This cellphone after use in a damp environment for some time, there the person calling can not hear voice, but then hear each other's voice can be heard. Teardown found that smaller, lighter machines inside a dust and moist, clean dust and blown dry after water vapor, then took the microphone and found phone contact with the motherboard's gold-plated contact surface has Black oxide, while testing the microphone (electret microphone RX1k stalls can be measured with multimeter) is normal. This machine in a very small microphone attached to the cylindrical conductive rubber, with the Board received a gold-plated contacts gold plated contact surfaces, damp has started serious Black oxide. Use sand cloth lightly sanded smooth before, plus put some sewing machine oil to prevent sanding surface oxidation (Note: when light sanding and polishing after grinding down the motherboard, fine metal dust cleaning to prevent falling into the other IC Board fine foreword at the foot and cause a short circuit triggered a new failure). Also use alcohol to clean rounded conductive rubber, blow dry machine trial, troubleshooting. To totally eradicate the problems, application of thin copper wires the microphone with the soldering on the motherboard.dCvservice manual download site