scope:

Description of Driving Event:

Qualification test failures of RM2679 transformers were discovered after vibration screening. Posttest analysis of the failed transformers revealed there were gaps between internal contacts. Further analysis revealed that wires had broken off where the transformer coil wire is soldered to larger terminals.

Root cause: Nicks were discovered on the coil winding wire near its attachment point. Further investigation determined that assembly personnel were using mechanical strippers to strip the coating off the ends of the wire. These nicks became stress concentrators leading to subsequent failure during vibration testing.