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在修理长城、长风、北京牌这些同类型电视机时,发现这些电视机故障很有规律性,最常见的是:大功率电阻器开路,造成几种常见故障。现例举3例以飨读者。例1 故障现象:一台北京8303型54cm彩色电视机开机,无光栅、无伴音,打开后盖目测,发现保险管完好,仔细检查机内元件没有明显的烧焦烧糊现象。分析与检修:开机,测量电源开关管V801集电极,电压为+300V,说明整流滤波电路正常。测开关管V801基极无0.9V启动脉冲电压,说明电源开关启动部分元件有问题,拆下R803 56kΩ、3W测量电阻,发现无穷大已开路。+300V电压经R803、R804电阻器
When repairing the same type of televisions of the Great Wall, Changfeng, and Beijing, we found that these television sets were malfunctioning with the most regularity. The most common ones were the open circuit of high-power resistors that caused several common faults. Now give 3 cases to readers. Example 1 Symptom: A Beijing 8303 54cm color TV turned on, no grating, no sound, open the back cover visual inspection, found the fuse intact, carefully check the machine components no obvious burnt burning phenomenon. Analysis and Maintenance: boot, measure the power switch tube V801 collector, the voltage is +300 V, indicating that the rectifier filter circuit is normal. Measuring switch V801 base no 0.9V start pulse voltage, indicating some problems starting the power switch components, remove the R803 56kΩ, 3W measurement of resistance and found that infinity has been open. + 300V voltage by R803, R804 resistor