÏÏÏÏÏÏÏÏÏÏÏÏ
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.

Figure 2–2: Installing the desk stand

2–2

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.

Figure 2–3: Instrument front panel

2–4

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.

Press the VECT button to enter the Vector display mode.

Press the AUDIO button to enter the Audio display mode.

Press the PIX button to enter the Picture display mode.

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.

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.

Press the LINE SEL button to toggle the Line Select mode on and off and to
display the Line Select menu.

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

Operating Information

DC IN 11-18V

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.
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.

2–8

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.
1
GAIN UNCAL
SYNC

MISSING
100

EXT REF

10uS/DIV
V1.1

LOW BAT

80
60
40
20
0
–20
–40

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.

The EXT REF message appears in the Waveform and Vector display modes
when the video signal is locking to an external video reference signal.

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

Default Settings

The instrument software version number is displayed when the Configuration menu is open with the DISPLAY category selected.

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.

The MISSING SYNC message appears in all video display modes when the
signal reference has been lost.

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

2–10

Instrument Parameter

Factory Default Setting

Display mode

Waveform

Signal reference

Internal

Filter

Flat

DC restorer speed

Slow

Gain

Variable gain

Off

Sweep

2H (2 Line)

Mag

Off

Bars

75%

Setup (WFM 90 only)

Yes

Alt Phase (WFM 91 only)

Off

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

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.

Top 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

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.

WFM 90 and WFM 91 Service Manual

3–1

Theory of Operation

Backlight Power Supply
Board

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.

LCD Display and
Backlight

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

Input Board

Bottom Board

P/O Top Board
Clamp

Video
Out

Front
Panel
Keys

LPF

Video
In

Vert
Defl

Video In

Ext
Ref

Video
Out

Ref

Audio
In

Rasterizer
and
Graphics

Horiz
Defl

RGB from
Rasterizer
and Graphics

RGB

Audio

Var
Gain

Part of
mP

Instrument
Control

R–Y
Headphone

DC In
11–18 VDC
Battery

Fuse
Burst
Lock

Fuse

Power Supply
and Battery
Charger

Fsc

Vectorscope
(Including Ø
shifter)
B–Y

±8 VDC
+5 VDC
Vector
±8 VDC
+5 VDC

NTSC (or PAL)
Decoder (Self
contained
subcarrier
regenerator)

Sweep

Trig

DSync

RGB

Sel Vid

LCD Display
and Backlight

P/O Top Board
Control DAC
(16 analog
Outputs)

Subcarrier
Oscillator

Sync
Separator

Timing

Part of
mP

Display
Brightness
and View
Adjust

Timing
2

Backlight
Power
Supply
Board
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

List of equipment required to perform the procedures

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.
Table 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.

4–5

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%.

4–6

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.

4–7

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.

4–7

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.

4–8

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%.

4–9

WFM 90 and WFM 91 Service Manual

4–1

Performance Verification

Table 4–1: Summary verification procedure (Cont.)
Procedure

Procedure Requirement

Page #

Vector phase stability

Phase Shift with Subcarrier Frequency Change from FSC to FSC 50 Hz
(FSC 10 Hz PAL): 2°. Phase Shift with Burst Amplitude Change from
Nominal to 6 dB: 2°. Phase Shift with Variable Gain Control Varied
from +3 dB to –6 dB: 1°.

4–11

Chrominance bandwidth

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

4–11

Audio gain and frequency response

Measurement Accuracy: 0.5 dB at 1 kHz. Frequency Response: 0.5 dB
from 50 Hz to 20 kHz.

4–13

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

Audio Flatness: 2.5:1

Table 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

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

Leveled sine wave generator

Output Level Range: –11.55 dBm (200 mV) to
0.43 dBm (800 mV);
Frequency: 50 kHz to 10 MHz

Tektronix SG 5032 Leveled Sine Wave Generator

Function generator

Range: 0.1 to 5 Vpp when loaded by 75 W,
10 Vpp when unloaded;
Frequency: 50 kHz to 10 MHz.

Tektronix FG 5032 Function Generator

Audio generator

Amplitude Range: –10 dBu to 8 dBu;
Frequency: 1 kHz to 50 kHz

Tektronix ASG 100 Audio Signal Generator

Voltmeter

Range: 0 VDC to 100 VDC;
Accuracy: 0.1%

Tektronix DM 504A2 Digital Multimeter

4–2

WFM 90 and WFM 91 Service Manual

Performance Verification

Table 4–2: Equipment required for performance verification (Cont.)
Equipment Description

Minimum Requirements

Equipment Example

Frequency counter

Range: 10 Hz to 10 MHz;
Accuracy: 0.001%

Tektronix DC 503A2 Universal Counter

Video amplitude calibrator
(VAC)

Signal: Adjustable square wave 0.0 mVpp to
999.9 mVpp; Resolution: 0.1 mV; Accuracy:
0.05%; Frequency: Approximately 270 Hz

Tektronix part number 067-0916-002

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
connectors

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

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

Tektronix part number 067-0525-02

BNC female to BNC female
connector

Tektronix part number 103-0028-00

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.

Requires a Tektronix TM 500-Series or TM 5000-Series Power Module Mainframe.

WFM 90 and WFM 91 Service Manual

4–3

Performance Verification

Performance Verification 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

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 requirement.
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 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

4–4

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.

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

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.

Sync Separation

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).
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.

Variable Gain Range and
Vertical Position Range

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.
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.

Overscan

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

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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.
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 Waveform, Vector, Picture, and Audio Monitor.

4–10

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 FSC to FSC 50 Hz
(FSC 10 Hz PAL): 2°. Phase Shift with Burst Amplitude Change from
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.
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.

Chrominance Bandwidth

This procedure verifies the following requirement:
Chrominance Bandwidth: Upper –3 dB Point: FSC + 500 kHz, 100 kHz.
Lower –3 dB Point: FSC – 500 kHz, 100 kHz.
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 minimumloss 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.
–3 dB Points

Compass rose

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

List of equipment required to perform the procedures

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.
Table 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.
Table 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

NTSC: Tektronix TSG 100;
PAL: Tektronix TSG 111

Leveled sine wave generator

Output Level Range: –11.55 dBm (200 mV) to
0.43 dBm (800 mV);
Frequency: 50 kHz to 10 MHz

Tektronix SG 5031 Leveled Sine Wave Generator

Function generator

Range: 0.1 to 5 Vpp when loaded by 75 W,
10 Vpp when unloaded;
Frequency: 50 kHz to 10 MHz.

Tektronix FG 5031 Function Generator

Audio generator

Amplitude Range: –10 dBu to 8 dBu;
Frequency: 1 kHz to 50 kHz

Tektronix ASG 100 Audio Signal Generator

Voltmeter

Range: 0 VDC to 100 VDC;
Accuracy: 0.1%

Tektronix DM 504A1 Digital Multimeter

Frequency counter

Range: 10 Hz to 10 MHz;
Accuracy: 0.001%

Tektronix DC 503A1 Universal Counter

Video amplitude calibrator
(VAC)

Signal: Adjustable square wave 0.0 mVpp to
999.9 mVpp; Resolution: 0.1 mV; Accuracy:
0.05%; Frequency: Approximately 270 Hz

Tektronix part number 067-0916-001

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)1

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
connectors

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

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

Tektronix part number 067-0525-02

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

BNC female to BNC female
connector

Tektronix part number 103-0028-00

BNC female to dual banana
adapter

Tektronix part number 103-0090-00

5–2

Requires a Tektronix TM 500-Series or TM 5000-Series Power Module Mainframe.

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

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

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.

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.

WFM 90 and WFM 91 Service Manual

5–3

Adjustment Procedures

Adjustment Methodology

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.

Preliminary Setup

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

Raster VCO

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.
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.

5–6

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 multimeter 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 multimeter 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.

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

Procedures for inspecting and cleaning the instrument

Module removal and replacement instructions

Troubleshooting procedures

After-repair adjustments to the instrument

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

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.

Read the Service Safety Summary located at the beginning of this manual
before attempting to perform any maintenance or service to the instrument.

Read the Operating Information section of this manual before attempting to
perform any maintenance or service to the instrument.

WFM 90 and WFM 91 Service Manual

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.

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.

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.

Nothing capable of generating or holding a static charge should be allowed
on the workstation surface.

Keep the component leads shorted together whenever possible.

Pick up components by the body, never by the leads.

Do not slide the components over any surface.

Avoid handling components in areas that have a floor or work surface
covering capable of generating a static charge.

Use a soldering iron that is connected to earth ground.

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

Maintenance

Inspection and Cleaning
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

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.

Cleaning

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

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.

Performance Verification
and Readjustments

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
phone number of someone at your firm who can be contacted, the instrument
serial number, and a description of the required service.
2. Package the instrument in the original packaging materials. If the original
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.
3. Seal the carton with shipping tape, industrial stapler, or both.

