M7711

This document is an Engineering Change Order (ECO) log for the M7711 LA30 Control Logic A Module, covering changes made between April 1971 and June 1972. It details various hardware and functional issues discovered in the module and the corresponding corrections.

The problems addressed include:

• Assembly and Manufacturing Defects: Misaligned resistor (R2).
• Functional Errors: Flag loss during PDP-11 power-down, loss of CARRIAGE RETURN characters due to timing window issues, unreliable WAKEUP circuit operation leading to printer logic reset failures, spurious flags from the Demand Line Driver on power-down, and faulty power-fail features caused by incorrect pull-up configurations (double pull-up on PINIL).
• Electrical/Signal Integrity: Excessive loading on the AH2 signal input.
• Recovery Issues: Slow recovery time for a demand one-shot circuit.
• Documentation: Requirement for special documentation to guide the rework of M7711 revision "C" boards to revision "E."

Corrections involved actions such as relocating components, redesigning circuits, replacing drivers, buffering signals, adding pull-ups, changing resistor values, and implementing new etch patterns. Most changes mandated immediate in-plant rework, with some also requiring field retrofits or phase-in during manufacturing.