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Inspection & Repair: Diodes

  1. Perform a conduction test on all diodes, in both directions, using an ohmmeter. Test the conduction between each terminal and plate. Diode installed on "+" plate is a positive diode which allows current to flow from terminal to "+" plate only; current does not flow from "+" plate to the terminal. A diode installed on the "-" plate is a negative diode and allows current to flow from the "-" plate to the terminal only; current does not flow from the terminal to the "-" plate.
    Fig 1: Rotor Field Coil Conduction Test
    G09342232Courtesy of NOT AVAILABLE
  2. If current flows in both directions, the diode is short-circuited. If current does not flow in either direction, the diode is open. If any diode is defective, replace the entire diode assembly (individual diodes are not serviceable).