Re: [OT] USB, electronics and ground

["Andy Davies" <dajdavies@xxxxxxxxx>]

On 08/09/06, Paul Gale <groups@xxxxxxx> wrote:
>
> Hi Wayne,
>
> Not sure - this PC is a real mess at the moment - refusing to boot
most of
> the time, CMOS settings getting screwed etc - when it does boot, it
crashes
> every now and then. My theory at the moment is that the mainboard is
screwed
> and maybe was caused by dodgy USB power etc?
>
> I got a shock (light tingling) from a USB cable shield yesterday -
> connected to a newish Belkin hub but when I touched it today, it's
fine.
> Maybe I inadvertently was touching the PC case at the time? Kind of
shock
> you get when sometimes touching audio leads whilst holding other
equipment.
>
> Anyone else know what kind of voltage you should expect between
grounds
> like this?
>
> Can I earth the case and any other kit maybe?
>
> What steps should I take to test all the earths - will testing
voltages
> with a meter help?
>
> Paul.


You haven't got a badly wired mains cable somewhere in the mix?

Many years ago when I worked for a VAR there were a stack of machines being
burnt in, when I reached around the back of them I got a shock where my arm
touched two machine - it turned out someone had misswired earth and neutral
in an extension cord!

One thing to try is stick a multimeter between the ground in the case and
the USB cable and see what tha voltage is.

Andy


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