If the output voltage waveform is a half-wave circuit, it may be caused by the following faults: 1. Rectifier diode is damaged or reversed: when rectifier diode is damaged or reversed, only half-cycle voltage can pass through the circuit, resulting in half-wave voltage output. 2. Failure of the filter capacitor: If the filter capacitor fails, it will cause the capacitor to be unable to smooth the residual waveform and produce half-wave voltage output. 3. Rectifier inductance damage: If the rectifier inductance fails, the input voltage will be unstable and half-wave voltage will be output. 4. The load resistance is too small: the load resistance is too small, and the capacitor cannot be completely discharged, resulting in half-wave voltage output. 5. Damage to other components: If there are problems with other components in the rectifier and filter circuit, such as the voltage regulator, it will also lead to half-wave voltage output.