What might indicate a malfunction in the power supply circuit?

A malfunction in the power supply circuit can indeed be indicated by unusual noise coming from the power supply. This noise often signifies that there is an internal problem, such as a failing component, overheating, or electrical disturbances within the power supply unit. For instance, buzzing, clicking, or humming sounds may suggest issues like loose connections, faulty capacitors, or components that are under stress. When a power supply operates normally, it should do so quietly, so any abnormal sound typically warrants further investigation.

In contrast, consistent output voltage suggests that the power supply is functioning correctly, as it is able to maintain the required voltage levels under load. The absence of a spark at the switch typically indicates that there is no electrical arcing, which can be a normal condition if the circuit is functioning properly. Finally, full functionality of connected devices implies that they are receiving adequate power and operating as expected, which would not point to any issues within the power supply at that moment.