TR79-FA DECmagtape (1600 cpi) Maintenance Manual

This document is a maintenance manual for the TR79-FA DECmagtape system, which is a Tape Control Unit (TCU) manufactured by Digital Equipment Corporation (DEC).

Here's a summary of its key aspects:

• Purpose: The manual provides comprehensive information for operating and maintaining the TR79-FA TCU, which interfaces PDP-11 family central processors to Hewlett Packard 7970-E, 9-track, 1600 characters-per-inch (cpi) Magnetic Tape Transports (MTT).
• System Overview: The TR79-FA TCU acts as the interface logic, supporting Direct Memory Access (DMA-NPR) operations. It can drive one master and up to three slave HP 7970-E transports, writing and reading industry-compatible magnetic tape formats at a transfer rate of 40,000 characters per second (with potential for higher speeds). It includes functional sections for address selection, registers, function decoding, gap timing, motion control, read/write buffering, parity checking, and bus control.
• Installation: Details cover site considerations (TCU placement relative to MTT for cable length), specific cabling (Unibus, TCU/MTT), and grounding procedures. It also outlines initial operational checks and acceptance procedures using the MAINDEC-11-DZTRA diagnostic program.
• Operation & Programming: The manual describes the use of Control Register (CR) and Status Register (SR) for program communication with the TCU and MTT. It explains various commands (e.g., Write, Read, Erase, Rewind, Fast Forward, Write Tape Mark, Write ID Burst) and how the system handles interrupts.
• Theory of Operation: This section delves into the detailed recording format (ANSI/IBM compatible, including Identification Bursts, Preambles, Data Records, Postambles, Tape Marks, and Inter-Block Gaps), and the precise timing and control signals involved in writing, reading, erasing, and tape movement. An extensive list of mnemonic signal indicators and terms is provided.
• Maintenance: It outlines comprehensive preventive maintenance schedules for both the TR79-FA TCU (monthly, quarterly, annual) and the HP 7970-E drive (quarterly, semiannual, annual, two-year), covering tasks like inspections, cleaning, electrical checks, and mechanical adjustments (e.g., tension arms, capstan). It also suggests corrective maintenance techniques, primarily using the Test 6 diagnostic program to isolate faults.
• Spare Parts: A list of essential modules and recommended spare parts is included for maintainability.