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

Description

Torx screwdriver handle

Accepts Torx-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

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Removal and Replacement

Procedures
Table 6–2 lists the removal and replacement procedures in this section and their
starting page numbers.
Table 6–2: Removal and replacement procedure list

6–6

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

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Removal and Replacement

Top Cover Assembly

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

Remove Torx screws (6)

Figure 6–1: Removing the top cover

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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.
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.

LCD Display Assembly

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

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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

Close latch connector

Open slide
latch connector
to install cable.
Contacts

Figure 6–2: Installing the LCD display cable

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

6–10

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Removal and Replacement

Level the pad flush
with display case.

Short pad
Long pad

Standoff post inserts
into LCD 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.

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

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Removal and Replacement

Top Board Assembly

The Top board assembly contains replaceable subparts. Procedures for removing
the subparts are included below.
Top 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

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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.
Top 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

Removal and Replacement

Lift up the board to slip the
shield underneath the top board.

The shield tab goes on
top of the board post
and under the circuit
board.

Shield

Fold tab

Figure 6–5: Installing the Top board shield
2. Slide the shield under the Top board and align the cutouts in the shield with
the mounting posts of the Top board.
NOTE. Be sure to properly align the tab of the Top board shield so that the tab is
under the Top board and that the Top board retaining screw goes through the
tab. Failure to do this will result in noisy display graphics. See Figure 6–5.
3. Install the two retaining screws into the top of the Top board.
4. Install the top cover. Refer to Top Cover on page 6–7.

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Removal and Replacement

Bottom Board

To remove the Bottom board, 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 Top board. Refer to Top Board on page 6–13.
4. Remove the battery cover. Refer to Battery Cover on page 6–18.
5. Lift on the Bottom board while you press on the battery connector in the
battery compartment.
6. Gently pull the Backlight board from the back of the Bottom board.
7. Gently pull the Input board assembly from the back of the Bottom board.
To replace the Bottom board, perform the following procedure:
1. Install the Input board into the back of the Bottom board.
2. Install the Backlight board into the back of the Bottom board.
3. Align the Backlight and Input boards with the slots in the bottom cover and
gently slide the boards into the bottom cover. See Figure 6–6.
4. Install the Top board. Refer to Top Board on page 6–13.
5. Install the LCD display module. Refer to LCD Display on page 6–9.
6. Install the top cover. Refer to Top Cover on page 6–7.
7. Install the battery cover. Refer to Battery Cover on page 6–18.

6–16

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Removal and Replacement

Backlight
board
Align the Backlight and
Input boards into the
slots of the bottom cover

Input board
assembly

Figure 6–6: Installing the Bottom board

Backlight Board

To remove the Backlight board, perform the following procedure:
1. Remove the top cover. Refer to Top Cover on page 6–7.
2. Remove the battery cover. Refer to Battery Cover on page 6–18.
3. Lift on the Bottom board while pressing on the battery connector in the
battery compartment.
4. Gently pull the Backlight board from the back of the Bottom board.
To replace the Backlight board, perform the following procedure:
1. Be sure that the Backlight board shield is in place if you have replaced the
Backlight board.
2. Install the Backlight board into the back of the Bottom board.
3. Align the Backlight and Input boards with the slots in the bottom cover and
gently slide the boards into the bottom cover.

WFM 90 and WFM 91 Service Manual

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Removal and Replacement

4. Install the Top board. Refer to Top Board on page 6–13.
5. Install the LCD display module. Refer to LCD Display on page 6–9.
6. Install the top cover. Refer to Top Cover on page 6–7.
7. Install the battery cover. Refer to Battery Cover on page 6–18.

Input Board Assembly

To remove the Input board, perform the following procedure:
1. Remove the top cover. Refer to Top Cover on page 6–7.
2. Remove the battery cover. Refer to Battery Cover on page 6–18.
3. Lift on the Bottom board while you press on the battery connector in the
battery compartment.
4. Gently pull the Input board assembly from the back of the Bottom board.
5. Unscrew the retaining nuts from the three BNC connectors on the rear panel.
6. Pull the rear panel cover off of the BNC connectors.
To replace the Input board, perform the following procedure:
1. Install the rear panel cover over the BNC connectors on the Input board.
2. Install the retaining nuts onto the three BNC connectors on the rear panel.
3. Install the Input board assembly onto the back of the Bottom board.
4. Align the Backlight and Input boards with the slots in the bottom cover and
gently slide the boards into the bottom cover.
5. Install the top cover. Refer to Top Cover on page 6–7.
6. Install the battery cover. Refer to Battery Cover on page 6–18.

Battery Cover Assembly

The battery cover assembly contains replaceable subparts. Procedures for
removing the subparts are included below.
Battery Cover. To remove the battery cover assembly, perform the following
procedure:
1. Turn the turnlock stud 1/4-turn counterclockwise.
2. Pull outwards on the upper portion of the battery cover.

6–18

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Removal and Replacement

To replace the battery cover assembly, perform the following procedure:
1. Place the lower lip of the battery cover into the instrument housing and press
the top portion of the cover into the instrument. See Figure 6–7.
Battery Cover

Figure 6–7: Installing the battery cover
2. Secure the battery cover by turning the turnlock stud 1/4-turn clockwise.
Carrying Strap. To remove the carrying strap, perform the following procedure:
1. Remove the battery cover. Refer to Battery Cover on page 6–18.
2. To remove the carrying strap, remove the two retaining nuts on the inside of
the battery cover and pull the carrying strap off of the cover.

WFM 90 and WFM 91 Service Manual

6–19

Removal and Replacement

To replace the carrying strap, perform the following procedure:
1. Insert the two standoff studs of the carrying strap through the battery cover
and install the two retaining nuts.
2. Install the battery cover. Refer to Battery Cover on page 6–18.
Turnlock Stud and Bushing. To remove the turnlock stud and bushing, perform
the following procedure:
1. Remove the battery cover. Refer to Battery Cover on page 6–18.
2. Gently pry up on the outside portion of the bushing as shown in Figure 6–8.
3. Gently pull and rock the turnlock stud while holding the bushing.
Battery Cover

Bushing

Turnlock

Bushing

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

6–20

WFM 90 and WFM 91 Service Manual

Removal and Replacement

To replace the turnlock stud and bushing, perform the following procedure:
1. Press the turnlock stud into the bushing.
2. To install the turnlock stud and bushing into the battery cover, press firmly
on the turnlock stud head. Be sure to keep the bushing head level with the
battery cover while you press on the turnlock stud. The bushing will snap
into place when it is correctly installed.
3. Install the battery cover. Refer to Battery Cover on page 6–18.
Battery Cushion Pad. To remove the battery cushion pad, perform the following
procedure:
1. Remove the battery cover. Refer to Battery Cover on page 6–18.
2. To remove the cushion pad, pry it up around the edges and pull it off of the
battery cover.
3. If necessary, clean the surface of the cushion pad to remove any remaining
glue residue. See Cleaning on page 6–3.
To replace the battery cushion pad, perform the following procedure:
1. Peel off the protective covering of the adhesive surface of the cushion pad.
2. Position the cushion pad in place above the battery cover before you press it
onto the battery cover. Rub your fingers over the pad once it is positioned on
the battery cover to make sure the pad is securely in place.
3. Install the battery cover. Refer to Battery Cover on page 6–18.

Batteries

There are two procedures for replacing the batteries. The first is for the optional
NiCad battery pack and second is for alkaline batteries.
NiCad Battery Pack. To remove the NiCad battery pack, perform the following
procedure:
1. Remove the battery cover. Refer to Battery Cover on page 6–18.
2. Grasp the batteries close to the wire leads. Use your thumb to press in on the
top portion of the battery connector tab, and then pull gently upwards. See
Figure 6–9.

WFM 90 and WFM 91 Service Manual

6–21

Removal and Replacement

Grasp wire

Press

Figure 6–9: Removing the NiCad battery pack
To replace the NiCad battery pack, perform the following procedure:
1. Press the battery connector onto the jumper in the battery compartment. Be
sure the battery connector tab snaps onto the jumper housing to prevent a
loss of battery power.
2. Install the battery cover. Refer to Battery Cover on page 6–18.
Alkaline Batteries. To remove the C-size alkaline batteries, perform the following
procedure:
1. Remove the battery cover. Refer to Battery Cover on page 6–18.
2. Carefully pull the batteries out of the battery compartment.

6–22

WFM 90 and WFM 91 Service Manual

Removal and Replacement

To replace the C-size alkaline batteries, perform the following procedure:
1. Press the batteries into place according to the polarity label on the bottom of
the battery compartment. See Figure 6–10.
NOTE. The polarity of the alkaline batteries must be correct for the instrument to
operate. Always replace all of the alkaline batteries at the same time when
replacing discharged batteries.

