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故障现象:摘机后受话器长啸一声后无声,免提相同,其余正常。分析检修:该机手持受话器和免提接收电路大同小异且同时损坏的可能性较小,所以主要查公共信号通路,手持受话器接收电路原理如附图所示。根据故障先查无声后查啸声,摘机状态下在IR端注入感应信号无反应,说明故障在C1之后。当测量Ql的c极电压时,突然出现声音且免
Symptom: Pick up the phone after the whistle loudly silent, hands-free the same, the rest of normal. Analysis and maintenance: The machine handset receiver and hands-free receiver circuit is more or less the same as the possibility of damage is small, so the main check public signal path, handset receiver circuit as shown in the figure. According to the fault check the first silent after howling, pick-off state in the IR end of the induction signal injection reaction, indicating that the fault after C1. When measuring the c-pole voltage of Ql, the sound suddenly appears and is free