M452

This document is a proprietary schematic diagram for a "VARIABLE CLOCK M452" circuit, created by Digital Equipment Corporation in 1967 for test and maintenance purposes.

The circuit utilizes a combination of discrete components and integrated circuits (ICs) from the DEC74xx series:

• Transistors: Q1-Q4 (DEC3009B, DEC6534B)
• Diodes: D1-D5 (D662, D664)
• Resistors: R1-R15, including a 2000-ohm trimpot (R3) for adjustment.
• Capacitors: C1-C6, including a 35V, 10% tantalum capacitor (C5).
• Integrated Circuits:
  • E1: DEC7440N (Dual 4-input NAND Buffer/Driver)
  • E2: DEC7474N (Dual D-type Flip-Flop)
  • E3: DEC7400N (Quad 2-input NAND Gate)

The schematic indicates power rails of A+5V and +3V, with C GND. It also features a connection for "880 BAUD," suggesting the clock's application in controlling data transmission rates. Standard IC power connections (Pin 7 to GND, Pin 14 to +5V) are specified.

A "Transistor & Diode Conversion Chart" is provided, listing EIA equivalent part numbers for the DEC components used in the design (e.g., DEC3009B is equivalent to 2N3009, D662 to 1N645). General specifications for resistors (1/4W, 5%) and capacitors (0.01 MFD) are also noted.