Digital Equipment VT420 User manual

VT420 Service Guide
Order Number EK-VT420-PS-002
···-----·'"··········· ..
Digital Equipment Corporation

First Edition, December 1989
Second Edition, January 1992
The information in this document is subject to change without notice and should not
be construed as a commitment by Digital Equipment Corporation. Digital Equipment
Corporation assumes no responsibility for any errors that may appear in this document.
The software described in this document is furnished under a license and may be used or
copied only in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment that is not
supplied by Digital Equipment Corporation or its affiliated companies.
Restricted Rights: Use, duplication, or disclosure by the U. S. Government is subject to
restrictions as set forth in subparagraph ( c) ( 1) ( ii ) of the Rights in Technical Data and
Computer Software clause at DFARS 252.227-7013.
Copyright e Digital Equipment Corporation 1989, 1992
All Rights Reserved.
Printed in U.S.A.
The following are trademarks of Digital Equipment Corporation:
SSU, VMS, VT, VT52, VTlOO, VT220, VT320, VT420, and the DIGITAL logo.
ADP is a trademark of Automatic Data Processing, Inc.
Kodak is a registered trademark of Eastman Kodak Co.
OLIVE'l'TI is a registered trademark of Ing. C. Olivetti & C.,·S.p.A.
UNIX is a registered trademarlt of UNIX System Laboratories, Inc.
This document was prepared and published by Educational Services Development and
Publishing, Digital Equipment Corporation.

Contents
About This Guide
Vll
1 VT420 Models and Features
1.1 VT420 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 VT420 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Troubleshooting and Testing
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
2.2.7
2.2.8
2.3
2.4
Troubleshooting .................................. .
VT420 Self-Tests ................................. .
Before You Start ................................ .
How to Type an Escape Character .................. .
Power-Up Self-Test .............................. .
DEC-423 Port Loopback Test (6-Pin) ................ .
RS-232 Port Data Lines Loopback Test
(25-Pin, Worldwide Model Only) ................... .
RS-232 Port Control Lines Loopback Test
(25-Pin, Worldwide Model Only) ................... .
Printer Port Loopback Test (6-Pin) .................. .
Screen Alignment Test ........................... .
Printer Problems ................................. .
Error Codes ..................................... .
4
10
11
11
13
14
16
17
18
18
19
20
iii

iv Contents
3 Removing and Replacing FRUs
3.1 Top Cover........................................ 22
3.2 CRT/Yoke/Bezel Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.3 Terminal Board Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.4 Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.5 CRT Disposal (Digital Service Representatives Only) . . . . . . 38
4 Adjusting The Video Monitor
4.1 Aligning the Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.2 Monitor Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.2.1 Before You Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.2.2 Displaying the Screen Test Pattern . . . . . . . . . . . . . . . . . . 46
4.2.3 Screen Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.2.4
4.2.5
4.2.6
4.2.7
4.2.8
4.2.9
4.2.10
Subcontrast ................................... .
Rotation ...................................... .
Horizontal Width ............................... .
Vertical Height ................................. .
Vertical Linearity ............................... .
Centering ..................................... .
Focus ........................................ .
5 Using Set-Up
47
47
49
49
49
50
50
5.1 Displaying Set-Up Screens. . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.2 Changing Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.3 Saving Set-Up Values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.4 Recalling Set-Up Values............................. 53
A Modems, Cables, and Documentation
A.1 Modems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
A.2 Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
A.3 Related Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Contents v
B VT420 Recommended Spares
B.1 VT420 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
B.2 Recommended Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
B.3 Keyboard Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
C Physical/Functional Diagrams
Index
Figures
2-1 VT420 Video Terminal with Keyboards . . . . . . . . . . . . . . . . . 5
2-2 VT420 Rear Connector Panel and Loopback Connectors . . . . 15
4-1 Set-Up Directory Screens. . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4-2 Screen Align Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4-3 Monitor Adjustment Controls . . . . . . . . . . . . . . . . . . . . . . . . . 45
4-4 Screen Test Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4-5 Rotation and Centering Adjustment. . . . . . . . . . . . . . . . . . . . 48
5-1 Set-Up Directory Screens... . . . . . . . . . . . . . . . . . . . . . . . . . 52
A-1 VT420 Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
C-1 VT420 North American Model . . . . . . . . . . . . . . . . . . . . . . . . 64
C-2 VT420 Worldwide Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Tables
1-1 VT420 Model Differences... . . . . . . . . . . . . . . . . . . . . . . . . . 3
2-1 Troubleshooting the VT420 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2-2 VT420 Self-Test Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2-3 VT420 Display Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . 20

