M9680

This document is an Engineering Change Order (ECO) from Digital Equipment Corporation, dated October 1973, for the M9680 DR11-B Maintenance Module, which is part of the PDP-11 Family.

Problem: The module's time constant was too long, causing NPR (Non-Processor Request) latency issues for other peripherals during system diagnostics or exerciser programs.

Correction: The solution involves reducing the value of capacitor C1 to 270 pfd, which sets the nominal time constant to 1.5 microseconds.

Effectivity: All in-plant M9680 modules were to be reworked immediately. Field modules needed to be reworked specifically to allow them to run diagnostics on systems using DR11-B and TM11. The installation and testing time for this change is estimated at 0.5 hours, requiring a specific kit (F1073 -FCO/Prints And Parts).