W591

This document is a proprietary schematic diagram, copyrighted by Digital Equipment Corporation in 1969, for a "Positive Level to DEC Level Receiver" (model W591). It is intended solely for test and maintenance purposes.

The circuit depicts multiple, largely identical receiver channels, each designed to convert positive logic input levels (e.g., inputs E, H, L, P, T) into DEC-compatible logic levels (e.g., outputs D, F, K, N, S). Each channel utilizes discrete components including resistors, diodes (primarily D662, equivalent to 1N645), and two types of transistors (DEC 3009B, equivalent to 2N3009, and DEC 4258, equivalent to 2N4258) for level shifting and buffering.

The receiver operates with multiple power supply rails, specifically +5V, +10V, -15V, and -3V, and includes common ground connections (C, M GND). General component specifications are provided, stating that resistors are 1/4 W, 5%; capacitors are 0.01 MFD; and diodes are D664 (equivalent to 1N3606), though D662 is predominantly labeled throughout the schematic. A conversion chart is included to cross-reference DEC transistor and diode part numbers with their EIA equivalents.