故障现象：F78－300mAX线机在胃肠造影中突然断电，墙上闸刀开关保险丝断，换上新保险丝后开机，透视无X线产生。检修过程：透视时，测量灯丝初级电压为43V，高压初级继电器工作但无输出电压，查为透视高压初级限流电阻烧断。此现象说明高压部分有故障。拆下高压初级连线并短路 Failure phenomenon: F78-300mAX line machine suddenly loses power in gastrointestinal angiography, the wall blade switch fuse is broken, after switching on a new fuse, no X-ray perspective. Maintenance process: In perspective, measuring the primary voltage of the filament is 43V, the high voltage primary relay works but no output voltage, check to see through the high voltage primary current limiting resistor. This phenomenon indicates that the high-voltage part is faulty. Remove the high voltage primary connection and short circuit