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The client had been producing the Blood Analysis System for only five years. The design had used a motor control board from another piece of equipment, though, which was of much older vintage. The client realized that a quadrature encoder interface IC on the board had recently gone obsolete, but was confident that a new “direct substitute” from the same IC manufacturer would provide equivalent operation. A full production run of boards were made with the new IC.
Unfortunately, the new boards did not work properly. Although the new IC worked almost identically to the original IC, one minor function operated differently, and none of the boards worked. Production was halted and Bolton Engineering was called in to examine the design and make recommendations.