There will be some kind of current into the "Ground" terminal on the output (i.e. your computer case) for most small switching power supplies (two-prong without

There will be some kind of current into the "Ground" terminal on the output (i.e. your computer case) for most small switching power supplies (two-prong without separate protective earth pin). This current is caused by the "Y-Capacitor" which goes between the secondary ground/shielding and one of the power inputs. http://electronics.stackexchange.com/questions/216959/what-does-the-y-capacitor-in-a-smps-do http://electronics.stackexchange.com/questions/216959/what-d... This is needed for proper EMI/RF immunity and because of this you often can measure the line voltage (or half of the line voltage, depending on how the Y capacitor is connected internally) on the output pins with a high-impedance multimeter. No significant current can flow, though, because at the line frequency (50 or 60 Hz) the impedance of the Y capacitor (typically 1nF or so) is pretty high (2.5MOhm). For 230V, this would correspond to 0.1mA.