Most outlets in my house are non-grounded (line and neutral contacts only). I just bought a Hakko fx-888d soldering station, and immediately noticed that touching the iron-station cable gives the same sensation as when I plug in my aluminium Macbook. This sensation disappears when I unplug both devices. I measured the voltage between the ground (from a grounded outlet in the bathroom) and the Hakko cable; it was about 100...110 V (I used the AC regime of the multimeter).

What causes this voltage? Is it dangerous for me or for electronics?

UPDATE: I live in the Netherlands, where having 2 contact outlet is allowed. The human safety is ensured by RCD = GFCI. The house is not that old and is well wired (with copper) and grounded, where required. While I'd be happy to improve it and rewire the ungrounded outlets, it doesn't make much sense as I am renting.

Also, plug orientation here is arbitrary (plug can be inserted in the outlet in two ways), so the design never relies on which wire is neutral and which one is line.

  • \$\begingroup\$ A duplicate of electronics.stackexchange.com/q/267146/117785 and many other questions about AC-DC converters leakage. \$\endgroup\$ Commented Mar 16, 2019 at 20:18
  • \$\begingroup\$ @Ale..chenski Different device, but same issue. Likely a conventional step-down transformer with poor primary-secondary isolation. Capacitive coupling can be substantial. \$\endgroup\$
    – user105652
    Commented Mar 16, 2019 at 21:02
  • \$\begingroup\$ If your house is old enough to be an ungrounded system, it is possible many of your plugs are wired incorrectly with hot and neutral reversed. For parts like casings that should be attached to ground and nothing else for safety reasons, when they are left floating, they can sometimes be brought to substantial voltages by parasitics. It would be wise to get a plug tester and test all of your plugs, and of course it is unwise to use a device that requires a ground with an ungrounded source. \$\endgroup\$
    – K H
    Commented Mar 16, 2019 at 23:59
  • \$\begingroup\$ This sensation you're describing, can you describe it better? You mention it as if it is normal, but generally speaking, you should feel nothing whatsoever when you plug in a device, Macbook or otherwise. Is the sensation you describe the sensation of getting a 120V shock? If so, cease the activity immediately and troubleshoot your system or if you don't have the necessary skill, hire an electrician. Even if they don't kill you (50-100mA at 120VAC is about right to stop the heart), 120V shocks can cause permanent heart problems and should be avoided. \$\endgroup\$
    – K H
    Commented Mar 17, 2019 at 0:03
  • \$\begingroup\$ Can you also provide a picture of the part of the cable you are referring to? My Hakko uses an insulated cable with the only exposed metal parts being the tip and tip holder. Where is the exposed metal you are measuring voltage to ground from? \$\endgroup\$
    – K H
    Commented Mar 17, 2019 at 0:08

1 Answer 1


Plug config. doesn't really matter in case of AC supply as long as you don't have dual supply systems (in some countries you can get both DC and AC supply on request to your house) .

Having an Earth connection is a good safety measure since the electrical wiring wears over time due to the heat produced in conductor inside and the aging insulation around the wires ,which will start to conduct electricity slowly over time .There is chance that at some point of time the insulation of whole electrical circuitry in your house could fail and can cause electric shock of max. supply voltage while using home appliances due to leaking current .

And also Earthing provides safety for the circuit itself avoiding/delaying possible fire accident due to shorting between the Live and Neutral wores incase of failure of wiring insulation .

Summing it all up ,I'd suggest you to change all your sockets in the house to 3 pin sockets (with dedicated Earth supply I mean) and provide proper earthing and use appliances with earth connection as much as possible .


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