An X-ray imaging system includes an vacuum tube, which is biased by a high voltage power supply connected to the tube by two shielded cables. The cables collectively have a plurality of conductors which are coupled at one end to the high voltage power supply. The other end of each conductor is coupled to a component of the vacuum tube by a separate inductor. During a voltage breakdown of the vacuum tube, the inductors depress electrical current flow between the anode and the cathode of the tube to reduce the erosion of tube components which results from the discharge. This current is in part due to the energy stored in the cable, which is not depressed by conventional current limiting circuits in the high voltage power supply. Voltage limiting devices connected to the tube prevent ringing in the cables from generating excessively high voltage levels.