FR adapter - shocking experience!

Sébastien Lorquet squalyl at
Tue Oct 14 11:50:15 CEST 2008

Just guessing, FR power supplies blocks are really high-tech ones if they
contain a usb-powered 230V power inverter in the same package :-D

to get 5VDC from 230VAC you need at least a transformer and a diode bridge +
low voltage capacitors, or a step-down hasher like desktops/laptops power

but, to get 230VAC from 5VDC, you will first need 5VAC with an oscillator,
then a step-up transformer :)
This is not something you'll find on a standard power supply plug :)
Also, the shock would not be the same if you had been shocked with a
normally operating 230v supply (I mean the amount of energy absorbed by your
body) :)

this is more likely to be a capacitor effect. There are some on the 230VAC
side of all power supplies, to filter EMI.

and a coil cannot store potential, it's a capacitor job :)
a coil regulates spikes et reacts to transient voltages only. for DC
current, a coil is a simple wire.


2008/10/9 Thorben Krueger <thkruege at>

> It might be a case of the transformator working in reverse: A small
> voltage applied to the usb output leads to a high voltage at the
> prongs. This could also be caused by a capacitator on the low voltage
> end, but I am not sure.
> Just guessing here.
> However, if you were to touch the prongs the moment they were out of
> the socket, the coil could still hold some potential to shock you.
> Also just guessing.
> Thorben
> 2008/10/9 Christ van Willegen <cvwillegen at>:
> > Hi,
> >
> > this morning, I pulled the FR adapter out of the (230 VAC) socket, and
> > accidentally touched one of the prongs. I experienced a short shock.
> >
> > Is there a capacitor in there that can do that? It was fully out of
> > the socket when I touched it!
> >
> > Christ van Willegen
> > --
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