In article ,
Piers Finlayson wrote:
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.

You could use a neon screwdriver. Will light up nicely. But neither that
or a DVM tells you much since they draw virtually no current. And you
already know there are volts present. ;-)

--
*The statement below is true.

Dave Plowman London SW
To e-mail, change noise into sound.