This guide describes how to service the VT420 monochrome video
terminal. The guide is for Digital's service personnel.
The guide has five chapters that cover the following topics:
VT420 models and features
Troubleshooting and testing
Removing and replacing field replaceable units (FRUs)
Adjusting the video monitor
Using set-up
Appendices provide information on the following topics:
Modems, cables, and related documentation
VT420 models and recommended spares
Physical/functional diagrams
Tools Required
You need the following tools to service the VT420 video terminal:
Tool
Anode discharge t.ool
25-pin, RS-232 EIA loopback connector
Metric measuring tape
Two 6-pin, DEC-423 loopback connectors (modularjack)
Phillips screwdriver, number 2
Tuning wand
Video alignment tool
Part Number
29-24717-00
12-15336-00
29-25342-00
12-25083-01
29-11005-00
29-23189-00
29-26128-00
vii

viii About This Guide
Conventions
The following conventions are used in this guide:
Warnings
Cautions
Notes
Set-up features
ANSI keyboard keys
(LK401 or LK421)
PC keyboard keys
(LK443 or LK444)
ANSI keys (with PC
keys)
RS-232
PN
Provide information to prevent personal injury.
Provide information to prevent damage to equipment.
Provide general operatinginformation.
The names of set-up features appear in bold type.
Example: Use the save feature in the Set-Up Directory
screen.
Set-up feature settings and fields appear in this type.
These are the settings that appear on the screen.
Example: Select the Screen Align field.
Appear as normal text in a~
Example: Press the IRetum Ikey.
Appear as bold text in a§!.
Example: Press the la.turn Ikey.
When a PC (LK.4431LK444) command sequence differs
from an ANSI (LK.401/LK421) command sequence, the
PC key sequence appears in parentheses after the ANSI
key sequence.
Example: Press the IRetum I key 4Enter~.
Used to represent electrical standard EIA 232-D, which
replaces electrical standard RS-232-C.
This is an abbreviation for part number.

1.1 VT420 Models
The VT420 is a monochrome text terminal that provides all VT320
features plus enhancements. The VT420 has a 359 mm (14-inch) diagonal
monitor with a flat, antiglare screen. The monitor can display 24, 25, 36,
or 48 lines of text in an 80- or 132-column format. The last line of each
session is reserved for a status line. An attachable tilt-swivel base lets
the user adjust the viewing angle for optimum comfort.
There are three models of the VT420 video terminal:
• North American (VT mode)
• Worldwide (VT mode)
• Worldwide (VT mode and PC TERM mode)
The worldwide models come in two versions, standard and low-emission.
1.2 VT420 Features
The following list includes the features that are common to the North
American and model and two worldwide models. Table 1-1 lists the
differences between the three models. The worldwide model with PC
TERM mode can use the standard ANSI (LK401), short ANSI (LK421),
or PC (LK443/LK444) keyboard. See Installing and Using the VT420
Video Terminal with PC Terminal Mode for details on the features ofthe
different keyboards.

2 VT 420 Models and Features
Common Features
• Two-session capability
• Local copy and paste feature
• Off-screen page memory
• Ability to display 24, 25, 36, or 48 lines/screen
• Screen centering capability
• Screen overscan
• FCC Class A compliance
• Two 6-pin, DEC-423 connectors (One is for the primary host port, and
one is for the secondary host or printer port. Both have DEC-423 local
direct-connect capability.)
• Asynchronous communication up to 38.4Kbits/second
• Four operating modes:
VT400 mode, 7-bit controls (default)
VT400 mode, 8-bit controls
VTlOO mode
VT52 mode
• Ability to store macros
• One full-screen window or two horizontal split-screen windows
• Screen saver
• Character sets:
U.S. ASCII
DEC Supplemental Graphic
ISO Latin Alphabet No. 1
ISO Latin-1 Supplemental
DEC Special Graphic
DEC Technical
Downloadable character set
• Terminal status line
• Keyboard indicator on the last line of the screen
• Ability to disable or enable keys E.!I through ~
• Extended keyboard reports