Power supplies which use capacitors suffering from the capacitor plague may experience premature failure when the capacitance drops to 4% of the original value.[not in citation given] This usually causes the switching semiconductor to fail in a conductive way. That may expose connected loads to the full input volt and current, and precipitate wild oscillations in output.
Failure of the switching transistor is common. Due to the large switching voltages this transistor must handle (around 325 V for a 230 VAC mains supply), these transistors often short out, in turn immediately blowing the main internal power fuse.