M623

This document is a schematic diagram for the Digital Equipment Corporation (DEC) BUS DRIVER M623, dated 1968. It is explicitly stated to be for test and maintenance purposes and is proprietary to DEC.

The circuit consists of twelve identical driver stages, arranged in two rows of six. Each stage primarily features:

• An integrated circuit (ICs E1, E2, E3 - specifically DEC7402), likely a multi-input gate, handling the input signals.
• An output stage composed of a resistor (R1-R12, 390 Ohm), a transistor (Q1-Q12 - DEC30098 / 2N3009), and a diode (D1-D12 - D664 / 1N3606).

Power is supplied at +5V, with filtering provided by capacitors C1-C4 (including 6.8µF tantalum and 0.01µF disc capacitors). A key note specifies that Pin 7 on each integrated circuit is connected to Ground (GND) and Pin 14 to +5V.

The document also includes:

• A Parts List detailing the reference designators, descriptions, and DEC part numbers for all components (ICs, transistors, resistors, diodes, capacitors).
• A Transistor & Diode Conversion Chart providing EIA equivalents for DEC's internal part numbers (e.g., D664 converts to 1N3606, DEC30098 to 2N3009).
• A Revisions table, indicating updates to the schematic, with the current revision shown as 'F'.