Abstract: At approximately 10:20 a.m. on June 1, 1990, Employee #1, of Hughes Aircraft in Buena Park, CA, was on a four-man maintenance team that was replacing a broken circuit breaker on a chiller unit. The unit is de-energized by using the controller box, and the circuit breaker on the chiller unit is bypassed to keep the unit operating until a replacement breaker is installed. The unit is shut off by means of a time delay switch, which automatically restarts after a 30-second delay. Employee #1 was checking the tension on the V-belt pulley drive when part of his right index finger was amputated. The machine had not been adequately de-energized, as required by safety standards.