A self-diagnostic apparatus is disclosed which has a transducer, such as a solenoid, for performing a mechanical movement in response to an electrical signal of at least a "first energy," such as a constant DC voltage applied over a predetermined time period. A control device, such as a microprocessor-based control circuit, is used to provide an electrical signal of greater energy than the "first energy" in response to a predetermined condition during operation of the apparatus. Such a predetermined condition may be the arrival of one of a slot machine's reels at a rotational position in which it is intended to be stopped. A diagnostic test initiating device, such as a switch, is used for signalling the start of a test of the transducer. The control device further includes a testing device which is responsive to the diagnositc test initiating device for providing an electrical signal of the first energy to the transducer. A verification device, such as an optical sensor and associated tilt detection circuitry, detects whether the transducer has performed its mechanical movement in response to the first energy electrical signal. An indicator, such as a visual display, responds to the verification device for indicating whether or not the mechanical movement has been detected in response to the diagnostic test initiating device.