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故障现象:开机一切正常,但过几分钟后声音逐渐变小直至无声。无论放像还是录制电视节目均如此。关机后过一段时间再开机,又重复上述现象。故障维修:清洗录像机音频磁头后故障依旧。该机音频电路采用BA7751ALS型集成电路。用万用表电压档测试集成块各脚工作电压,均正常。再用示波器测集成块第⑦、⑨、(16)脚及音频输出端,发现第⑦、⑨脚信号正常,第(16)脚及音频输出端信号随着音量的减小而逐渐减小。因此判断为集成块内部损坏。由于无该型号集成块代换,用一只10μF/50V电解电容器直接跨接
Symptom: boot everything is normal, but after a few minutes the sound gradually diminished until silent. This is true whether playing or recording TV shows. Shut down after a period of time and then boot, repeat the above phenomenon. Fault repair: cleaning the recorder audio head still fault. The aircraft audio circuit using BA7751ALS integrated circuit. Voltage meter test with a multimeter block each pin working voltage, are normal. Then use the oscilloscope to measure the ⑦, ⑨, (16) feet and audio output, and found that the ⑦, ⑨ foot signal is normal, the (16) foot and the audio output signal decreases as the volume decreases. Therefore, it is judged that the interior of the manifold is damaged. Since there is no replacement of the type of integrated block, with a 10μF / 50V electrolytic capacitor directly across