We are lucky to find a 33 Ohm resistor from electrical shop. Then I pumped the oil out and installed the resistor, at the same time I checked the connectors of transformer, capacitors, choke, thyratron and charging resistors, and found some screws not tight. I tightened the loose screws then. But the x-ray anode could not be triggered normally. I still heard the clicks inside the oil tank and the high voltage could not reach 150 kV yet, which I described in my last email. An interesting phenomena is when I decreased the DC power supply voltage from 30 kV to 20-15 kV, I could not heard the clicks inside the oil tank. What caused this phenomena happened?
I also checked the anode control box, the input signal looks very good. I replaced the high voltage trigger for thyratron, the problem was still there. Till now, I checked every components except the 30 kV DC power supply and the Anode cable connector.