This is video tutorial about how to test high voltage diodes. This video shows step by step how to test high voltage diodes. Arrange the diode like the schematic in this video. Connect DC power supply on the input. If the voltage is 6V to 10V the diode is good and connected in the right direction. If the voltage is power supply voltage, the diode is connected backwards or open (bad).  If the voltage is 0 to 2 volts, the diode is shorted (bad). Here is the video: