Engineering Change Order

This Engineering Change Order details hardware modifications for the M7726 module (used in CL8, PDP8, and PDP11 systems) to address two specific technical issues:

• Erase gate delay: Current delay is insufficient for all track locations, which impacts drive interchangeability.
• Head load settling time: Sensitivity to mechanical adjustment is leading to potential CRC errors.

Correction: The fix involves replacing four integrated circuit (IC) ROM chips with updated versions to resolve the timing and sensitivity issues. Specifically, ICs E14, E4, E17, and E7 are being updated with new ROM part numbers (23257A2, 23258A2, 23259A2, and 23260A2, respectively). The old ROMs are to be obsoleted, and the new ones added as replacement parts.

Effectivity:

• Modules in manufacturing must be reworked immediately as parts become available.
• For ongoing module production, the change will be phased in as existing ROM stock is depleted.