Figure 6–10: Installed polarity of alkaline batteries
2. Install the battery cover. Refer to Battery Cover on page 6–18.

Bottom Cover Assembly

The bottom cover assembly contains replaceable subparts. Procedures for
removing and installing the subparts are included below.
Bottom Cover. To remove the bottom cover, perform the following procedure:
1. Remove any installed batteries. Refer to Batteries on page 6–21.
2. Remove the six Torx screws from the bottom cover.
3. Carefully remove the bottom cover and place it beside the top cover.
CAUTION. To prevent damage to the battery-power wires soldered to the bottom
cover, carefully remove the bottom cover

WFM 90 and WFM 91 Service Manual

6–23

Removal and Replacement

4. Lift the Bottom board slightly out of the top cover so that you can pull the
battery-power wires from jumper J21 of the Bottom board. See Figure 6–12.
To replace the bottom cover, perform the following procedure:
1. Lift the Bottom board slightly out of the top cover so that you can connect
the battery-power wires onto jumper J21 of the Bottom board.
2. Carefully place the bottom cover onto the top cover.
CAUTION. To prevent damage to the battery-power or backlight wires, carefully
replace the bottom cover. The bottom cover has slots in the molded plastic to
hold both the Backlight board and Input board in place.
3. Install the six Torx screws into the bottom cover.
4. Install your removed batteries. Refer to Batteries on page 6–21.
Battery Power Connector. To remove the battery power connector, perform the
following procedure:
1. Remove the bottom cover. Refer to Bottom Cover on page 6–23.
2. Unsolder the battery connector wires from the battery contacts.
To replace the battery power connector, perform the following procedure:
1. Solder the battery power connector wires to the battery contacts. See
Figure 6–12.
2. Install the bottom cover. Refer to Bottom Cover on page 6–23.
Battery Contacts. To remove the battery contacts, perform the following
procedure:
1. Remove the bottom cover. Refer to Bottom Cover on page 6–23.
2. To remove one of the battery contacts that has the battery power connector
soldered to it, unsolder the battery connector wire before you remove the
battery contact.
3. Pry the battery contact past the retaining lip on the bottom cover. See
Figure 6–11.

6–24

WFM 90 and WFM 91 Service Manual

Removal and Replacement

Retaining lip

Alignment ridge

Battery contacts

Figure 6–11: Battery contact installation alignment
4. Push the battery contact through the slot on the bottom cover.
To replace the battery contacts, perform the following procedure:
1. Align the slot in the battery contact with the battery contact alignment ridge
on the bottom cover. See Figure 6–11.
2. Push the battery contact through the slot in the bottom cover until the battery
contact snaps past the retaining lip of the bottom cover.
3. If you replaced one of the battery contacts that had the battery-power wires
soldered to it, resolder the battery connector wire to the battery contact. See
Figure 6–12.

WFM 90 and WFM 91 Service Manual

6–25

Removal and Replacement

Solder only this side

Depress receptacle
prongs

Black wire

Red wire

Receptacle
prongs

Turnlock stud receptacle

Figure 6–12: Battery power-wire and turnlock stud receptacle installation
4. Install the bottom cover. Refer to Bottom Cover on page 6–23.
Turnlock Stud Receptacle. To remove the turnlock stud receptacle, perform the
following procedure:
1. Remove the bottom cover. Refer to Bottom Cover on page 6–23.
2. Depress the retaining fingers on the turnlock stud receptacle and push the
receptacle through the bottom cover. See Figure 6–12.

6–26

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Removal and Replacement

To replace the turnlock stud receptacle, perform the following procedure:
1. Push the turnlock stud receptacle through the bottom cover. Be sure the
retaining fingers snap into position. See Figure 6–12.
2. Install the bottom cover. Refer to Bottom Cover on page 6–23.
Bottom Cover Electrical Shield. Remove the electrical shield by performing the
following procedure:
1. Remove the bottom cover. Refer to Bottom Cover on page 6–23.
2. Pry up the electrical shield on the inside of the bottom cover around the
edges and peel it off of the bottom cover.
3. If necessary, clean the surface of the bottom cover to remove any remaining
glue residue.
To replace the electrical shield, perform the following procedure:
1. Peel off the protective covering of the adhesive surface of the electrical
shield.
2. Position the electrical shield in place above the inside of the bottom cover
before you press it onto the bottom cover. Be sure to align the hole in the
shield with the hole in the bottom cover.
3. Rub your fingers over the shield once it is positioned on the bottom cover to
make sure the pad is securely in place.
4. Install the bottom cover. Refer to Bottom Cover on page 6–23.
Battery Orientation Marker and Battery Cushion Pad. To remove the battery
orientation marker and/or the battery cushion pad, perform the following
procedure:
1. Remove the battery cover. Refer to Battery Cover on page 6–18.
2. To only remove the battery orientation marker, pry it up around the edges
and peel it off of the battery cushion pad on the bottom cover.
3. To remove both the battery orientation marker and the battery cushion pad,
pry the battery cushion pad up around the edges, and peel it off of the bottom
cover.
4. If necessary, clean the surface of the battery cushion pad or the bottom cover
to remove any remaining glue residue. Refer to Cleaning on page 6–3.

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Removal and Replacement

To replace the battery orientation marker and/or the battery cushion pad, perform
the following procedure:
1. To replace the battery cushion pad and the battery orientation marker, peel
off the protective covering of the adhesive surface of the battery cushion pad.
2. Position the battery cushion pad in place above the bottom cover before you
press it onto the bottom cover. See Figure 6–13.
3. Rub your fingers over the battery cushion pad once it is positioned on the
bottom cover to make sure the pad is securely in place.

Line up holes to aid
positioning

Battery orientation
marker

Battery cushion
pad

Figure 6–13: Battery orientation marker position

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Removal and Replacement

4. Peel off the protective covering of the adhesive surface of the battery
orientation marker.
5. Position the battery orientation marker in place above the battery cushion
pad before you press it onto the battery cushion pad. See Figure 6–13.
6. Rub your fingers over the battery orientation marker once it is positioned on
the battery cushion pad to make sure the marker is securely in place.
7. Install the battery cover. Refer to Battery Cover on page 6–18.

AC Adapter EMI
Suppressor

To remove the AC adapter EMI suppressor, perform the following procedure:
1. Release the retaining latches on the side of the EMI suppressor.
2. Pull the AC adapter cord from the EMI suppressor.
To replace the AC adapter EMI suppressor, perform the following procedure.
1. Place the EMI suppressor within 12 inches of the end of the adapter cord.
NOTE. The EMI suppressor is most effective when placed close to the end of the
AC adapter cord.
2. Loop the AC adapter cord through the middle of the EMI suppressor. Close
the EMI suppressor until the sides of the suppressor latch together. See
Figure 6–14.
EMI suppressor

Loop the cord
through once

Figure 6–14: Installing the EMI suppressor

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Removal and Replacement

6–30

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures
This section contains the following information starting on the listed pages:
H

List of equipment required to perform the procedures, this page

Battery-fault analysis, page 6–32

Low-voltage power supply, page 6–34

Fault symptom table, page 6–35

Troubleshooting flowcharts, page 6–36

Connector pin locator diagram, page 6–50

Equipment Required
The following equipment and accessory items are required to perform the
Troubleshooting Procedures. Minimum requirement specifications are followed
by an example of equipment that meet these specifications.
Table 6–3: Equipment required for troubleshooting
Equipment Description

Minimum Requirements

Equipment Example

Television test signal generator

75% color bar and 100% flat field test signals for
the television standard of the monitor to be
tested

NTSC: Tektronix TSG 100;
PAL: Tektronix TSG 111

Audio generator

Amplitude Range: –10 dBu to 8 dBu;
Frequency: 1 kHz to 50 kHz

Tektronix ASG 100 Audio Signal Generator

Oscilloscope

100 MHz

Tektronix 1465B

Picture monitor

Composite video for the television standard of
the monitor to be tested

75 W coaxial cable

Two cables required, male-to-male BNC
connectors

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

Test resistor

Two 30 W, 3 W

Tektronix part number 308-0142-00

Test resistor

10 kW, 2 W

Tektronix part number 305-0103-00

Jumper wires

Three, 8 inch

20 AWG

Circuit board vise

12 V power supply

WFM 90 and WFM 91 Service Manual

Tektronix PS282

6–31

Troubleshooting Procedures

Battery-Fault Analysis
Use this procedure to troubleshoot battery or battery charging problems when the
instrument functions properly when powered by the AC adapter. If there are no
battery problems or if the instrument does not function properly with the AC
adapter, go to Low-Voltage Power Supply on page 6–35.

