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1 故障现象 在点片时,用70KV,200毫安曝光时,控制台内耦变压出现较响的蜂鸣声,电源电压明显下降,毫安指示偏低且不稳,在曝光终了时指针还瞬间上冲,与此同时高压发生器内可以听到较响的嗡嗡声。胶片明显感光不足。当转换到透视时,从60KV开始曝光,逐步加大到90KV,控制台面仪表均正常而且无异常声音。2 故障分析 x线机在通高压时,出现mA表指示颤动且偏低,同时电源电压降增大,高压发生器出现嗡嗡声,这在一般x线机中均预示着高压次级击穿故障。但这一现象在本机仅用大焦点片时出现;在用小焦点透视时又一切正常,而且高压放电及高压侧绝缘破坏的程度,取决于次级的千伏值,与毫安无关。也就是说在点片时用70KV就出现了上述现象,而透视时用90KV都显示正常。这就排除了高压元件击穿的可能性,既然排除了高压侧故障的可能性,无疑故障就发生在低压侧。在此结合本机的线路特点来进行分析。
1 failure phenomenon in the spot, with 70KV, 200 mA exposure, the console internal pressure changer sounded a relatively loud beep, the power supply voltage dropped significantly, the mA indicator is low and unstable, the pointer at the end of the exposure It also rushed up instantly, and at the same time a loud buzzing noise was heard in the high voltage generator. The film is significantly insufficient in photosensitivity. When switching to perspective, the exposure starts from 60KV and gradually increases to 90KV. The console meter is normal and there is no abnormal sound. 2 Failure Analysis When the x-ray machine passes high voltage, the mA meter indicates that the tremor is low and the power supply voltage drops, and the high-voltage generator hums. This indicates that the high-voltage secondary breakdown occurs in the general x-ray machine. malfunction. However, this phenomenon occurs when the unit uses only a large focal spot; when using a small-focus perspective, everything is normal, and the degree of breakdown of the high-voltage discharge and the high-voltage side insulation depends on the secondary kilovolt value, and has nothing to do with milliamps. That is to say, the above phenomenon occurs when 70 KV is used for spotting, and 90 KV is used for normal viewing. This eliminates the possibility of breakdown of the high-voltage component. Since the possibility of a high-side fault is ruled out, no doubt the fault occurs on the low-voltage side. In this analysis, the circuit characteristics of the unit are combined.