Voltage on ungrounded PC case, is it normal?

[JonnyJalapeno]

Hello

So my ungrounded PC case have some potential/voltage on it. Of course when i ground the case there's no voltage reading. But my question is -is it normal for an ungrounded PC case to have voltage? I mean PC power supply, should not pass 12V on the case, it should be isolated, right? No internal electric part that have voltage, inside the PSU should touch the outer case of said PSU right? And motherboard should not leak voltage on the case, instead it should be grounded by the 24pin plug to the PSU[and by standoffs that are connected to a proper grounding circuits on the MB PCB, but these grounding circuits should not leak 12V, right? ], and then to the grounding socket. Even without ground in the wall socket, there should not be a voltage on the pc case, right? Maybe it's induced somehow, by electromagnetic field? Im fairly sure i've built the PC right, without anything metal from motherboard touching the case[bar the standoffs] and no PSU connectors are touching the case either. PSU is also a good quality its a Corsair RX650.

 

[Lucien Nunes]

Yes, it's normal. There will always be some capacitive leakage from the AC input side of the power supply, for example through the RF interference suppression components. When disconnected from ground, the case of some power supplies (and many electronic appliances) will rise to 100V or more from ground, as the capacitors form a symmetrical divider between line and neutral. The maximum current that passes to the case is typically around 1mA, however for safety such supplies must be grounded. Only class II power supplies (which have a touch leakage of 0.25mA or less) should be operated without a ground connection.