G932

This document is a schematic diagram for the Digital Equipment Corporation (DEC) TU-IO Capstan Servo Preamplifier, model G932, designed in 1970.

Key features and information:

• Purpose: It's a preamplifier for a capstan servo system, responsible for processing control and feedback signals to manage tape drive operations.
• Proprietary Nature: The schematic is explicitly stated to be proprietary to Digital Equipment Corporation, copyrighted in 1970, and furnished only for test and maintenance purposes.
• Circuit Components: The design extensively uses transistors (e.g., DEC6534, DEC2219), diodes (e.g., D664, D672), resistors, and capacitors. The core amplification is handled by an operational amplifier (E1, identified as a DEC307).
• Inputs and Outputs: It features multiple power supply inputs (+14V, +8V, -8V, -14V, -15V), control inputs such as "REWIND CAP H," "REWIND H," "REV," "D FOR H," "REV SPEED," and "FWD SPEED," and a "TACK, IN" (likely a tachometer input). The primary output is labeled "AP OUTPUT."
• Component Specifications: Default specifications are provided: resistors are 1.5K, 1/4W, 5%; capacitors are 0.01uF, 100V, 20%; diodes are IN750A; and general transistors are DEC6531 (unless otherwise indicated).
• Conversion Chart: A "TRANSISTOR & DIODE CONVERSION CHART" maps DEC part numbers (e.g., DEC6531, DEC2219, D664) to common EIA or industry equivalents (e.g., MPS6531, 2N2219, IN3605), aiding in component identification and sourcing.