H605

This document is an Engineering Change Order (ECO) log from Digital Equipment Corporation for the H605 LA30 Motor Drive Amplifier, detailing a series of engineering changes and corrections made between April 1971 and September 1973.

The primary and recurring issue addressed is overheating diodes leading to discoloration of printed circuit boards and component failure. Solutions implemented for this included:

• Relocating specific diodes and resistors for better clearance.
• Raising diodes to prevent contact with the board.
• Redesigning the board to provide larger heatsink areas and adding transistors.
• Adding heatsinks to specific diodes and clarifying the correct revision levels for retrofitted boards, including allowing for parts substitution for heatsink clips.

Other significant changes and corrections cover:

• Part number discrepancies: Updating drawings and parts lists to ensure correct connectors are used.
• Performance issues: Addressing irregular carriage performance by replacing a specific resistor.
• Documentation and process control: Correcting typographical errors, updating documentation to reflect accurate revision levels, and cancelling a previous ECO (H605-00006) due to redundancy and incorrect specifications (H605-0006A).

Most changes required immediate in-plant rework or phased-in implementation, with many also stipulating field retrofits for units already shipped, often including estimated time for installation and testing.