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Diode Test

  1. To check positive diode, connect a battery lead in series with a test light to B+ terminal. Connect other lead, in turn, to each phase terminal. See Figure. Reverse connections. Bulb should light in 1 direction only.
  2. To check negative diode, connect a battery lead to the heat sink. Connect the other battery lead, in series with a test light, in turn, to each phase terminal. See Figure. Reverse connections, and bulb should light in 1 direction only.
  3. To check the diode trio, connect a battery lead to a phase terminal. Connect the other lead, in series with a test light, to the other side of the diode. See Figure. Reverse connections. Bulb should light in 1 direction only.
  4. Check other 2 diodes in the same way. If bulb lights in both directions, or fails to light in either direction, the diode being tested is defective.