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开机后出现连续“哒哒”声,无光无声。经观察“哒哒”声来自主板总电源继电器KL801时通时断所发出,而继电器通断受微处理器TMP47C433AN—3849⑧脚输出高电子控制。故障出现时测⑧脚电压,随着“哒哒”声该电压在4.9～0V之间跳动,可见故障与该电压不正常有关。分析原因主要有三个:①微处理器本身不良;②4MHz晶振不良;③复位电压不正常。查微处理器供电5V正常,换晶振也无效,测(33)脚复位电压,发现无5V电压,查V003集电极输出电压正常,再
Continued after the boot “da da” sound, dull and silent. After the observation of “da da” sound from the motherboard when the total power supply relay KL801 off issued by the intermittent, while the relay off by the microprocessor TMP47C433AN-3849⑧ foot output high electronic control. When the fault occurs test ⑧ foot voltage, with the “da da” sound the voltage beating between 4.9 ~ 0V, we can see that the fault is not related to the voltage. There are three main reasons for the analysis: ① microprocessor itself is bad; ② 4MHz crystal oscillator is poor; ③ reset voltage is not normal. Check the microprocessor 5V power supply normal, for the crystal oscillator is invalid, test (33) pin reset voltage, found no voltage 5V, check the collector voltage V003 normal output voltage, and then