DEC-10-I4AA-D TM10 Maint Aug68

This document is the Maintenance Manual for the TM10 Magnetic Tape Control Unit, published in August 1968 for use with the Digital Equipment Corporation (DEC) PDP-10 computer.

The TM10 controls magnetic tape transports (such as DEC Model TU-20 or TU-79) and comes in two main models:

• TM10A: Interfaces with the PDP-10 via its I/O bus, relying on an executive program and data interrupt for data transfers.
• TM10B: Utilizes the DF10 Data Channel for data transfer between the control unit and PDP-10 core memory, operating under DF10 control after initial program setup.

It supports both 7-track and 9-track tape head configurations:

• 7-track: Offers 200, 556, or 800 bits per inch (bpi) densities, with selectable binary (odd) or BCD (even) parity. It translates 36-bit PDP-10 words into six 7-bit characters.
• 9-track: Operates at 800 bpi (IBM-compatible) and includes a Cyclic Redundancy Check (CRC) character for error detection. It translates 36-bit words into four 9-bit characters (or five 8-bit bytes in "core dump" mode).

The manual details various tape functions and their programming, including:

• Data operations: Read, Read Across Record Boundaries, Read/Compare, Write, Write with Extended EOR Gap, Write End-of-File.
• Positioning operations: Rewind, Space Forward (and to End-of-File), Space Reverse (and to End-of-File). It explains how to issue commands via CONO instructions and monitor status through CONI instructions.

A significant portion is dedicated to the theory of operation, covering NRZ recording, data channel interfaces (especially DF10 for TM10B), initial operation sequences for both TM10A and TM10B, inter-record gap delays, and the detailed logic for read, write, and spacing operations. It also describes various error conditions (e.g., data late, parity, record length incorrect, bad tape, illegal commands) and a "Read-In Mode" for program loading.

Finally, the document provides maintenance procedures, categorized into:

• Preventive Maintenance: Routine mechanical checks, weekly transport timing tests, and monthly power supply and reliability checks.
• Corrective Maintenance: Troubleshooting steps, signal tracing techniques, a list of diagnostic programs (MAINDEC-10 series), and advice for handling intermittent failures. The content assumes familiarity with the PDP-10 Programmed Data Processor and DEC logic symbology.