WFM 90 SN B011362
and Below;
WFM 91 SN B010470
and Below

Use the following procedure to determine if the battery charger circuit is
operating properly:
NOTE. The battery-charging circuit in the WFM 90 (SN B011362 and below) and
the WFM 91 (SN B010470 and below) will not charge a completely discharged
battery. The battery must have at least +4 V charge across the battery connector
before the charging circuit will operate.
1. Remove the AC adapter from the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and Audio Monitor.
2. Remove the battery cover and any installed batteries from the instrument.
See Batteries on page 6–21.
3. Use three jumper wires to connect two 30 W, 3 W resistors and an external
+12 VDC power supply to the battery connector pins. See Figure 6–15.

Battery connector

Jumper wires (3)
Test resistor #2

+
Test resistor #1

External power supply

+12V

–
Figure 6–15: Testing the battery charging circuit – WFM 90 SN B011362 and below;
WFM 91 SN B010470 and below

6–32

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use the following procedure to determine if the battery charger circuit is
operating properly:
1. Remove the AC adapter from the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and Audio Monitor.
2. Remove the battery cover and any installed batteries from the instrument.
See Batteries on page 6–21.
3. Use three jumper wires to connect a 30 W, 3 W resistor to the battery
connector pins. See Figure 6–16.

Battery connector

Jumper wires (3)

–

+
Test resistor

Figure 6–16: Testing the battery charging circuit – WFM 90 SN B011363 and above;
WFM 91 SN B010471 and above

WFM 90 and WFM 91 Service Manual

6–33

Troubleshooting Procedures

NOTE. If the jumper wires will not stay securely attached to the battery connector
pins, you will need to remove the instrument bottom case to obtain access to the
battery connector pins on the Bottom board. Refer to Bottom Cover on
page 6–23.
4. Attach the voltmeter across the test resistor in Figure 6–16.
5. Connect the AC adapter to the WFM 90 or WFM 91 Handheld Waveform,
Vector, Picture, and Audio Monitor.
6. Check for a voltage reading of +2 VDC on the voltmeter with the WFM 90
or WFM 91 Handheld Waveform, Vector, Picture, and Audio Monitor turned
on, and a reading of +8 to +9 VDC with the instrument turned off. The
voltage will slowly rise when the instrument is turned off.
7. If the voltage reading in the previous step was correct, replace the batteries.
If the voltage reading was incorrect, replace the Bottom board.
WARNING. To prevent electric shock and high-voltage arcing, do not operate the
Backlight power supply with the LCD module removed. High voltages in excess
of 1 kV can be present on the Backlight power supply leads when operated open
circuit.
If the LCD module is removed, always remove the Backlight board before
powering up the instrument for test.

Low-Voltage Power Supply
Use the following procedure to check that the low-voltage power supplies are
operating properly before proceeding to Fault Symptom Table.
1. Disconnect the AC adapter from the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor.
2. Remove any installed batteries. See Batteries on page 6–21.
3. Remove the top cover. See Top Cover on page 6–7.
4. Connect the AC adapter and turn on the instrument.
5. Check the supply voltages listed in Table 6–4:

6–34

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Table 6–4: Low-voltage power supplies
Supply

Test Point

Output

Ripple

+8 V

J9, pin 13

40 mV

30 mV

–8 V

J9, pin 14

40 mV

30 mV

+5 V

J9, pin 15

25 mV

60 mV

6. If the low-voltage power supplies are operating properly, proceed to Fault
Symptom Table.
7. If any of the voltages are out of specification, check the two fuses on the
Bottom board.
CAUTION. Do not use a soldering iron larger than 18 W or you may damage the
circuit board and the surrounding circuitry.
8. If a fuse is bad, remove the AC adapter and replace the fuse before you retest
the low-voltage power supplies.
9. If both of the fuses are ok, replace the Bottom board.
NOTE. Be sure to remove all modules one at a time to isolate the Bottom board in
cases where a supply might be excessively loaded.

Fault Symptom Table
Be sure to check the low-voltage power supplies before proceeding with the
following procedure:
1. Disconnect the AC adapter from the instrument.
2. Remove any installed batteries. See Batteries on page 6–21.
3. Remove the top cover. See Top Cover on page 6–7.
4. Remove the bottom cover. See Bottom Cover on page 6–23.
CAUTION. To avoid breaking the circuit boards, do not tighten the circuit board
vise too tightly.
5. Secure the instrument circuit boards in the circuit board vise.

WFM 90 and WFM 91 Service Manual

6–35

Troubleshooting Procedures

6. Connect a 75% color bar test signal to the VIDEO IN connector and connect
the VIDEO OUT connector to the picture monitor.
7. Locate your fault symptom in Table 6–5 and go to the flowchart indicated to
isolate the faulty module.
Table 6–5: Fault symptom table
Symptom

Flowchart

No display after pressing the front panel ON button

page 6–37

Graticule is ok, but the Waveform display is distorted or not visible

page 6–38

Graticule is ok, but there is no Vector display

page 6–39

Graticule is ok, but the Audio display is distorted or not visible

page 6–40

No display in the Picture display mode

page 6–41

Bad graticule and menu, but Picture display mode ok

page 6–42

Display all white

page 6–43

Waveform display mode sweep not triggered

page 6–44

Vector display unlocked

page 6–45

Vector display jitter

page 6–46

Distorted vectors in Vector display

page 6–46

Control problem

page 6–47

Menus horizontally unlocked in Picture display mode

page 6–48

Dim or blotchy display

page 6–49

All display modes are bad except Picture, when no menus are displayed

page 6–49

Troubleshooting Flowcharts
The troubleshooting flowcharts provide a series of steps to follow which should
result in you isolating the faulty module. Each flowchart is directly related to a
fault symptom listed in Table 6–5.
Figure 6–32 on page 6–50 illustrates the connector and pin locations of the
circuit board connectors listed in the troubleshooting flowcharts.

6–36

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use this procedure if
there is no display after
pressing the front panel
ON button.

Is the
Backlight broken?
(The Display module
will have a rattle
inside.)

Replace the
Backlight in the
Display module.

Yes

No
Press the front
panel ON button
and then the PIX
mode button.

Is the
VIDEO OUT
signal good?

No
Replace the Top board.

Yes
Is the
Backlight on?
(Look in the end of
the Display module
where the high
voltage is
attached.)

Yes

Remove the AC adapter
and then remove the
Display module and the
Backlight board. Reattach
the AC adapter and leave
the VIDEO IN and VIDEO
OUT cables attached.
Power up the instrument.

J16-9 = 1 VDC to 3 VDC as VIEW is
adjusted in the CONFIGURE menu.
J16-10 = (DSYNC) 0 to +600 mV
compsync
J16-14 = (SEL_EXVID) +5 VDC in PIX
mode and 0 VDC in Waveform mode
Select PIX Mode, No Menu,
(Use 100% flat field test signal.)
J16-6 = (B) 2 VDC blanking level/2.5 V
peak video
J16-7 = (G) 2 VDC blanking level/2.5 V
peak video
J16-8 = (R) 2 VDC blanking level/2.5 V
peak video
Select WFM Mode + MENU
(Use 75% color bar signal.)
J16-2 = (B) 0 to +1.3 V
J16-3 = (G) 0 to +1.3 V
J16-4 = (R) 0 to +1.3 V

Are all of these
signals correct?

Yes

Check for bad or
misaligned Display
module interface cable.
If cable is ok, replace
the Display module.

Test the Backlight power supply:
Disconnect the AC Adapter. Remove the Display
module. Attach a 10 kW ≥2 W resistor between
the high voltage connectors using a pair of
jumper wires. Attach an oscilloscope probe to the
end of the resistor attached to the orange
connector. Connect the oscilloscope ground lead
to the GND test point on the Bottom board. Set
the oscilloscope to 50 V/div. Reconnect the AC
adapter and power up the instrument.

Is there
400 VAC as
measured on
the
oscilloscope?

Check the Display drive signals:
(Probe J16 from the back of the Bottom
board.)

If the DISP BRT signal is bad, replace the
Bottom board.
If the DSYNC signal is bad, replace the Top
board.
If the SEL_EXVID signal is bad, replace the
Top board.
If the RGB video is bad, replace the Bottom
board.
If the Raster Drive signals are bad, replace
the Top board.

Check Backlight power supply inputs:
J20-1 = Ground
J20-2 = 12 VDC Vin (1 Vpp ripple)
J20-3 = 5 VDC (Backlight Enable)
J20-4 = 1.25 VDC (1.25-1.75 VDC as the
Backlight brightness is changed using the
CONFIGURE menu)

Yes
Replace the Backlight in the
Display module.

Are all of the
Backlight power
supply inputs
good?

Yes

Replace the
Backlight board.

