R181

This document is a schematic diagram for a DC Carry Chain, designated R181-0-1, Revision D, created by Digital Equipment Corporation and copyrighted in 1964.

Key details include:

• Purpose: The schematic is for test and maintenance purposes, featuring proprietary circuits.
• Circuitry: It depicts a cascade of seven transistor stages (Q1-Q7), each with associated diode logic (D1-D7) and resistor networks. A more extensive diode array (D25-D52) forms a complex output section.
• Power Supply: The circuit operates with +10V (A), Ground (C), and -15V (B) supply rails.

• Components:

  • Transistors: DEC 3639 B (equivalent to EIA 2N3639B).
  • Diodes: Primarily D-662 (equivalent to EIA IN645) and D-664 (equivalent to EIA IN3606).
  • Resistors: Generally 1/4 Watt, 5% tolerance, with values ranging from 1,500 Ohms to 100,000 Ohms.
  • Capacitor: One 0.01 MFD capacitor (C1) is present.

• Documentation: Includes a "Transistor & Diode Conversion Chart" providing EIA equivalents for DEC-specific part numbers, and revision history with drawing and engineering dates from September/October 1964.