VT100 and PDT-11

This document is a "VT100 and PDT-11 Video Terminals Maintenance" manual, published by Digital Equipment Corporation (DEC) in 1979 as a self-paced/lab course for internal use. Its primary purpose is to provide technicians with a comprehensive physical and functional description of the VT100 video terminal to enable major maintenance tasks, including diagnosing problems, locating faulty Field Replaceable Units (FRUs), and performing repairs.

The manual is structured into two main sections:

1. Introduction:

   • General Description: Details the VT100 as a self-contained desktop unit comprising a 12-inch CRT monitor, a 10x10-inch printed circuit board controller, a 95-watt power supply, and an 83-key detached keyboard.
   • Features: Highlights the VT100's capabilities, such as displaying information in 80-column by 24-line or 132-column by 14-line formats (operator/host selectable), supporting US and UK character sets, control codes, and limited graphics using a 7x9 dot matrix. It offers various display options like white on dark/black on white, flashing underline or block cursors, and highlighting (underline, reverse video, blink/bold with option). It supports double-height and double-width characters, jump/smooth scrolling, full-duplex serial asynchronous communication (50 to 19,200 baud, 7 or 8 bits per character, parity options), and includes power-up and loop-back internal diagnostics. Most settings are stored in non-volatile memory (NVR).
   • VT100 Specifications: Provides detailed physical (dimensions, weight, environmental conditions) and display specifications (CRT type, character sizes, active display area, character set, cursor types).
   • VT100 Options: Describes available plug-in options like the Advanced Video Option (AVO) for expanded screen formats (132 columns), additional highlighting features, and the 20mA Current Loop Communication Option for local communication without modems.

2. Physical/Functional Description:

   • This section focuses on the identification, location, and major functions of the nine core Field Replaceable Units (FRUs) crucial for maintenance:
     • Power Supply Assembly: Converts AC line voltage into the four DC voltages (+5V, +12V, -12V, -23V) required by the terminal.
     • DC Power Harness: Distributes power and video drive signals from the power supply to the Terminal Controller PCB and Video Monitor PCB.
     • Terminal Controller PCB: The "brain" of the VT100, housing the microprocessor, memory (ROM/RAM), keyboard interface, EIA communications, and video processor logic, with various connectors for internal and external communication and options.
     • Video Monitor PCB: Generates signals for horizontal/vertical beam deflection, beam modulation (for character display), and rectifies high voltages from the Flyback Transformer for focus and intensity control, featuring multiple adjustments for display quality.
     • Flyback Transformer: Generates the high voltages (e.g., 11.5KV for CRT anode) necessary for the CRT's operation, controlling focus, beam shaping, and brightness.
     • Field Service Replacement CRT Monitor Assembly: A complete assembly replaced if the CRT, Yoke, or Vertical Coil fails.
     • VT100 Keyboard, Keyboard PCB, Speaker, and Keyboard Cable: The components of the detached keyboard assembly responsible for data entry, audible feedback, and communication with the terminal controller.

The document includes a "Course Map" to guide learners through related modules and "Practice Exercises" with solutions to reinforce understanding of FRU functions and connector mappings.