No
Replace the Bottom
board.

Figure 6–17: Flowchart for no display

WFM 90 and WFM 91 Service Manual

6–37

Troubleshooting Procedures

Use this procedure when
the graticule is ok, but the
Waveform display is
distorted or not visible.

Remove the Display module and Backlight
board. Power up the instrument and select
DEFAULT PRESETs from the CONFIGURE
menu. Select the Waveform display mode.

Check the VIDEO IN signal:
J14-2 = 1.3 Vpp, 0 VDC
blanking level.

Is the
VIDEO IN
signal OK?

Check the input DC clamp circuit:
Short J14-4 to the GND pin on the
Bottom board with a jumper wire.
Check the VIDEO IN signal:
J14-2 = 1.3 Vpp, 0.3 VDC
blanking level.

Yes

Replace the Input board.

Yes
Replace the Bottom board.

Check the Waveform display
mode horizontal and vertical
deflection signals:
(J9 is on the back of the Top
board.)
J9-1 = 1.3 Vpp, 2 VDC (vert.)
J9-3 = 2.2 Vpp, 2.3 VDC (horiz.)

Are the
deflection
signals
ok?

Is the
VIDEO
IN signal
ok?

No
Replace the Bottom board.

Yes
Check the horizontal and vertical size control
voltages:
(These voltages are set in the CALIBRATION
MENU.)
J9-7 = 0.9 VDC
J9-8 = 1.2 VDC

Are the size
voltages ok?

Yes

Replace the Top board.

No
Replace the Bottom board.

Figure 6–18: Flowchart for distorted waveform display

6–38

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use this procedure when
the graticule is ok, but
there is no Vector display.

Remove the Display module and Backlight
board. Power up the instrument and select
DEFAULT PRESETs from the CONFIGURE
menu. Select Vector display mode.

Check the VIDEO IN
signal:
(J14 is on the Bottom
board.)
J14-2 = 1.3 Vpp, 0 VDC

Is the
VIDEO
IN signal
ok?

Go to Figure 6–18.

Yes
Check the vector
deflection signals
(B-Y/R-Y):
(J9 is on the back of the
Top board.)
J9-1 = 1.3 Vpp, 2.5 VDC
J9-3 = 0.6 Vpp, 2.5 VDC

Are the vector
deflection signals
ok?

Replace the Bottom board.

Yes
Replace the
Top board.

Figure 6–19: Flowchart for no vector display

WFM 90 and WFM 91 Service Manual

6–39

Troubleshooting Procedures

Use this procedure when
the graticule is ok, but the
Audio display is distorted
or not visible.

Remove the Display module and the
Backlight board. Power up the instrument
and select DEFAULT PRESETs from the
CONFIGURE menu. Select the Audio
display mode. Attach an audio input signal
from 0 to +8 dbu.

Check the AUDIO IN signal:
(J15 is on the Bottom board.)
J15-4 = Check for a gain of X1 above
input signal level. The Audio Amplifier
gain is always X1 in +8 dbu. The signal
level should change as different
reference dbu levels are selected from
the menu.

Is the
AUDIO IN
signal ok?

Replace the Input board.

Yes
Check the audio deflection signals:
(J9 is on the back of Top board.)
J9-1 = 1 Vpp, 2 VDC
J9-3 = +1 V to +3.8 V ramp with a
35 ms period

Are the audio
deflection signals
ok?

Replace the Bottom board.

Yes
Replace the
Top board.

Figure 6–20: Flowchart for bad audio display

6–40

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use this procedure when
there is no display in the
Picture display mode.

Is there a
display in any
other operating
mode (except
WIP)?

Go to Figure 6–17.

Yes
Remove the Display module and the Backlight board.
Power up the instrument. Connect a 100% flat field test
signal to the VIDEO INPUT. Select the Picture
display mode.

Check the Display drive signals:
(Probe J16 from the back of the Bottom
board.)
J16-6 = (B) 2 VDC, 2.5 V peak video
J16-7 = (G) 2 VDC, 2.5 V peak video
J16-8 = (R) 2 VDC, 2.5 V peak video

Are the
Display drive
signals
ok?

Replace the
Bottom board.

Yes
Check the SEL_EXVIDEO signal:
(Probe J16 from the back of the Bottom
board.)
J16-14 = +5 VDC in PIX mode

Is the
SEL_EXVIDEO
signal ok?

No
Replace the Top board.

Yes
Replace the Display
module.

Figure 6–21: Flowchart for no picture display

WFM 90 and WFM 91 Service Manual

6–41

Troubleshooting Procedures

Use this procedure when the graticule
and menu are bad, but the PIX mode is
ok (moderate to severe vertical flutter).

Perform the Raster VCO
adjustment, if possible, in
the Adjustment procedures.

Check the Raster VCO control
signal:
(J9 is on the Top board.)
J9-6 = Approximately 10 mVDC

Is the
Raster VCO
control signal
ok?

No
Replace the Bottom board.

Yes
Replace the
Top board.

Figure 6–22: Flowchart for bad graticules and menus

6–42

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use this procedure when
the display is all white.

Remove the Display module and Backlight board. Connect
the AC Adapter and power up the instrument.

Check the Display drive signals:
(Probe J16 from the back of the Bottom board.)
J16-9 = +1 to +3 VDC as VIEW is adjusted in the CONFIGURE menu.
J16-10 =( DSYNC) 0 to 0.6 V compsync
J16-14 = (SEL_EXVID) +5 VDC in PIX mode/0 VDC in Waveform
mode
Select the PIX Mode, No Menu,
(Use 100% flat field test signal.)
J16-6 = (B) 2 VDC blanking level/2.5 V peak video
J16-7 = (G) 2 VDC blanking level/2.5 V peak video
J16-8 = (R) 2 VDC Blanking/2.5 V peak video
Select WFM Mode + MENU
(Use 75% color bar signal.)
J16-2 = (B) 0 to +1.3 V
J16-3 = (G) 0 to +1.3 V
J16-4 = (R) 0 to +1.3 V

Are
all of these
signals
correct?

Replace the
Bottom board.

Yes
Replace the
Display module.

Figure 6–23: Flowchart for all white display

WFM 90 and WFM 91 Service Manual

6–43

Troubleshooting Procedures

Use this procedure when
the Waveform display
mode sweep is not
triggered.

Remove the Display module and Backlight board. Connect
the AC Adapter and power up the instrument. Select
INT REF using the CONFIGURE menu.

Check for vertical and horizontal sync pulses:
(J9 is on Top Board.)
J9-18 = TTL level V-rate sync locked to the input signal.
J9-19 = TTL level H-rate sync locked to the input signal.

Are the
sync
pulses
ok?

Check the REF IN signal:
(J14 is on Bottom Board)
J14-9 = 1.2 Vpp, +1.3 VDC
blanking level.

Replace the
Input board.

Yes
Replace the Top board.

Is the REF
IN signal
ok?

Yes
Replace the Bottom board.

Figure 6–24: Flowchart for untriggered waveform display

6–44

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use this procedure when
the Vector display is
unlocked.

Remove the Display module and Backlight board.
Connect the AC Adapter and power up the instrument.
Select INT REF using the CONFIGURE menu.

Is the
Waveform display
triggered?

Go to Figure 6–24.

Yes
Check the Subcarrier Regenerator Oscillator
(SRO) control voltage:
(J9 is on the Top board)
J9-12 = approximately 1 VDC

Is the SRO
control signal
a DC
voltage?

Yes

Check the IFsc signal:
(J9 is on the Top board)
J9-43 = 300 mV filtered
square wave.

No
This problem can be caused by either the Top or Bottom
boards, and can only be determined by replacing these
boards one at a time.

Is the
IFsc signal
ok?

Yes
Replace the Bottom board.

No
Replace the Top board.

Figure 6–25: Flowchart for unlocked vector display

WFM 90 and WFM 91 Service Manual

6–45

Troubleshooting Procedures

Use this procedure when
there is Vector display jitter.

This problem can be caused by either the Top or
Bottom boards, and can only be determined by
replacing these boards one at a time.

Figure 6–26: Flowchart for vector display jitter

Use this procedure when
the vectors are distorted in
the Vector display mode.

Perform the following steps in the Adjustment
Procedures using the CALIBRATION menu:
Vector Quadrature Phase
Vector Gain and X5 Gain Phase

Does this
remedy the
problem?

Yes
Problem solved.

No
Check the IFsc and QFsc signals:
(J9 is on the Top Board)
J9-42 = 400 mVpp filtered square wave
J9-43 = 300 mVpp filtered square wave

Are the
IFsc and QFsc
signals
ok?

Yes
Replace the Bottom board.

No
Replace the Top board.

Figure 6–27: Flowchart for distorted vectors

6–46

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use this procedure when
there is an instrument
control problem.

