🚀 go-pugleaf

Sylvia Else wrote:

> J.A. Legris wrote:
>> On Mar 8, 10:35 am, Sylvia Else <syl...@not.at.this.address> wrote:
>>> Sylvia Else wrote:
>>>> I've recently bought a D-Link DIR-300 wireless router. While
>>>> disconnecting its power supply from it, I got a tingling sensation
>>>> when I touched the plug (to be clear, I'm talking about the 5V DC
>>>> plug, not the mains plug).
>>>> An AVO meter shows about 90V AC to earth from either side of the 5V
>>>> plug. Short circuit current to earth is about 0.1mA.
>>>> Still, I thought these things were meant to be completely isolated.
>>>> Has there been a change of approach?
>>>> Sylvia.
>>> Apparently it's normal, and is related to RFI suppression.
>>>
>>> Sylvia.
>> 
>> Just think, the only thing between you and the great beyond is a thin
>> layer of ceramic material, possibly contaminated with who-knows-what,
>> bearing a certification logo of dubious authenticity. It's time to
>> invest in some rubber-soled slippers.
> 
> It's certainly not a happy thought. I will be treating the low voltage
> side of such power supplies with more respect from now on.
> 
> BTW, I tried the same tests with the power supply for my cable modem.
> It showed higher voltages, but lower current.
> 
> But immediately after I'd unplugged it from the mains, I happened to
> touch the mains plug pins with the palm of my hand, and got a
> significant shock off it. Reverse leakage through the rectifiers? But
> why should there even be enough to feel?
> 
> Sylvia.

That is also quite normal !  There is one or more capacitors across the
supply pins.  They can be left in a charged state at the instant you
pull the plug.

The voltage you measured on the output side was simply due to the
leakage capacitance of the transformer or if a switch mode psu the
capacitors on the supply side having a connection to the common rail.

-- 
Best Regards:
                     Baron.