例1:海信TC2122MA型机,TV状态时“黑屏”,无伴音,有字符显示。分析检修:有字符显示,说明显像管及其发光所需条件均设有问题,从而也说明电源与行扫描电路基本正常,故障发生在公用通道或亮度、伴音通道同时存有故障,但几率很小。测显像管阴极KB、KG、KR皆200V,故导致“黑屏”。测视放管V601、V611、V620皆200V,故导致“黑屏”。测机放管V601、V611、V621射极电压皆6.9V,基极5.2V,三管均截止。测LA7680(24)脚7V偏 Example 1: Hisense TC2122MA type machine, TV status “black screen”, no sound, a character display. Analysis and maintenance: a character display, display tube and its lighting conditions are required to have problems, which also shows that the power supply and the line scan circuit is normal, the fault occurred in the common channel or brightness, audio channels at the same time there is a fault, but the probability is very small . Test tube cathode KB, KG, KR are 200V, it led to “black screen.” V601, V611 and V620 are all 200V, which leads to “black screen”. Tester discharge tube V601, V611, V621 emitter voltage is 6.9V, base 5.2V, three tubes are deadline. Measured LA7680 (24) foot 7V bias