M664

This document is a proprietary schematic diagram for the Digital Equipment Corporation (DEC) IO BUS DRIVER M664, copyrighted in 1971. It is provided strictly for test and maintenance purposes.

The circuit design utilizes DEC1074H00 NAND gates (E1, E2), DEC4258 transistors (Q1-Q8), and other transistors (DEC6531, DEC6534D), along with various diodes, resistors, and capacitors. It appears to function as a signal conditioning and driving circuit for an I/O bus, converting input signals through logic gates and transistor stages to produce buffered outputs.

Key features and components include:

• Multiple input/output channels processed through a series of NAND gates, diode chains, and transistor drivers.
• A "Crowbar" circuit (featuring transistors Q9, Q10, and diodes D34-D36) likely for overvoltage protection.
• Power supply connections for +5V, -15V, +3V, and +0.8V, with associated filtering capacitors and voltage reference diodes.
• General specifications indicating default values for components like resistors (7.5K, 1/4W, 5%), diodes (D664), capacitors (.01uF, 100V, 20%), and ICs (DEC1074H00).

The document also includes a detailed parts list enumerating all necessary components (including the etched circuit board and a handle), and a transistor and diode conversion chart providing EIA equivalents for DEC part numbers.