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故障现象:收看电视节目有图像,无伴音,而在AV状态下一切正常。分析与检修:该机属于三洋A6机芯,微处理器(CPU)型号为LC864512—5C77,小信号处理集成电路为LA7687A,CPU通过SAB总线和LA7687A传递模拟量控制和状态控制指令。开机输入TV信号,发现图像清晰,色彩艳丽。按动“音量+”键,屏幕下部有音量条格指示并能逐步增加,但加至最大仍无伴音,其他各项操作均正常。结合该机在AV状态下有伴音这一现象,可初步判断CPU电路及伴音通道的公共部分是正常的,问题应该出在TV/AV转换电路及以前,包括TV/AV转换电路、伴音中频形成电路、制式切换和伴音静噪控制电路,并且
Symptoms: watching TV shows have images, no sound, but in the AV state everything is normal. Analysis and Maintenance: This machine belongs to Sanyo A6 movement, microprocessor (CPU) model LC864512-5C77, small signal processing integrated circuit LA7687A, CPU through the SAB bus and LA7687A transfer analog control and status control instructions. Boot input TV signal, found the image clear, colorful. Press the “Volume +” button, the bottom of the screen volume bar instructions and can gradually increase, but still no increase to the maximum, the other various operations are normal. With this machine in the AV state with the sound of this phenomenon can be a preliminary judge the common part of the CPU circuit and sound channel is normal, the problem should be in the TV / AV conversion circuits and before, including TV / AV conversion circuit, sound IF formation Circuit, standard switching and audio squelch control circuit, and