Yes well, the bodger who fitted the kitchen was not an electrician, it
turned out just a kitchen fitter trying to save time and extra money in that
out of sight out of mind way some people have.
The older TVs of course had the chassis at half mains voltage and the
aerial socket was supposed to contain isolating capacitors, but even those
can get charged up to high voltages and also you can get leaky capacitors
after some time and this practice luckily has now almost stopped, in favour
of the switch mode psu which is then supposedly isolated by its much
smaller transformer working at the higher frequencies. Having said that I
have seen cheap Chinese wall warts actually come apart when you try to pull
them out of a socket leaving live ends of the mains pins bare inside. Not a
good design.
Brian

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The Sofa of Brian Gaff...

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"NY" wrote in message
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"Brian Gaff (Sofa)" wrote in message
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Yes that would certainly do it. I am very sensitive to that
electrostatic Talking of real life sad cases though, the daughter of an
MP had just had a new kitchen fitted and was trying to get something out
of a cupboard and touched a securing screw with one hand while steadying
herself on the washing machine with the other. She was killed instantly
and the kitchen fitter was convicted of involuntary manslaughter. He had
basically joined a number of wires up inside a wall cavity, and not
filled in the hole merely screwed the cabinet over the top, One of the
screws in the back had just caught a live wire and was thus live and the
washing machine was earthed. The report did not go into too many details,
but apparently she was alone her heart stopped and she fell off her
kickstep and hit her head on some appliance.

That's nasty. And such a stupid mistake for the electrician to make.

Earthed appliances can be more trouble that they are worth if you happen
to touch an appliance that is live.

I got a nasty jolt when I unplugged a TV aerial cable from a USB DVB tuner
connected to my PC. I had the metal aerial plug in one hand and was
holding the earthed case of the PC with the other hand. As soon as the
plug was no longer in contact with the earthed PC, I got about 100 V
across me. Probably very low current, but it was enough to hurt for a few
minutes afterwards. Another leg of the TV aerial was plugged into my TV
(which was off but plugged in) and from there audio and SCART cables went
to a VCR, an OnDigital box and my hifi. One of those was evidently to
blame. Having disconnected everything in turn, with a voltmeter across the
aerial plug and mains earth, I narrowed it down to the TV. It was putting
out about 300 V as measured with a high-resistance voltmeter which went
down to about 100 V when I put a human-sized resistor (I measured my
across-the-chest resistance as about 200 K ohms) in parallel to simulate
me touching aerial and earth. So there was a large internal resistance,
but not large enough to prevent a noticeable jolt.

After that I rigged up a wire from mains earth to the aerial amplifier's
screen connection, to make sure everything was earthed. All it needed was
one earthed appliance (the PC) and everything was OK, which is why I'd
never noticed the problem before, but as soon as that earthed connection
was removed, everything was "semi-live". Sod's Law: everything else was
double-insulated and so not earthed. Probably to avoid hum loops as much
as to avoid needing a three-pin mains lead.


I've only had a "proper" mains shock twice in my life. Once when I made
the elementary mistake of working on a tape recorder that was turned off
(so everything downstream of the mains switch was safe), forgetting that
the input terminals to the switch were live... This was in the old days of
a fuse box that only contained (wire) fuses, with no earth-leakage RCD. I
still have two marks on my finger where it touched the soldered switch
pins for the live and neutral feed: it looks like a snake bite ;-)


The second time was equally silly. I was changing a lot of GU10 light
fittings which had Philips Hue bulbs in them - the type of bulb is
important, because these can be turned off with the mains still live
(there is a switch inside the bulb which is controlled by a phone app).
Each time I did a few more fittings, I turned off the wall switch and also
the circuit breaker for the lighting circuit. Except for one set, when I
made the stupid mistake of thinking that the bulbs were not lit, therefore
the power was off at least at the wall switch. Wrong! On that occasion the
house was protected with an RCD, which did its job and tripped very
quickly: I know that because it also killed the table lamp that I was
using for illumination while the ceiling lights were supposedly off.

The second shock was much less sever that the first one, probably because
of the RCD, so I didn't have to pull my hand away.