DECtape Control Type 551

This maintenance manual provides comprehensive documentation for the DECtape Control Type 551, which operates in conjunction with Type 555 Dual DECtape Transports and the PDP-6 Arithmetic Processor via the Data Control Type 136. The document includes:

• System Description: Details on the DECtape recording format, Manchester recording, mark track format, block structure, and register functions (Control, Status, Read-Write Buffer).
• Theory of Operation: Explanations of initialization, command decoding, timing track/mark track operations, and automatic error checking.
• Maintenance: Comprehensive procedures for both preventive maintenance (mechanical checks, power supply, and module-specific checks) and corrective maintenance (system troubleshooting, aggravation techniques, and repair guidelines).
• Engineering Data: An appendix providing guidance on engineering drawings, logic signal symbols, and circuit symbols used throughout the documentation.