Sparks fly over electric shock dealing Dell laptop Some Dell laptop owners may be in for a shock, but not because of a sudden price crash on its machines. It’s because a number of customers claim they are receiving electric shocks when they touch their laptops. Numerous comments have been posted on a Dell community blog from customers owning Dell XPS M1530 laptops, which they …
Two-pin power supplies often have some sort of capacitive connection between the mains side and the low-voltage side. Typically about 3.3nF, you'll see a hundred microamps alternating current from the low-voltage side to earth. It'll look like about 110V from a 230V supply because usually there's a capacitor from both live and neutral so you have a potential divider in there. Neutral normally sits at earth potential (and is often bonded to it somewhere in the mains system) so you see half the mains volts on the low-voltage side.
Shocking power bricks are quite common and a pain to work with. There's generally a resistor between the mains and low-voltage sides to prevent static build-up (or something).
Bit of a gaffe to specify one for a metal-cased laptop!
Though I once visited an office building where an entire floor was unearthed -- all the PCs and other equipment cases were floating around 100V AC. You only noticed if you touched a computer at the same time as a window frame or other part of the building structure...
Ah, I think (?) that the picture shows that buddy is measuring a DC voltage. If so, then it's not capacitive leakage current from the AC power line.
Perhaps someone could track down a larger copy of the same image to double check that he's measuring 102 volts on the meter's DC scale (more often than not next to the meter's OFF position). The AC scale is normally the next switch position along and indicated with a ~ symbol.
It looks like a big oops by Dell's supplier.
If I use my laptop with it's power supply connected to a 12v>240v car inverter, I get a nasty (NASTY) shock if I touch any metal part of the car connected to the chassis.
Not just the laptop either - same with a portable DVD player (glad I didn't hand that to my daughter !).
Quite right. But the current is determined by the resistance of the body (which varies hugely) and the voltage. And the amount of current it takes varies with your health and so on.
IIRC from my long ago basic training, the "official" current that could be lethal was about 20/30mA, and from this they talked about a minimum voltage that *might* be lethal of about 30VDC, 50VAC.
Of course, if this is just volts due to leakage current in the Y caps, the internal resistance of the EMF (another variable) is likely too high to allow it to supply more than a few milliamps.
But any which way, 100V on a laptop case is a Bad Idea.
It is AC (from the pic)... if you look closely you'll see that the meter just has one dial position for volts and a button to toggle between AC and DC.
In the top right corner of the display, you'll see a frequency reading of 50 cycles (note I'm not saying Hz because I don't know if it does hurtz).
So, unless anyone can show me that it's 50 cycles of DC, I'm going with AC.
Posted as AC just to make the point!
And I was sooo tempted to use the skull and crossbones, or the heart icon, but I thought I'd go with Paris for the usual tingly sensation!
I receive a LOT of Dell spares - recalled hardware and kit that's been swapped out as faulty - and I've noticed an increasing amount of those palm rests recently ( the metallic ones ).
This didn't suprise me too much. The boxes are often full of things like "no power to laptop" and in the box is the power LED, and even worse "red hdd light kept flashing" and the hard drive was enclosed. Dell engineers are even less intelligent than PC World sales staff - so I've little doubt they've had a few reports of the laptops shocking them and then moronically replacing the wristpads. Out of idle interest, I'm going to check the fault reports in some of them next week ;)
I saw this effect several years ago with various metal clad laptops. Some users had felt a current from the case and the devices affected included Apple MacBooks and Panasonic Toughbooks. The culprit seemed to be the switched-mode power supplies. They measured 24V across their output but 50V to 100V with respect to earth. Older types of power supply, which contained a large and heavy transformer, did not have this problem. The manufacturers went to great lengths to reassure people that the effect was not dangerous. I've just measured the output of an Epson power supply for my P4000. Its has the expected 5V DC output but shows 80V AC to earth.
I have an Inspiron 9300 bought back in 2005. Ever since it has shocked in some places. The edge of the screen lid and the outside edge of the USB ports.
It was the inconsistency of the shock/tingling that stopped me from reporting it to Dell. Sometimes it would go weeks without shocking. Plugged into the same power supply, socket everything, then one day there was a reminder POW!... What was weird was if I plugged the same power brick into my newer inspiron 9400, it doesn't shock? So, you have to question why their solution was to replace the bricks
I think Dell could sell it as a feature. Certainly, it wakes you up better than a cup of coffee and as for falling asleep and dribbling on the keyboard, that would be just a death wish...
Incidently, is this the source of the spark for battery fires last year?
