FCO DEREP-R001, Quick power fail engages self-test

This document is a Field Change Order (FCO) DEREP-R001, issued on February 13, 1989, to resolve a critical issue in approximately 6,140 DEREP-AA, AB, RC, RD (Revision C1 or below) and DEREP-RA, RB (Revision B1 or below) units. The problem manifests as the DEREP unit failing to reset properly after a quick power failure (less than 300 ms), causing it to enter a continuous self-test loop and never return to normal operation. This FCO incorporates changes from ECOs 54-15586-MK007 and DEREP-MK005.

The solution involves upgrading the affected units by replacing the existing logic module with a new DEREP Logic Module (Part Number 54-15586-01), which is provided in FCO Kit EQ-01521-01. The installation, estimated to take 1.0 hour, requires the unit to be removed from the network, disassembled, and the old logic module carefully replaced with the new one (emphasizing the need for electrostatic discharge precautions). Specific instructions are provided for reassembly, applying new revision markers ("C", "D", "1") to the unit tag based on the DEREP model, and verifying that the unit successfully passes its power-on self-test. The FCO concludes with requirements to update LARS data and the Site Management Guide.