Beware also that the isolated ones often have a high leakage current
from AC ground to the output. That is to say, if you take a high
impedance meter (in AC volts mode) and measure from the DC output
(either side, + or -) to AC ground you will typically see almost full
line voltage there. If you measure the available AC current between
this source and line ground, you may get as much as a few milliamps. I
have definitely had ones which I could feel if I touched the output
and was also touching a metal frame which was grounded.

This is why they always stress that medical grade isolation (uses an
electrostatic shield between transformer pri and sec) is needed in
equipment which is meant to be in direct electrical contact with a
person.

Sean



On Tue, Oct 5, 2010 at 3:35 PM, Bob Blick <bobblick@ftml.net> wrote:
>
> On Tue, 5 Oct 2010 16:22:56 -0300, "John Coppens" said:
>
>> Wow... Are there really wall-warts that _are_ connected somehow to the
>> AC input? That puts a new perspective on 'warts'.
>
> Three-prong ones are obvious, but also some two prong ones "intended for
> radio or television receiving equipment" have a capacitor and resistor
> from input to output.
>
> Cheerful regards,
>
> Bob
>
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