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故障现象:TV状态图像和彩色都正常,而AV状态却五彩色。分析与检修:据分析,故障与音视频切换集成电路NQV03、制式转换解码电路NQ501、以及微处理器NQA01(TMP47C1238ANU068Z)等有关。经查NQV03及其外围元件均无异常,短接(17)、(19)两脚,故障依旧。在故障状态测得色解码集成电路NQ501(21)、(22)、(20)均无输出,说明制式转换电路工作异常。因TV状态NQ501(22)、(21)、(20)脚电压正常,所以故障点在PAL和NTSC开关切换电路。由于PAL/NTSC制式转换受控于微处理器NQA01(31)脚,AV状态测得该脚电压恒于
Symptom: TV status images and colors are normal, but the AV state is colorful. Analysis and Maintenance: According to analysis, fault and audio and video switching integrated circuit NQV03, standard conversion decoding circuit NQ501, and microprocessor NQA01 (TMP47C1238ANU068Z) and so on. The investigation of NQV03 and its external components are normal, short (17), (19) feet, the fault still. In the fault state measured color decoding integrated circuit NQ501 (21), (22), (20) no output, indicating that the work of abnormal conversion circuit. Due to TV status NQ501 (22), (21), (20) pin voltage is normal, so the fault point in PAL and NTSC switch switching circuit. Since the PAL / NTSC conversion is controlled by the microprocessor NQA01 (31) pin, the AV pin voltage is measured to be constant at