DECbridge 500/600 Problem Solving Guide

This document, "DECbridge 500/600 Series Problem Solving" (Order Number: EK-DEFEB-PS-002, July 1991), is a technical manual primarily intended for qualified service personnel responsible for troubleshooting and servicing the DECbridge 500/600 series of network bridges to the field-replaceable unit (FRU) level. Effective use of the manual requires knowledge of Fiber Distributed Data Interface (FDDI) and IEEE 802.3/Ethernet.

The DECbridge 500/600 series are store-and-forward devices designed to interconnect 100-Mb/s FDDI networks with up to three 10-Mb/s IEEE 802.3/Ethernet network segments. These bridges are composed of four main logic modules: Application Processor (AP/AP2), Network Interface (NI/NI(3)), Fiber Interface (FI), and Queue Manager (QM).

The manual provides a comprehensive approach to problem-solving, detailing:

• The use of self-test diagnostics (automatic on power-up or remote invocation).
• Interpretation of local LED indicators for status and fault conditions, including detailed troubleshooting tables and flowcharts.
• Visual inspection procedures for initial fault diagnosis.
• Instructions for performing loopback testing using specific connectors to isolate faults within the bridge, cable, or connected device.
• Procedures for measuring FI (Fiber Interface) optical power to verify signal integrity.

Additionally, the document outlines step-by-step removal and replacement procedures for all FRUs (logic modules, card cage, power supply, fan assembly, and backplane), with strong emphasis on essential safety precautions such as disconnecting AC power and utilizing ESD ground straps.

Technical information provided includes physical descriptions, configuration switch settings, detailed LED functions, block diagrams, descriptions of each module's function, power supply characteristics (shutdown, thermal protection, DC OK signal), fan assembly monitoring, and comprehensive product specifications (physical, electrical, environmental, and cabling). Appendices offer configuration guidelines for connecting to FDDI and Ethernet networks, FDDI connection rules and keying, and a list of related documentation.