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?
Daniele
Similar on my laptop, I notice it more when I'm in contact with earthed metal (e.g. I've rested the laptop on a short 19" rack and bridge between the rack and laptop with my forearm/wrist).
Could it simply be due to the different rings being in different locations and having different floor coverings, therefore *you* are better earthed (or insulated) when using it on one ring compared to the other?
Have you checked only with one socket (oe double socket if that's the case) on each ring?
Nothing springs immediately to mind other than to ask, have you checked the socket is wired correctly?
This is normal for metal-cased laptops, as they are not double- insulated. The tingle you feel is leakage current through the power supply capacitors. This should go away if you use the full mains lead instead of the plastic 3-pin adaptor, as the former is has a proper earth connection to the supply).
If you measure the potential of the case with respect to earth, using a high-impedance multimeter, you'll see that your laptop is at ~120V. This is not a fault.
Dave
There are commonly high value resistors between what is effectively mains and the casing of such devices for RFI suppression purposes. And you can feel a slight tingle from these under certain circumstances. Perfectly safe, though.
I can't think why one ring over another would make any difference - more likely the local conditions in the room. Although you could check there isn't a neutral line reversal on the socket using one of those plug in testers.
If it really annoys no reason you couldn't earth the casing.
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.
Its statements like that , that make you know that Al Qaeda has in fact succeeded.
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. ;-)
If you put a voltmeter across the earth and neutral connections you may find a fairly high voltage exists between them.
One of my sockets has 110 volts across those wires. It varies on other sockets down to a few volts.
I noticed it when I unplugged my tv aerial and rested my hand on a computer case while doing it. It frightened me out of my already depleted wits.
You can blow the main trip if you short circuit those wires on a socket or light fitting, even when the live for the circuit is disconnected at the CU.
The opinion in here was that some equipment that does not use mains transformers, (TVs, computers), sets up this voltage in the earth and neutral wires. The reason that it appears on one socket and not another is that it does not travel far from source due to being very weak.
If you have the slightest doubt get it examined by an electrician to put your mind at rest.
"D.M. Procida" wrote in message news:1j4zyvw.feuuhi1bzvqbjN% snipped-for-privacy@apple-juice.co.uk...
I'd say on that particular mains socket the 'live' and 'neutral' pins are connected the wrong way round. The (normal nowadays) tingle is due to current leakage through a small EMC filtering capacitor specifically fitted ACROSS! the supposed safety isolation barrier of the switched mode power transformer. These mains rated EMC capacitors seem fitted to all SMPS beyond a few watts capacity and are the only viable, available means to allow passing the EMC type tests.
The consequence is to allow mains to leak through to your equipment and anything else connected to it. Hum loops and equipment failures are common because of this. Apparently this mains leakeage is safe!. What happens when a young kid sat on a nice earthplane kitchen floor sucks on one of the outlet connectors?. Seems outrageous that elf and safety haven't outright banned the sodding things. The elephant sits slap bang in the middle of the room yet remains invisible to those paid to protect us.
In article , Dave Plowman (News) writes
ITYM capacitors, and low value.
You must have a problem somewhere. This house hasn't got PME, but the voltage between them measures about 350 mV.
snipped-for-privacy@blueyonder.co.uk presented the following explanation :
There might be a few volts, maybe 20 between N and E.
There should be no large variation when checked between the N & E of one circuit and the N & E of another. The actual voltage can wonder about a bit though due to various factors. I would be quite concerned if I saw 110v.
Sounds like the Earth on the affected circuit has become open-circuit from the Consumer Unit, and another appliance on the same circuit with normal capacitive filtering is bringing the now-floating 'earth' up to
1/2 mains potential.In message , Piers Finlayson writes
"Don't anyone move - I've got a Fluke, and I know how to use it !"
Don't be such a wuss
Being an electrician on a train has a historially high mortality rate...
They can float at about half mains potential (but with a high source impedence) due to the lack of an earth, enough to feel but not to kill unless in a special location.
Exactly! The risk of terrorism is slight. Very much less than other causes such as RTAs.
If it's more than 20 in normal running I'd be worried that it would be too high under fault conditions (>50v).
Non earthed appliances can have exposed connections at 120v due to mains filtering. TV aerial sockets are usually so, and give a (non-lethal -- unless it makes you fall off the roof) tingle.
TBH I'm more worried about looking like a weirdo than a terrorist. But perhaps it's too late for that ...
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