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该机接通电源放音正常,约30分钟后出现交流声,且越来越大,两只功放集成块LM1875的温度随交流声的出现迅速上升,几分钟后左右声道放音含混不清,将音量电位器4R57、4R58关至最小,交流声仍然存在。根据故障现象判断,其故障点在功放电路或电源电路中。测量功放集成电路A22、A23各引脚电压,当负表笔接③脚时,①、②、④脚均约为
The machine connected to the power to play properly, about 30 minutes after the exchange of voices, and more and more, the two amplifier block LM1875 temperature rise rapidly with the emergence of hum, a few minutes after the left and right channel playback ambiguous , The volume potentiometer 4R57, 4R58 close to the minimum, hum still exists. According to the phenomenon of failure to determine the point of failure in the power amplifier circuit or power circuit. Measuring amplifier IC A22, A23 pin voltage, when the negative pen then ③ pin, ①, ②, ④ feet are about