Do menu
selections change as the
front panel buttons are pressed,
and does the graticule
appear ok?

Yes
Replace the Bottom board.

Do some
front panel keys work,
and some
do not?

Yes

Remove the Keypad from Top board and clean
the contacts located under the carbon buttons.
Replace the Keypad.

No
Other control problems include:
The instrument does not respond to front panel
key presses after being turned on.
All display modes are bad or not visible after the
instrument is turned on.

Replace the Top Board first. These problems
can be caused by either the Top or Bottom
boards, and can only be determined by
replacing these boards one at a time.

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

WFM 90 and WFM 91 Service Manual

6–47

Troubleshooting Procedures

Use this procedure when the menus
are horizontally unlocked (tearing) in
the Picture display mode.

Does the
input signal have
noisy sync?

Yes
Correct the problem on the input signal.

No
Check the horizontal and vertical sync
signals on the Bottom board:
(J9 is on Top board.)
J9-18 = VSYNC is a TTL Level (locked to
Video IN V-sync)
J9-19 = HSYNC is a TTL Level (locked to
VIDEO IN H-sync)

Are the
VSYNC and HSYNC
signals good and locked
to the video
input signal?

Yes
Replace the Top board.

No
Replace the Bottom board.

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

6–48

WFM 90 and WFM 91 Service Manual

Troubleshooting Procedures

Use this procedure when the
display is dim or blotchy.

Replace the Backlight
in the Display module.

Figure 6–30: Flowchart for dim or blotchy display

Use this procedure when all
of the display modes are bad
except Picture when no
menus are displayed.

Replace the Top board.

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

WFM 90 and WFM 91 Service Manual

6–49

Troubleshooting Procedures

Connector Diagram
Figure 6–32 illustrates the connector and pin locations of the circuit board
connectors listed in the troubleshooting flowcharts.

Fuses
J15
Bottom
board

J14

J16 as seen from the
back of the Bottom board

J20

J16
Ground test point

Top
board

J9 as seen from the front
of the Top board

View of the Top
and Bottom boards
as seen from the
keypad side

J9–13 = +8 V
J9–14 = –8 V
J9–15 = +5 V

Figure 6–32: Circuit board connector and pin locations

6–50

WFM 90 and WFM 91 Service Manual

Options

Options and Accessories
This section lists the instrument options and accessories that can be ordered for
the WFM 90 or WFM 91 Handheld Waveform, Vector, Picture, and Audio
Monitor. Refer to Parts Ordering Information on page 8–1 for information on
how to order parts for this instrument. Refer to Replaceable Parts List on
page 8–5 for the Tektronix, Inc., part numbers to use when ordering replacement
parts.

Options
The options listed below can be ordered with the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor.
H

Option A1 — 220 V Wall Unit Power Adapter, European TUV

Option A2 — 240 V Wall Unit Power Adapter, UK

Option A3 — 240 V Wall Unit Power Adapter, Australia

Option A6 — 100 V Wall Unit Power Adapter, Japan

Option M2 — 5 years Warranty/Remedial Service

Option M8 — 4 Calibration/Performance Tests

Option 33 — Travel-line package which includes:
H

NiCad battery pack

Viewing hood

Desk flip stand

Carrying case — used for carrying this instrument and a Pathfinder
TSG 90-Series Signal Generator

WFM 90 and WFM 91 Service Manual

7–1

Options and Accessories

Accessories
The standard accessories are shipped with every instrument while the optional
accessories must be ordered separately.
The part numbers to use when you order any of the following accessories are
listed in Mechanical Parts List on page 8–7.

Standard Accessories

Optional Accessories

7–2

The standard accessories for the WFM 90 or WFM 91 Handheld Waveform,
Vector, Picture, and Audio Monitor are listed below:
H

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

120 V Wall Unit Power Adapter, North American

Carrying pouch

The optional accessories available for the WFM 90 or WFM 91 Handheld
Waveform, Vector, Picture, and Audio Monitor are listed below:
H

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

NiCad battery pack

Desk stand

Viewing hood

Carrying Case for this instrument and a Pathfinder TSG 90–Series Signal
Generator

WFM 90 and WFM 91 Service Manual

Replaceable Parts

Replaceable Parts List
This section contains a list of the replaceable modules for this instrument. Use
this list to identify and order replacement parts.

Parts Ordering Information
Replacement parts are available through your local Tektronix, Inc., Field Office
or representative.
Changes to Tektronix instruments are sometimes made to accommodate
improved components as they become available and to give you the benefit of
the latest circuit improvements. Therefore, when ordering parts, it is important to
include the following information in your order:
H

Part number

Instrument type or model number

Instrument serial number

Instrument modification number, if applicable

If you order a part that has been replaced with a different or improved part, your
local Tektronix, Inc., Field Office or representative will contact you concerning
any change in part number.

Module Servicing

Refer to Service Offerings on page xv for information on the service offerings
that Tektronix, Inc., provides for this instrument.

WFM 90 and WFM 91 Service Manual

8–1

Replaceable Parts List

Using the Replaceable Parts List
Table 8–1 describes each column in the replaceable parts list.
Table 8–1: Replaceable parts list column descriptions

Cross Index–Mfr. Code
Number to Manufacturer

Abbreviations

Instrument Accessories

8–2

Column Name

Description

Fig. & Index Number

Items in this column are referenced to the exploded view item
numbers.

Tektronix Part Number

Use this part number when ordering replacement parts from
Tektronix.

Serial No. Effective

This column indicates the instrument serial number at which the
part was first effective. No entry indicates the part is good for all
serial numbers.

Serial No. Discont’d

This column indicates the instrument serial number at which the
part was discontinued. No entry indicates the part is good for all
serial numbers.

Qty

This column indicates the quantity of parts used.

Name & Description

An item name is separated from the description by a colon (:).
Because of space limitations an item name may sometimes
appear incomplete. Use the U.S. Federal Catalog handbook H6-1
for further item name identification.

Mfr. Code

This column indicates the code of the actual manufacturer of the
part. (Code to name and address cross reference is located after
this page.)

Mfr. Part Number

This column indicates the actual manufacturer’s or vender’s part
number.

The Mfg. Code Number to Manufacturer Cross Index for the mechanical parts
list is located immediately after this page. The cross index provides codes,
names, and addresses of manufacturers of components listed in the mechanical
parts list.
Abbreviations conform to American National Standards Institute (ANSI)
standard Y1.1—1972.
The part numbers for the standard and optional accessories available with this
instrument are located at the end of the replaceable parts list.

WFM 90 and WFM 91 Service Manual

Replaceable Parts List

Manufacturers Cross Index
Mfr.
Code

Manufacturer

Address

City, State, Zip Code

0DWW6

MICRO POWER ELECTRONICS

7973 SW CIRRUS DRIVE
BLDG 22

BEAVERTON, OR 97008

0GV90

GLOBTEK INC

186 VETERANS DRIVE

NORTHVALE, NJ 07647–2303

0KB01

STAUFFER SUPPLY CO

810 SE SHERMAN

PORTLAND, OR 97214–4657

0LXM2

LZR ELECTRONICS INC

8051 CESSNA AVENUE

GAITHERSBURG, MD 20879

14310

AULT INC

7300 BOONE AVE NORTH
BROOKLINE PARK

MINNEAPOLIS, MN 55428

39951

AROW COMPONENTS & FASTENERS INC

AROW COMPONENTS & FASTENERS, INC.
31012 HUNTWOOD AVE.

HAYWARD, CA 94544

73743

FISCHER SPECIAL MFG CO

111 INDUSTRIAL RD
PO BOX 76500

COLD SPRINGS, KY 41076

75915

LITTELFUSE TRACOR INC
SUB OF TRACOR INC

800 E NORTHWEST HWY

DES PLAINES IL 60016–3049

80009

TEKTRONIX INC

14150 SW KARL BRAUN DR
PO BOX 500

BEAVERTON, OR 97077–0001

83285

STEWARD MFG CO

1200 E 36TH ST
PO BOX 510

CHATTANOOGA, TN 37401–0510

93907

CAMCAR DIV OF TEXTRON INC

ATTN: ALICIA SANFORD
516 18TH AVE

ROCKFORD, IL 611045181

94222

SOUTHCO, INC.

