Barclays Branch Controller Maintenance Guide (MK II)

This document, published by Digital Equipment Company Ltd. in April 1985, serves as a maintenance guide for the Barclays Branch Controller (MK II). It provides comprehensive instructions for diagnosing and repairing hardware faults within the system.

The guide begins with an introduction to the internal diagnostics, explaining how the system's keyswitch positions (NORMAL, TEST, AUX) influence the power-up test sequences and booting procedures. It then details how to test the system, including power checks, interpreting diagnostic LED patterns to identify Field-Replaceable Units (FRUs) under test, and performing loopback tests.

The core of the document comprises sixteen sections and four appendices, each offering step-by-step procedures for accessing, removing, installing, and configuring specific hardware components (FRUs). These components include various Printed Circuit Boards (PCBs) such as the KDF11-BA (CPU), MSV11-PL (memory), KMV11-B and DLV11-J (communication interfaces), DRV11, and RQDX1 (disk controllers), as well as the RD51 disk drive, RX50 diskette drive, and Gould and H7861 Power Supply Units (PSUs). Each component section is accompanied by diagrams illustrating jumper settings, backplane positions, and cable connections.

Appendices cover cable routing, explain how to interpret LED codes for mark and firmware revisions, provide a detailed procedure for loading Barclays-specific application software, and list all FRUs with their part numbers. Throughout the guide, crucial cautions are provided regarding safety (e.g., removing diskettes before power cycling, switching off power before component replacement) and avoiding damage to sensitive parts like disk drive head positioner flags.