When diagnosing a microwave oven, many problems can be detected merely with careful observation, that is, with the power disconnected. Most tests can be accomplished with the power off and the oven unplugged. We suggest that you leave the "live" testing to the professionals. Nonetheless, certain safety habits must be developed and maintained. If you have experience in troubleshooting electrical equipment, some of these safety precautions may be familiar. However, the high-current potential of the high-voltage circuits in a microwave oven make them possibly life-saving steps.