FCO DHW4X-F001, Failure on rev B03 DHW4X Logic Board

This Field Change Order (FCO DHW4X-F001) addresses an issue in MicroVAX 3100 Models 30, 40, and 80 equipped with a DHW41/42 asynchronous communications option (referred to as DHW4X) that uses a revision B03 logic board (part number 54-20662-01).

Problem: The B03 DHW4X logic board fails to process data, causing the DHW4X option to "lock-up" or "hang" intermittently due to lost interrupts. This renders attached devices unresponsive and requires a system reboot to clear. The frequency of lock-ups depends on data processing volume, with bar code readers particularly susceptible.

Solution: Replace the faulty revision B03 logic board (54-20662-01) with the updated revision C03 version of the same part.

Procedure Highlights:

1. Quick Check: Disassemble the system, remove the 54-20662-01 logic board, and visually confirm it is revision B03. If so, proceed with the FCO.
2. Prerequisite: Ensure the 3100 CPU module firmware is not V1.1; if it is, FCO KA45-F001 or KA47-F001 must be installed first.
3. Installation: The procedure involves a complete system shutdown, careful disassembly of the enclosure and drive shelves, removal of the old B03 logic board, installation of the new C03 logic board, and reassembly.
4. Verification: After reassembly and power-up, run a SHOW CONFIG command to ensure the system passes self-tests and all devices show an "OK" status.
5. Reporting & Return: The activity must be reported on a LARS form, and the removed B03 module tagged and returned.

This FCO requires field service technicians to use a field service tool kit and an electrostatic kit. Material for the replacement board is typically free of charge for customers under warranty agreements.