On 24/07/14 22:08, Baron wrote:
aeio prodded the keyboard

On 24/07/14 19:39, whit3rd wrote:
On Thursday, July 24, 2014 10:02:01 AM UTC-7, aeio wrote:
I noticed a tingling from contact with a USB lead of an external
Hard Drive.


Investigating this led to the PSU, the plug of which has a high
voltage on the outer connector compared with house earth. It was
varying between 70 and 110V.

A voltmeter might pick up leakage, but to determine if it's
hazardous, you
need a load. I'd start with AC milliamp scale (try on high amp
scale first, of course)
to test further. It's probably a bad PSU just as you suspect (if
you feel it it's maybe a few milliamps, but microamps might be
acceptable). Connect one probe to ground, the other to the
touchable metal part.

The 'correct' way to test involves a dive into a variety of
national and international standards. One half milliamp into 1500
ohms parallel with 0.15 uF, is a typical 'safe' threshold.

slowly going up and down between 0 and .005 milliamps - on a cheap
multimeter.

Is it worth trying it with a capacitor?

A reading that small could just as well be leakage. Are you sure that
should be milliampere and not amps ? ie 5 ma.

Yes - 0.005 mA. That is on the 2mA scale. There is nothing showing on
the higher scales and nothing on the AC scale.