Provides practical topics related to generators and motors. Begins with general information about cleaning and inspecting DC machines. Presents material on commutators and brushes, and how to troubleshoot commutator problems. Describes how to replace and adjust the brushes to get the optimum performance from the machine. Describes how to troubleshoot grounds, open circuits, and shorts using meters and meggers. Includes procedures for recovering if the exciter loses residual magnetism.