 The malfunction was especially puzzling because the probe had been given very thorough ground testing without any anomalies occurring.Examination of telemetry records seemed to suggest that the failure had occurred during separation of Ranger 4 from the Agena, at the point where the electrical interface between the two was disconnected and Ranger 4 would have switched to internal power.The behavior of the probe indicated a transformer or inverter malfunction, probably a short circuit caused by loose metal coatings contacting the pins on the power umbilical attaching the probe to the Agena.