According to the symptom, judging this fault is caused by the poor contact of the component. Due to a fault appears after the line pipe is replaced, so the main line tube near the element. When the check to L441, L442 (a tight two-component contact), discovered Squeak varies. Welding two components carefully, I find that the two components of the core framework have different degrees of looseness, sealed with wax after installation testing, troubleshooting. Analysis of the formation of the fault, because L441, L442, close to the tube, replace the tube when shaken in skeleton, caused by the line frequency resonance.