In message , Piers Finlayson
writes



On 25/08/2009 09:16, in article
, "D.M.
Procida" wrote:

When plugged into one mains ring in the house, my aluminium MacBook has
a soft 50Hz tingle to it (that can be felt when brushing it lightly with
your skin).

Plugged into another, it doesn't.

The MacBook does not have an earthed connection - only live and neutral
enter the PSU.

What's the likely explanation?

I get this whenever I
- use my MBP on the train and
- plug the power adaptor into the in-seat (table) power and
- rest one arm on the MBP and the other on the (presumably metal, earthed)
arm-rest.

It can actually be quite painful - like a stinging more than a tingling.
This might be because it comes through the underside of my fore-arm which is
more sensitive than fingers or the back of the arm.

I've meant to try using the long power lead with the power supply, instead
of just the stubby plug thing (which doesn't have an earth). I haven't
because I can't find it...

I've also not wanted to use a multimeter on it on the train because of the
strange looks and/or accusations of terrorism which may ensue.

"Don't anyone move - I've got a Fluke, and I know how to use it !"

Don't be such a wuss

--
geoff