210 N BRINTON LAKE RD

CONCORDVILLE, PA 19331

TK1415

CABOT SAFETY CORP

7911 ZIONSVILLE RD

INDIANAPOLIS, IN 46268

TK1416

SHARP CORP

22–22 NAGAIKE–CHO
ABENO–KU

OSAKA, JAPAN

TK2427

A/D ELECTRONICS INC

10421 BURNHAM DRIVE NW, BLDG #4

GIG HARBOR, WA 98332

WFM 90 and WFM 91 Service Manual

8–3

Replaceable Parts List

1
2
3
4

5
6

A5 40

8
39

9
10

A2 38

11
12

15
18

16
17

19 A4
35

A1
42

34
21
33
32

23
43

30
29
28

24
25

Figure 8–1: Exploded view

8–4

WFM 90 and WFM 91 Service Manual

Replaceable Parts List

Replaceable Parts List
Fig. &
Index
Number

Tektronix
Part Number

10–1

202–0338–10

CASE,TOP:POLYCARBONATE,WFM90

80009

202–0338–00

202–0338–20

CASE,TOP:POLYCARBONATE,WFM91

80009

202–0338–20

–2

378–0418–00

LENS,DISPLAY:POLYCARBONATE,CLEAR,
E/HARDCOAT

80009

378–0418–00

–3

348–1436–00

PAD,CUSHION:CUSHION PAD FOR
BACKLIGHT,E.A.R.,LS1512,PSA20 1 SIDE,0.250 X
3.100 X 0.125

80009

348–1436–00

–4

348–1437–00

PAD,CUSHION,LCD:CUSHION PAD,LCD,E.A.R.
LS1512,PSA20 1 SIDE,0.250 X 11.000 X 0.125

80009

348–1437–00

–5

174–3287–00

CA ASSY,SP:FLAT FLEX,FLX,20,26 AWG,0.050 CTR,
4.0 L,CUT&STRIP X RTANG,PCB,STAGGERED

80009

174–3287–00

–6

131–5148–00

JACK,POWER DC:PCB,MALE,RTANG,2.0 MM DIA
PIN,7 MM H X 3.3 MM TAIL,3 COND,W/SWITCH,
MTG POST,DC

TK2427

ADC–016

–7

211–0294–00

SCREW,MACHINE:M3 X 0.5 X 10MM,
PNH,STL,CDPL,T–10 TORX DR

0KB01

211–0294–00

–8

131–5798–00

CONN,JACK PHONE:PCB,FEMALE,RTANG,3 POS,
W/SHUNT,3.5MM ID,0.354 H X 0.137 TAIL,
5 TERMINAL,W/O THD

0LXM2

SJ100

–9

348–1442–00

LCD FOOT:LCD LOCATOR FOOT

80009

348–1442–00

–10

348–1425–00

MOUNT,RESILIENT:COMPRESSION MOUNT,
0.280 DIA X 0.320 THK COMPOSITE W/0.2 L 4–40
THD STUD

TK1415

MB–100–UC04–H

–11

159–0378–00

FUSE,WIRE LEAD:2.0A,125V,1 SEC MIN – 60
SECTROLLED

75915

R473 002–T1R

–12

210–0586–00

NUT,PL,ASSEM WA:4–40 X 0.25,STL CD PL

0KB01

ORDER BY
DESCRIPTION

–13

213–0774–00

SCREW,TPG,TF:M3–0.5 X 10MM L,TORX DRIVE
BLACK ENDURION

93907

ORDER BY
DESCRIPTION

–14

220–0497–00

NUT,PLAIN,HEX:0.5–28 X 0.562 HEX,BRS CD PL

73743

ORDER BY
DESCRIPTION

–15

210–1039–00

WASHER,LOCK:0.521 ID,INT,0.025 THK,SST

0KB01

1224–02–00–0541C

–16

333–4144–00

PANEL,REAR:POLYCARBONATE

80009

333–4144–00

–17

671–3044–00

CIRCUIT BD ASSY:INPUT BOARD

80009

671–3044–00

–18

174–3288–00

CA ASSY,SP:DISCRETE,CPD,2,24 AWG,300V,
TEFLON,2.3 L,1X2,0.079(2MM),RCPT X 1X4,
0.079(2MM),RC

80009

174–3288–00

–19

671–3045–00

B010100

B011542

CIRCUIT BD ASSY:BACKLIGHT,WFM90

80009

671–3045–00

671–3045–01

B011543

B023805

CIRCUIT BD ASSY:BACKLIGHT,WFM90

80009

671–3045–01

671–3045–02

B023806

B029999

CIRCUIT BD ASSY:BACKLIGHT,WFM90

80009

671–3045–02

671–3045–03

B030000

CIRCUIT BD ASSY:BACKLIGHT,WFM90

80009

671–3045–03

671–3045–00

B010100

B010440

CIRCUIT BD ASSY:BACKLIGHT,WFM91

80009

671–3045–00

671–3045–01

B010441

B021044

CIRCUIT BD ASSY:BACKLIGHT,WFM91

80009

671–3045–01

671–3045–02

B021045

B029999

CIRCUIT BD ASSY:BACKLIGHT,WFM91

80009

671–3045–02

Serial No.
Effective

Serial No.
Discont’d

WFM 90 and WFM 91 Service Manual

Qty

Name & Description

Mfr. Code

Mfr. Part Number

8–5

Replaceable Parts List

Replaceable Parts List (Cont.)
Fig. &
Index
Number

Tektronix
Part Number

Serial No.
Effective

671–3045–03

B030000

CIRCUIT BD ASSY:BACKLIGHT,WFM91

80009

671–3045–03

–20

337–4000–00

SHEILD:BACKLIGHT ECB,0.005 POLYMIDE

80009

337–4000–00

–21

211–0878–00

SCREW:4–40 X 0.5 LONG,PAN HD SCREW,TORX
DRIVE,BLACK ZINC PLATED,W/LOCKING PATCH

0KB01

211–0878–00

–22

214–4636–00

RCPT,TURNLOCK F:RECEPTACLE USED WITH
SOUTHCO SNAP IN STUD

94222

82–35–309–56

–23

200–4201–00

BATTERY,DOOR:MTC,POLYCARONATE

80009

200–4201–00

–24

358–0792–00

BUSHING,RETAINR:STUD RETAINER,SOUTHCO

94222

82–32–401–41

–25

355–0286–00

STUD,TURNLOCK:OVAL HEAD,STL, SOUTHCO

94222

82–11–520–16

–26

346–0279–00

STRAP,CARRYING:1.00 X 11.00 CARRY HANDLE

80009

346–0279–00

–27

348–1428–00

PAD,CUSHIONING:MTL,0.062 THICK PORON

80009

348–1428–00

–28

210–0589–00

NUT,SLFLKG,HEX:4–40 X 0.246,STL CD PL

39951

ORDER BY
DESCRIPTION

–29

334–8830–00

MARKER,IDENT:BATTERY,0.002 MATTE SILVER
POLYESTER,BLACK NOMENCLATURE

80009

334–8830–00

–30

348–1427–00

PAD,CUSHIONING:PAD,CUSHIONING,BATTERY

80009

348–1427–00

–31

202–0339–00

CASE,BOTTOM:POLYCARBONATE

80009

202–0339–00

–32

337–4036–00

SHIELD,ELEC:0.005 VALOX W/0.005 254 PRESSURE
SENSITIVE ADHESIVE ON BACKSIDE,2.050 X 4.650

80009

337–4036–00

–33

214–4627–00

SPRING,CONTACT:BATTERY CONTACT,SINGLE

80009

214–4627–00

–34

214–4628–00

SPRING,CONTACT:SPRING BATTERY
CONTACT,DUAL

80009

214–4628–00

–35

174–3289–00

CA ASSY,SP:DISCRETE,CPD,2,24 AWG,TEFLON,
4.3 L,1X2,0.079 CTR(2MM),PLZ BOTH ENDS,
JST TYPE

80009

174–3289–00

–36

671–3043–00

B010100

CIRCUIT BD ASSY:BOTTOM BOARD,WFM90

80009

671–3043–00

671–3043–01

B011123

B011362

CIRCUIT BD ASSY:BOTTOM BOARD,WFM90

80009

671–3043–01

671–3043–02

B011363

B023820

CIRCUIT BD ASSY:BOTTOM BOARD,WFM90

80009

671–3043–02

671–3043–03

B023821

CIRCUIT BD ASSY:BOTTOM BOARD,WFM90

80009

671–3043–03

671–3263–00

B010100

B010358

CIRCUIT BD ASSY:BOTTOM BOARD,WFM91

80009

671–3263–00

671–3263–01

B010359

B010470

CIRCUIT BD ASSY:BOTTOM BOARD,WFM91

80009

671–3263–01

671–3263–02

B010471

B021056

CIRCUIT BD ASSY:BOTTOM BOARD,WFM91

80009

671–3263–02

671–3263–03

B021057

CIRCUIT BD ASSY:BOTTOM BOARD,WFM91

80009

671–3263–03

Serial No.
Discont’d

B011122

Qty

Name & Description

Mfr. Code

Mfr. Part Number

–37

337–4035–00

SHIELD,ECB:ECB SHIELD,ALUM

80009

337–4035–00

–38

671–3042–00

B010100

B010109

CIRCUIT BD ASSY:TOP BOARD,WFM90

80009

671–3042–00

671–3042–01

B010110

B010502

CIRCUIT BD ASSY:TOP BOARD,WFM90

80009

671–3042–01

671–3042–02

B010503

B010903

CIRCUIT BD ASSY:TOP BOARD,WFM90

80009

671–3042–02

671–3042–03

B010904

B011802

CIRCUIT BD ASSY:TOP BOARD,WFM90

80009

671–3042–03

671–3042–04

B011803

B022965

CIRCUIT BD ASSY:TOP BOARD,WFM90

80009

671–3042–04

671–3042–05

B022966

B023841

CIRCUIT BD ASSY:TOP BOARD,WFM90

80009

671–3042–05

8–6

WFM 90 and WFM 91 Service Manual

Replaceable Parts List

Replaceable Parts List (Cont.)
Fig. &
Index
Number

Tektronix
Part Number

Serial No.
Effective

Serial No.
Discont’d

671–3042–06

B023842

671–3264–01

B010100

B010184

671–3264–02

