G850

This document is a proprietary schematic diagram for the S.C.R. (Silicon Controlled Rectifier) Motor Driver, model G850 (part number G850-0-1, Revision P), copyrighted by Digital Equipment Corporation in 1965. It is provided for test and maintenance purposes only.

The circuit diagram details the components and connections of the motor driver, which operates with A+10V and B-15V power supplies. Key components include:

• Multiple transistors (e.g., Q1-Q4, specified as DEC 3638B or 2N2646).
• Numerous diodes (e.g., D1-D14, D16-D20, with IN4003 as a default, and types like D662/IN645, D664/IN3606, IN758).
• A 2N4443 SCR (D15) as the main switching element for motor control.
• Resistors (mostly 1/4W, 10% tolerance), a capacitor (C1), and a transformer (T1).
• A Motorola MDA 942-5 bridge rectifier.

The document also includes a "Transistor & Diode Conversion Chart" mapping Digital Equipment Corporation part numbers to their EIA equivalents, and general component specifications.