To repair the image fault of C-arm, the dosimeter (if not, darkbox instead) is placed in front of the image intensifier. Press the fluoroscopy foot brake to check whether the C-arm is radiated. If there is no ray. If the fault occurs in the control circuit, the high voltage and current should be checked. If there are rays, it is the fault in image acquisition and processing. The digital oscilloscope is used to test whether the output signal of CCDBl is normal or not. If the waveform is normal, the image intensifier and the camera are checked. If the waveform is abnormal, the fault occurs in the image processing part of the C-arm. The replacement method is used to check the image processing parts.