Installing and Using the VT420 Video Terminal

Solving Problems and Getting Service

This chapter describes what to do if you have a problem with the VT420. The chapter also describes the terminal's power-up self-test and screen error messages.

Operating Problems

Table 10-1 lists some possible operating problems and their suggested solutions. Check this list before calling for service. If you need service, see the "Digital Service" section in this chapter.

Power-Up Self-Text

Every time you turn the terminal on, the VT420 automatically runs a power-up self-test. This test checks the operating status of many of the terminal's internal parts.

Successful test: If the test is successful, a VT420 OK message appears on the screen. The keyboard bell should ring once.

Error: If the keyboard bell does not ring or it rings similar to a telegraph sound, this indicates a self-test error. The keyclick and bell sound patterns are codes that provide service personnel with information about the terminal's operating condition.

Error Messages

If the VT420 fails the power-up self-test, the terminal may display one of the error messages in Table 10-2. Only qualified service personnel should try to correct these problems. If possible, note the error message that appears, then call for service.

Table 10-1 Common Operating Problems
Problem Suggested Solution
The VT420 does not turn on when you set the power switch to 1 (on). Make sure the VT420 power cord is plugged into the wall outlet. Check the power at the wall outlet by plugging in a lamp.
The screen's text is not balanced on the left and right or top and bottom. Align the text by using the screen align feature in the Set-Up Directory screen (Chapter 5).
The printer does not print.

Make sure the printer is plugged in and its power switch is on. Make sure the cable connection between the printer and VT420 is tight.

Make sure the printer assignment feature in Global Set-Up is set to the active session (Chapter 5). If the setting is correct, Printer: Ready should appear on the status line at the bottom of the screen.

Make sure all communication settings on the terminal and printer (such as transmit rate, receive rate, and parity) match.

Data on the screen does not scroll. The Hold indicator is on. Clear the terminal by using the Clear Comm field in the Set-Up Directory screen (Chapter 5).
The screen is blank, except for a blinking cursor at the lower-right corner of the screen.

The CRT saver feature in the Global Set-Up screen (Chapter 5) may be on. Press any key to reactive the screen display.

Make sure the brightness and contrast controls (Chapter 4) are adjusted correctly.

The bell tone does not ring when you turn the VT420 on. The keyboard indicator lights do not flash. Make sure the keyboard is connected to the terminal.
The host system's software does not recognize the VT420 terminal type. Change the setting of the terminal ID feature in the General Set-Up screen (Chapter 3).
Power to the terminal is lost, and you cannot log in to your host system. When power is restored to the terminal, make the F4 (Session) key the first key you press. Refer to Chapter 7 for the procedure to restore an interrupted session.
Table 10-2 Screen Error Messages
Error Message Problem and Solution
Error - 1
Nonvolatile memory (set-up storage) is not operating. Turn the terminal off and on. When you turn the terminal on, the set-up features will return to the default state. If the problem continues, call Digital Customer Service.
VT420 RS-232 Port Data
Error - 2
The problem is inside the terminal. Call Digital Customer Services.
VT420 RS-232 Port Controls
Error - 3
The problem is inside the terminal. Call Digital Customer Services.
VT420 Keyboard
Error - 4
  1. Make sure your keyboard is plugged in.
    If it is,
  2. Turn the terminal off and on.
    If the problem continues,
  3. Try another keyboard, if you have one.
    If the new keyboard works, replace the old keyboard.
  4. If the new keyboard does not work, the problem is inside the terminal. Call Digital Customer Services.
VT420 DEC-423 Port
Error - 5
The problem is inside the terminal. Call Digital Customer Services.
VT420 Printer Port
Error - 6
The problem is inside the terminal. Call Digital Customer Services.
The keyboard's keyclick and margin bell make sound patterns similar to a telegraph. The problem is inside the terminal. Call Digital Customer Services.

Digital Service

Digital provides a wide range of maintenance programs that cover small systems and terminals. These include on-site, carry-in, and mail-in repair services. You can use these programs to select a plan that best meets your service needs.

On-Site Hardware Services

Digital offers fast, low-cost, quality maintenance performed at your site by Digital-trained Service Specialists. There are several on-site services available.


DECservice provides preferred on-site service, with a guaranteed response time when equipment is located within a specified distance of the service facility. DECservice guarantees a continuous repair effort until service is restored. You can choose the hours of coverage, up to 24 hours a day, 7 days a week.


Basic offers priority response during regular business hours, Monday through Friday.

Site SERVIcenter

If you have at least 50 terminals and can provide workspace at your site, Digital will provide an on-site technician or a predetermined, periodic time interval. The terminals can include a variety of models (for example, VT200s, VT300s, and VT420s).

Per Call

This noncontractual offering provides on-site repair based on time and materials. Per call service is available during regular business hours, Monday through Friday.


DECall is similar to per call service, but has an annual retainer fee. DECall gives you on-site service at a fixed fee per repair call.

Off-Site Hardware Services

Carry-In SERVIcenters

Digital SERVIcenters are located in major cities around the world. They offer convenient, cost-effective repair service with a 48 hour turnaround time. Both contract and per call coverage is offered.


DECmailer is a mail-in service for module and subassembly repairs. DECmailer provides five day turnaround and express 24 hour turnaround.

Software Service

Software service products are available for host resident applications.

How to Get Service

Digital has a central service center in your area to help you keep your system running at peak efficiency. To find out more about Digital's hardward and software service offerings

In the United States

Call 1-800-554-3333 during regular business hours and ask for Customer Assistance.

Outside the United States

Contact your local Digital Customer Services Office.