B010185

671–3264–03
671–3264–04
671–3264–05

B021091

Qty

Name & Description

Mfr. Code

Mfr. Part Number

CIRCUIT BD ASSY:TOP BOARD,WFM90

80009

671–3042–06

CIRCUIT BD ASSY:TOP BOARD,WFM91

80009

671–3264–01

B010524

CIRCUIT BD ASSY:TOP BOARD,WFM91

80009

671–3264–02

B010525

B020839

CIRCUIT BD ASSY:TOP BOARD,WFM91

80009

671–3264–03

B020840

B021090

CIRCUIT BD ASSY:TOP BOARD,WFM91

80009

671–3264–04

CIRCUIT BD ASSY:TOP BOARD,WFM91

80009

671–3264–05

–39

119–4788–00

KEYPAD:ELASTOMERIC,FRONT PANEL,17 KEY

80009

119–4788–00

–40

119–4789–00

DISPLAY MODULE:LCD,234V X 479H,4 INCH,
COLOR,NTSC/PAL,BACKLIGHT,ANALOG RGB IN

TK1416

LQ4RA02

–41

150–0215–00

LAMP:BACKLIGHT,FLUORESCENT,REPLACEMENT
FOR 4 IN SHARP

TK1416

LQ0B01

STANDARD ACCESSORIES

–42

070–8968–00

B010100

B010352

MANUAL,TECH:USERS,WFM90

80009

070–8968–00

070–8968–01

B010353

B021957

MANUAL,TECH:USERS,WFM90

80009

070–8968–01

070–8968–02

B021958

B022965

MANUAL,TECH:USERS,WFM90

80009

070–8968–02

070–8968–03

B022966

MANUAL,TECH:USERS,WFM90

80009

070–8968–03

070–8968–01

B010100

B020560

MANUAL,TECH:USERS,WFM91

80009

070–8968–01

070–8968–02

B020561

B020839

MANUAL,TECH:USERS,WFM91

80009

070–8968–02

070–8968–03

B020840

MANUAL,TECH:USERS,WFM91

80009

070–8968–03

119–4538–00

B010100

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
120VAC 60HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, STANDARD, WFM90

14310

P48121000A220CM

119–5507–00

B021958

AC ADAPTER ASSY:AC ADAPTER W/NOISE
FILTER,STANDARD, WFM90

80009

119–5507–00

119–4538–00

B010100

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
120VAC 60HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, STANDARD, WFM91

14310

P48121000A220CM

119–5507–00

B020561

AC ADAPTER ASSY:AC ADAPTER W/NOISE FILTER,
STANDARD, WFM91

80009

119–5507–00

CASE,CARRYING:DUAL ZIPPER,TEK LOGO IN
VINYL,HAND STRAP,BELT HOOP,TRI–RING,
CLEAR VINYL FRONT

80009

016–1330–00

OPTIONAL ACCESSORIES
070–8969–03

B030871

MANUAL,TECH:SERVICE,WFM90

80009

070–8969–03

B030220

MANUAL,TECH:SERVICE,WFM91

80009

070–8969–03

276–0838–00

B020561

CORE,EM HALF:EMI SUPPRESS,IMPED 298 OHM
AT 100MHZ,PKG,2–HALFS W/ CLAMP,
0.705 X 0.725,1.28 L, WFM91

83285

28A2025–010

386–6787–00

STAND FLIP:METAL

80009

386–6787–00

011–0167–00

COVER,HOOD:PLASTIC

80009

011–0167–00

WFM 90 and WFM 91 Service Manual

8–7

Replaceable Parts List

Replaceable Parts List (Cont.)
Fig. &
Index
Number

Tektronix
Part Number

Serial No.
Effective

Qty

Name & Description

Mfr. Code

Mfr. Part Number

016–1344–00

CASE,CARRYING:CUSTOM CASE FOR WFM90 ,
TSG90

80009

016–1344–00

119–4540–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
220VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, EUROPEAN, WFM90

14310

D48121000A220CM

AC ADAPTER ASSY:AC ADAPTER W/NOISE FILTER,
EUROPEAN, WFM90

80009

119–5424–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
220VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, EUROPEAN, WFM91

14310

D48121000A220CM

AC ADAPTER ASSY:AC ADAPTER W/NOISE FILTER,
EUROPEAN, WFM91

80009

119–5424–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
240VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, UNITED KINGDOM,WFM90

14310

F48121000A220CM

AC ADAPTER ASSY:AC ADAPTER W/NOISE FILTER,
UNITED KINGDOM, WFM90

80009

119–5423–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
240VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, UNITED KINGDOM,WFM91

14310

F48121000A220CM

AC ADAPTER ASSY:AC ADAPTER W/NOISE FILTER,
UNITED KINGDOM, WFM91

80009

119–5423–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
240VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, AUSTRALIAN, WFM90

0GV90

WD377E1000CRA12C
N

AC ADAPTER ASSY:AC ADAPTER W/NOISE FILTER,
AUSTRALIAN, WFM90

80009

119–5421–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
240VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, AUSTRALIAN, WFM91

0GV90

WD377E1000CRA12C
N

AC ADAPTER ASSY:AC ADAPTER W/NOISE FILTER,
AUSTRALIAN, WFM91

80009

119–5421–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
100VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, JAPANESE, WFM90

14310

G48121000A220DM

AC ADAPTER ASSY:AC ADAPTER W/NOISE
FILTER,JAPANESE, WFM90

80009

119–5508–00

POWER SUPPLY:12W,12V 1.0A,UNREGULATED,
100VAC 50HZ,183CM CABLE W/5.5MM OD,
2.1MM ID RT ANG CN C, JAPANESE, WFM91

14310

G48121000A220DM

AC ADAPTER ASSY:AC ADAPTER W/NOISE
FILTER,JAPANESE, WFM91

80009

119–5508–00

119–5424–00

B021958

119–4540–00

119–5424–00

B020561

119–4541–00

119–5423–00

B021958

119–4541–00

119–5423–00

B020561

119–4542–00

119–5421–00

B021958

119–4542–00

119–5421–00

B020561

119–4539–00

119–5508–00

B021958

119–4539–00

119–5508–00

8–8

Serial No.
Discont’d

B020561

WFM 90 and WFM 91 Service Manual

Diagrams

Diagrams
This section contains the interconnect diagram for the WFM 90 and WFM 91
Handheld Waveform, Vector, Picture, and Audio Monitor.

A1 Input
Board

Video In

A2 Top Board

A3 Bottom
Board

J4
J11

J14

J13

Ref In
J5

J12

J15

J10

Test only
12

Video Out
J6
Audio In
J20

A4 Backlight
Board

J25

W1 W2

DC in 11–18V

W3 W4

J17

Backlight

NiCad Battery Pack

J19

6 C Cell Batteries

J21

J16

A5 LCD Display
Module

Figure 9–1: Interconnect diagram

WFM 90 and WFM 91 Service Manual

9–1

Diagrams

9–2

WFM 90 and WFM 91 Service Manual

Source Exif Data:

File Type                       : PDF
File Type Extension             : pdf
MIME Type                       : application/pdf
PDF Version                     : 1.2
Linearized                      : Yes
Encryption                      : Standard V1.2 (40-bit)
User Access                     : Print, Copy, Fill forms, Extract, Assemble, Print high-res
Create Date                     : 1998:09:01 12:45:03
Producer                        : Acrobat Distiller Daemon 3.02b for Solaris 2.3 and later (SPARC)
Author                          : ilenen
Creator                         : Interleaf, Inc.
Title                           : Document:
Modify Date                     : 1998:09:01 14:09:05
Page Count                      : 154
Page Mode                       : UseOutlines

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Tektronix Stereo System Wfm90 Users Manual

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