FCO DNSBX-0001, Potential for Electrical Short in the Transformer

This Field Change Order (FCO DNSBX-0001) addresses a potential electrical short in the transformer of the H7720-AA power supply units used in various DECnis 600 platforms. The problem arises from "carbonization" in the transformer windings during manufacturing hipot testing, leading to power supply overheating, unexpected device failure, and sudden loss of power, sometimes accompanied by smoke. Despite these symptoms, Digital Product Safety has determined it is not a safety hazard as the enclosure contains the malfunction.

The solution is to replace all affected power supplies (those below revision C01) with the updated revision C01 or higher (part number EQ-01683-01). Due to the DECnis 600 being a critical networking product, the replacement must be scheduled in advance with customers at a "non-critical" time. Installation involves powering down the system, using static protection, removing the old power supply, installing the new one, and verifying system functionality. Old power supplies are to be returned for upgrade, and the activity must be reported using the LARS form.