故障现象:开机出现周期性的自动开、关机现象,频率约几秒一次;开机有高压,但未见光栅便关机,关机时屏幕中下部可见暗光。分析与检修:该机为 I~2C 总线彩电,电路如图1所示。测量 B1电压在0～110V 之间周期性变化(正常为115V),其他输出电压也周期性变化。断开 B1供电,用灯泡作假负载开机,灯泡不亮,可听见周期性的起动 Symptom: Power cycle appears automatically on and off phenomenon, the frequency of about a few seconds once; boot with high pressure, but no grating will shut down, turn off the screen when the lower visible darkness. Analysis and Maintenance: This machine is I ~ 2C bus color TV, the circuit shown in Figure 1. Measure the B1 voltage periodically changes between 0 ~ 110V (normal is 115V), the other output voltage also changes periodically. Disconnect the B1 power supply, use the bulb as a dummy load boot, the bulb is not lit, you can hear the periodic start