Tektronix WFM90, WFM91 - page 96

Removal and Replacement

6–10 WFM 90 and WFM 91 Service Manual

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.

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