This paper introduces a fast repair methods of Versa HD volume-modulated accelerator's high voltage
circuit fault: the key points test method. To identify five key points: ①Enter maintenance mode to check
for AFC deviation; ② The magnetron waveform MI and PFN waveform PFN V are detected on the
maintenance terminal board; ③ Detect thyratron waveform; ④ Check the supply voltage of thyratron;
⑤ HT PSU 600 V DC test 600 V normal or not. The waveform or voltage is also measured to efficiently
narrow the fault range to find out the cause of the fault, quick ly remove the fault.