VT420

This document is the VT420 Service Guide (Order Number EK-VT420-PS.002), published by Digital Equipment Corporation in 1989 (Second Edition 1992).

Its primary purpose is to provide service personnel with instructions on how to service the VT420 monochrome video terminal.

Key topics covered include:

• VT420 Models and Features: Descriptions of various models (North American, Worldwide, PC TERM mode) and their common functionalities.
• Troubleshooting and Testing: Guidance on diagnosing general problems, performing various self-tests (power-up, port loopbacks, screen alignment), and interpreting error codes.
• Removing and Replacing FRUs (Field Replaceable Units): Detailed procedures for replacing major components such as the top cover, CRT/yoke/bezel assembly, terminal board, and keyboard, with a strong emphasis on safety warnings (e.g., high voltages, static protection, and specific CRT disposal guidelines for trained personnel only).
• Adjusting the Video Monitor: Instructions for aligning and adjusting screen settings like brightness, contrast, rotation, horizontal/vertical size, linearity, and focus.
• Using Set-Up: How to access, navigate, change, save, and recall settings within the terminal's set-up screens.
• Appendices: Provide additional information on compatible modems, cables, related documentation, recommended spare parts, and physical/functional diagrams of the terminal's components and pin assignments.

The guide also lists specific tools required for servicing and includes standard disclaimers regarding information changes and software licenses. It is explicitly stated that this guide is intended for Digital's service personnel.