The cause of the light did not turn of dc motor controller

Dc motor controller is the application of a wide range, but may encounter when using the light did not turn. We need according to the reasons for processing. Below small make up the way the cause of the light did not turn. 1. As a result of the armature circuit disconnection; 2. As a result of the armature coil too short; 3. Because of the commutator vertical plate or and head desoldering cause; 4. As a result of the excitation circuit disconnection; 5. As a result of the brush contact undesirable. The above is the cause of dc motor controller is not empty, so I need according to these reasons to find a way.