Barclays Branch Controller Maintenance Guide (Mk IV)

This document is the "Barclays Branch Controller MKIV Maintenance Guide," first published in December 1985 by Digital Equipment Company Ltd. It provides comprehensive instructions and information for the maintenance, installation, and fault finding of the Barclays Branch Controller Mark IV system, which is a package of DEC equipment built into a BA123-A3 'World Box'.

The guide is structured into main sections and detailed appendices:

• Core Maintenance Procedures (Sections 1-9): These sections cover general aspects of the system, including an introduction to its components (CPU, memory, storage, communications), physical overview of the 'World Box' (access panels, fans), detailed use of diagnostic tools and LED error codes, installation sequences, backplane utilization, power supply specifics, Barclays' fault reporting procedures, and a list of field-replaceable units (FRUs) for the main enclosure.
• Detailed Component Information (Appendices A-N): These appendices provide in-depth instructions and data for specific core and optional hardware modules such as the KDJ11-B CPU, MSV11-QA memory, RQDX2/3 disk controllers, RD53 disk drives, TQK50/TK50 tape drives, and various communication modules. For each component, details include removal/installation steps, board layouts, jumper/switch configurations, fault codes, and specific testing procedures.

The document also includes important cautions and notes regarding safety, equipment handling, and administrative procedures for component replacement, emphasizing communication with Barclays' support services during fault situations.