M7670

This document is a schematic diagram for the Digital Equipment Corporation (DEC) Forward B.O.T. (Beginning Of Tape) Timer, model M7670-0-1.

Copyrighted in 1970 and dated early 1971, it is provided for test and maintenance purposes and contains proprietary DEC circuit designs.

The circuit integrates both digital logic and analog/driver stages:

• Digital Logic: Primarily uses DEC74197 binary counters/registers (E1, E2, E4, E5) and DEC7402 logic gates (E3), suggesting timing or counting functions.
• Analog/Driver Stages: Includes multiple transistor stages (Q1-Q6, utilizing DEC3009B, DEC6534D, DEC2219-S transistors), along with associated resistors, capacitors, and diodes (IN4001, IN747A), likely for signal conditioning, buffering, or driving external components related to tape control.

The circuit operates with +5V, -15V, and -2.4V power supplies. General component specifications (e.g., resistor wattage, capacitor voltage) are provided, as well as a conversion chart for DEC-specific transistor and diode part numbers to more common EIA designations.