I want to ask why I'm getting a mild electric shock when touching the metal parts on my PC (I don't have any rug / carpet in my home), and most PC power supply supplies I have been working on are giving me electric shocks whenever I touch the PSU body or the output.

But recently I have been working on cheap Chinese SMPS from 5 V, 5 A to 12 V, 60 A, and they are not giving me an electric shock (turn it on without Earth / 2 prong cable) when I touch the body nor the GND output. And the last test I have done is a power supply for a claw machine (48 V, 5 A). It does looks like a PSU for a PC (same case) but it's not giving me any electric shock.

I checked with my "line checker" is OK no reverse on line / neutral just doesn't have earth cable (2 prong).

Can it be something wrong with the Y caps?

Or what's the explanation of this? Is it normal for a PC PSU?

And how do I check if the leakage current is fatal, because my current PC is giving me a very mild shock.

  • \$\begingroup\$ Are you by any chance connecting PC with grounded plug to ungrounded outlet? And similar questions get asked here frequently, so have you searched for similar questions if they already provide an answer? \$\endgroup\$
    – Justme
    May 14 at 7:26
  • 1
    \$\begingroup\$ See this answer at EESE, for example. "That is why if you measure the output of a class 2 PSU relative to mains earth with a high impedance meter you will usually see around half the mains voltage." Which is pretty much exactly what I measure on my Microsoft surface book 1. \$\endgroup\$
    – jonk
    May 14 at 8:33
  • \$\begingroup\$ Does this answer your question? What does the Y capacitor in a SMPS do? \$\endgroup\$
    – winny
    May 14 at 10:12
  • \$\begingroup\$ The answers and comments re Y capacitors are almost certainly correct. The supplies that do NOT shock you probably have no y capacitors and may cause interference. \$\endgroup\$
    May 14 at 10:52
  • \$\begingroup\$ @ATCSVOL The supplies that don't shock may still have Y caps and may not emit much interference, but their internal structure may just be more expensive to remove leakage. There are 2-prong ungrounded supplies, 3-prong grounded input supplies that still isolate the output, and 3-prong grounded input supplies with grounded output. 2 prong supplies may or may not shock, and connecting supply with grounded input and output such as desktop PC to ungrounded outlet will definitely shock you. \$\endgroup\$
    – Justme
    May 14 at 11:14


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