I have various power supplies in the range of 5 V DC to 19 V DC which still have about 60 V AC pollution in their output. This makes me get zaps from the attached devices quite often. Is there a way clean the output? I'm tired of getting zapped.

  • \$\begingroup\$ That sounds like your premises earth isn't wired up properly, or some similar line problem. \$\endgroup\$
    – pjc50
    Jun 8, 2014 at 9:49
  • \$\begingroup\$ Is your AC voltage 120V? \$\endgroup\$
    – Andy aka
    Jun 8, 2014 at 9:50
  • \$\begingroup\$ I'd probably call an electrician on this one. Something to note is that neutral / earth problems can get worse depending on environmental factors such as soil moisture and corrosion of wiring so the annoying zap might not stay that way. \$\endgroup\$
    – PeterJ
    Jun 8, 2014 at 9:57
  • \$\begingroup\$ European network: 240V \$\endgroup\$
    – bot47
    Jun 8, 2014 at 10:40
  • 1
    \$\begingroup\$ How are you measuring the 60VAC - can you show a circuit and indicate the apparatus used for the measurement? \$\endgroup\$
    – Andy aka
    Jun 8, 2014 at 10:45

1 Answer 1


Assuming you have a 120VAC power feed into your premises, half that voltage "can" be seen when you haven't got a proper earth: -


simulate this circuit – Schematic created using CircuitLab

A lot of power supplies have EMI reduction circuits on input and output and these shunt switching noise to the earth line. When you don't have the earth connected properly the 120VAC supply voltage forms a capacitive potential divider with C1 and C2 - the net result is 60V AC on the earth wire and this AC inflicts itself on the DC output via C3 and C4.

EDIT - The OP has said that the incoming AC supply is 240VAC so now to justify 60VAC on the output, it is necessary to look at how this measurement is made. The same basic principle stands - the lack of earth can cause an infliction of input AC power to the output wires via the EMI protection components.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.