My computer was shut down and the power supply switch was set to O, but the power cable was still plugged into the wall. When I reached behind the case and touched the PSU's metal ventilation area, I felt a small electric shock. At the same time, the motherboard's standby lights came on. I then switched the PSU on and started the computer; it booted into the BIOS and Windows normally, with no smoke, burning smell, strange noises, or visible sparks. I shut it down shortly afterward, switched the PSU off again, and unplugged it. Could this be caused by a grounding problem or harmless leakage, and is it safe to keep using the computer?
3 Answers
The motherboard lights coming on while the PSU switch is off is normal if the power cable is still connected; standby power can remain available. However, feeling a shock from the case is not something to ignore. Test the outlet and power cable, and if the grounding is good, have the PSU or the computer inspected or replace the PSU. Avoid touching exposed metal while it’s plugged in.
The PSU’s brand and 750 W rating don’t determine whether this is safe. Since the case gave you an actual shock, unplug it and troubleshoot the wall outlet, grounding, and PSU rather than assuming it’s harmless leakage. A brief successful boot doesn’t prove the electrical protection is working properly.
First check whether the wall outlet has a working earth/ground connection. A missing or faulty ground can let the metal case sit at a small voltage and cause a tingle or shock. An inexpensive outlet tester can help identify wiring problems, but it cannot replace an electrician for a serious fault. Don’t keep using the PC if you feel another shock.
I usually switch it off when I’m asleep or when the computer is shut down, but I’ll check the outlet grounding before using it again.