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故障现象:放音、录音均正常,调频调幅均无声,连一点噪音也没有。分析:由于放音、录音均正常,可以断定功放级工作正常,故障出在收音电路和转换开关上,检查转换开关,接触良好,从而进一步判定是伴音电路故障。该机由于是立体声收录机,首先检查解码集成块TDA7343发现各脚电压均正常,信号也能从①脚输入,可以判定是收音中放电路TDA7640及外围元件
Symptoms: playback, recording are normal, FM amplitude modulation are silent, not even a little noise. Analysis: Due to playback, recording are normal, you can conclude that the amplifier level is working properly, the fault is in the radio circuit and the transfer switch, check the transfer switch, good contact, and thus further determine the sound circuit fault. The aircraft is a stereo recorder, first check the decoding integrated block TDA7343 found that the normal voltage of each foot, the signal can also be input from the foot, you can determine the radio discharge circuit TDA7640 and peripheral components