M666

This document is a proprietary electrical schematic diagram from Digital Equipment Corporation, copyrighted 1970, for an "I.O. BUS RESET M666" circuit (Drawing No. M660-0-1, Revision E). It is explicitly stated to be for test and maintenance purposes only.

The schematic details a complex circuit, likely implemented on a printed circuit board, comprising:

• Power Supply: Connections to -15V, -3V, +5V, and GND, with associated filtering and regulation components (diodes D2-D5, capacitors C2, C5, C6).
• Logic Gates: Utilizes DEC1074HOO integrated circuits (labeled 'EI') configured as various logic functions, providing inputs and outputs for the system.
• Pulse Generation/Drive Circuits: Features transistor-based stages (Q1, Q2 - DEC1008 transistors) with associated diodes (D668), resistors (R1, R2, R5, R6), and capacitors (C4, C8). These stages are driven by logic gates (H2, F2, D1, E1) and incorporate T20 Pulse Transformers (1609651), strongly suggesting their role in generating or shaping reset signals for an I.O. bus.
• Diode-Resistor Networks: Extensive arrays of diodes (D7-D30, D18-D24) and resistors (R8-R31, R20-R24) arranged in multiple interconnected stages (labeled S2, T2, U2, V2, U1, V1, J2, K2, L2, M2, P2, R2), indicating complex signal conditioning, decoding, or distribution pathways for the bus.

The document also includes:

• General Component Specifications: Notes on standard resistor (470Ω, 1/4W, 5%) and capacitor (0.1uF, 100V, 20%) values unless otherwise indicated, along with specific part numbers for transistors (DEC1008), diodes (D664), and ICs (DEC1074HOO), including standard IC pin assignments (+5V on Pin 14, GND on Pin 7).
• Bill of Materials (Parts List): A detailed table listing all components by DEC part number, description (e.g., I.C., Pulse Transformer, Transistor, various resistors, diodes, capacitors, etched circuit board), and quantity.
• Transistor & Diode Conversion Chart: A cross-reference table mapping DEC part numbers to equivalent EIA or other industry-standard numbers for various semiconductors.

In summary, this is a detailed engineering schematic providing a comprehensive blueprint for the functional design, component specifications, and manufacturing information of an "I.O. BUS RESET M666" circuit.