Tektronix WFM90, WFM91 Description of Key Features

Specifications

1–2 WFM 90 and WFM 91 Service Manual

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-imped-

ance input. The audio input connector is a standard 3-pin XLR connector.

Description of KeyFeatures

Contents

Main Page WARRANTY Page Service Assurance Service Assurance Advantages For Information and Ordering Page Table of Contents Specifications Operating Information Theory of Operation Performance Verification Page List of Figures Page List of Tables Page General Safety Summary To Avoid Fire or Shock Hazards: Observe These Battery Precautions Battery Recycling Symbols and Terms Certifications and Compliances Page Service Safety Summary Page Preface About This Manual Related Manuals Page Introduction Service Strategy Warranty Repair Service Service Offerings Repair or Calibration Service Self Service Before You Begin Page Page Page Specifications Product Description Key Features Description of Key Features Page More Information Characteristics Tables Safety Standards 16 WFM 90 and WFM 91 Service Manual Table 11: Vertical deflection system WFM 90 and WFM 91 Service Manual 17 Table 11: Vertical deflection system (Cont.) Table 12: DC restoration Table 13: Audio mode 18 WFM 90 and WFM 91 Service Manual Table 14: Horizontal deflection system Table 15: Vector mode WFM 90 and WFM 91 Service Manual 19 Table 15: Vector mode (Cont.) 110 WFM 90 and WFM 91 Service Manual Table 16: Synchronization Table 17: Physical characteristics Table 18: Environmental characteristics WFM 90 and WFM 91 Service Manual 111 Table 18: Environmental characteristics (Cont.) Table 19: Power source 112 WFM 90 and WFM 91 Service Manual Table 110: Safety/EMI Page Page Operating Information Installation Mechanical Installation Page Electrical Installation Page Page Side-panel Connectors and Switches Page Special Operating Modes On-screen Readout Default Settings Page Page Theory of Operation Block Diagram Description Bottom Board Input Board Top Board Page Theory of Operation WFM 90 and WFM 91 Service Manual 33 Input Board Figure 31: Simplified block diagram Bottom Board P/O Top Board Page Page Page Performance Verification Summary Verification Page Performance Verification WFM 90 and WFM 91 Service Manual 43 Table 42: Equipment required for performance verification (Cont.) Performance Verification Procedures Conventions Prerequisites Preliminary Setup Sync Separation Sweep Timing and Integral Linearity Vertical Gain and Vertical Magnifier Registration Variable Gain Range and Vertical Position Range Overscan Input and DC Restorer Page Vector Phase Stability Chrominance Bandwidth Page Audio Gain and Page Page Page Adjustment Procedures Summary Adjustment Adjustment Procedures 52 WFM 90 and WFM 91 Service Manual Adjustment Procedures Conventions Prerequisites Adjustment Methodology Preliminary Setup Raster VCO Sweep Timing and Horizontal Mag Registration Vertical Gain and X5 Gain Registration Page Vector Quadrature Phase Vector Gain and X5 Gain Phase Audio Gain Page Page Maintenance Preparation Servicing Prerequisites Electrostatic Damage Prevention Inspection and Cleaning General Care Cleaning After Repair Adjustments Repackaging Instructions Visual Inspection Performance Verification and Readjustments Removal and Replacement Tools Required Removal and Replacement 66 WFM 90 and WFM 91 Service Manual Procedures Top Cover Assembly LCD Display Assembly Page Page Page Page Top Board Assembly Page Page Bottom Board Backlight Board Input Board Assembly Battery Cover Assembly Page Page Batteries Page Bottom Cover Assembly Page Page Page Page Page AC Adapter EMI Suppressor Page Troubleshooting Procedures Battery-Fault Analysis + Low-Voltage Power Supply Fault Symptom Table Troubleshooting Flowcharts WFM 90 and WFM 91 Service Manual 637 No Figure 617: Flowchart for no display 638 WFM 90 and WFM 91 Service Manual Figure 618: Flowchart for distorted waveform display WFM 90 and WFM 91 Service Manual 639 Figure 619: Flowchart for no vector display 640 WFM 90 and WFM 91 Service Manual Figure 620: Flowchart for bad audio display WFM 90 and WFM 91 Service Manual 641 Figure 621: Flowchart for no picture display 642 WFM 90 and WFM 91 Service Manual Figure 622: Flowchart for bad graticules and menus WFM 90 and WFM 91 Service Manual 643 Figure 623: Flowchart for all white display 644 WFM 90 and WFM 91 Service Manual No Figure 624: Flowchart for untriggered waveform display WFM 90 and WFM 91 Service Manual 645 Yes Figure 625: Flowchart for unlocked vector display 646 WFM 90 and WFM 91 Service Manual Figure 626: Flowchart for vector display jitter Figure 627: Flowchart for distorted vectors WFM 90 and WFM 91 Service Manual 647 Figure 628: Flowchart for problems with the instrument controls 648 WFM 90 and WFM 91 Service Manual Figure 629: Flowchart for bad menus in the picture display Page Connector Diagram Page Page Options and Accessories Options Accessories Standard Accessories Optional Accessories Page Page Replaceable Parts List Parts Ordering Information Module Servicing Using the Replaceable Parts List Cross IndexMfr. Code Number to Manufacturer Abbreviations Instrument Accessories WFM 90 and WFM 91 Service Manual 83 Manufacturers Cross Index Mfr. Code Manufacturer Address City, State, Zip Code 84 WFM 90 and WFM 91 Service Manual A2 A3 A4 Figure 81: Exploded view A1 A5 WFM 90 and WFM 91 Service Manual 85 Replaceable Parts List Effective Serial No. Part Number Serial No. Number Tektronix 86 WFM 90 and WFM 91 Service Manual WFM 90 and WFM 91 Service Manual 87 88 WFM 90 and WFM 91 Service Manual Page Page WFM 90 and WFM 91 Service Manual 91 Diagrams Figure 91: Interconnect diagram