The biggest and nastiest one was a cheap USB to IDE adapter from eBay with included power supply. It throws out sparks when you first touch it to a grounded USB port, and makes the stereo on the same circuit carry on a treat too - often causing the USB ports to shutdown and restart themselves. I don't use it now...
.. and then last night I got a belt from my Palm of all things! But this was due to a switch mode power supply gone bad. In this case, the Palm USB cable was connected to a $10 12V USB charger / FM transmitter unit, which in turn was connected to a 12-240V switch mode adapter that originally came with an LED sign from eBay. Having a grounded laptop on my belly when I grabbed the palm just made it more fun!
Strange that these things never seem to trigger earth leakage breakers...
I have a Dell M1330 (very similar model, identical casing to whats shown in the picture).
All this has happened to me! I actually thought the tingling was part of the surface texture, it happened so often.
I've had quite a few electric shocks from it too, but I just put it down to static electricity.
As said above - it could be 1000v, or 100v, what matters is the current that its giving out, not the voltage.
Out of curiosity, I did some tests on this laptop (the M1330) just now, and I don't get any 100v voltages (although I haven't been tingled for a few days now).
My macbook pro has given my hands an interesting tingling feeling since the day I bought it - which stops immediately on disconnecting the PSU. It seems to be much worse if I have an unpowered USB device like a mouse plugged in - presumably this helps to form some kind of contact between the various bits of the highly conductive aluminium chassis.
My theory is that unearthed swtched mode PSUs seem to be the issue here - yes they are suitable for use in just about any country with AC but the earth pin is there for a reason in the UK is it not?
xx
The same thing happens to my new MacBook Pro, I thought it was the poor mains power in outback Aussie, but then I went back home to New Zealand and it is still happening here.
Gentle tingle touching the case, but if I am only touching on a tiny surface area (corner of case on forearm, say) then it feels sharper and more intense, almost painful. Any comments?, is this a feature or a problem? (I once bought an electric lawnmower with a special safety feature. As the salesman explained carefully to me, if I was to run over the electric cable with the mower, this special feature would stop the motor from turning. He just could not get it when I asked If I could have an electric mower instead that did not have this feature, and kept on running after you cut the cable!)
Just spent several hours "downgrading" a Dell XPS M1530 to XP Pro, and it has been shocking.
Every time you touch the bloody thing without grounding yourself, there is a large noticeable shock.
Talk to Dell today about the downgrading (they were useless, couldn't even find information on their own web site about the process) and mentioned the "shock" factor. Support person had no idea what I was talking about.
Maybe they figure anyone who buys a laptop loaded with Vista requires electro shock therapy as they are clearly crazy!
- In order to not affect (i.e. load down) the circuit being measured, voltmeters are very very high impedance. The tiniest parasitic capacitance can result in seemingly lethally high voltages when driving a 10Mohm load. The voltage/current they deliver into a much lower impedant human earth path is closer to mV and uA.
- the real reason this happens is of course the modern, two pin (i.e. no earth connection) 'floating' switch mode power supply has no way to earth the case and protect the user. Should really only be used with plastic cased goods though and ideally a plastic that doesn't hold charge very well.
I have the same problem with my Dell Precision M65 when it's running off the mains. I don't know if the power brick is a two or three pin one and I can't check now, as I left it at home today. I'll have a look tonight and get in touch with Dell to get a three pin one if mine isn't.
"The number of times I've been electrocuted,"
Really? I was under the impression you could only be electrocuted once... you can receive many electric shocks, but actually being KILLED by electricity I'm pretty certain can only be achieved once per person...
http://dictionary.reference.com/browse/electrocuted
My MBP does it too - but only if I have the power adapter plugged in one specific way into the mains. If it happens, I just unplug the adapter, plug it in the other way round (it's a euro 2-pin) and the problem goes away.
My house is old (120yrs) with most of the wiring still the original cloth covered lot and 3-phase coming in, and I'd always assumed it was caused by one of the million electrical gremlins that infest the place.
(ps 120 years is old for South Africa)
rolled back and installed XP on a number of M-1330s and have had a few little zaps in the process.
end users that get them are gits anyway :P so im saying nothing......
@Sarah Millin
for the M-1530/1330 try the US dell site, after speaking to Dell UK about rolling back I got "its not supported" so I googled it myself.
the only thing to keep in mind is before installing xp do the following:
Disable the cacheram device and change the Sata drive to Base mode.
(the AHCI mode would work if you can find AHCI drivers for the system that work in XP, I gave up.)
Apart from that XP runs a dream on the systems.
Dell US have the HD audio drivers & the 8400GS drivers that work flawlessly in XP. UK dell hadnt a clue! If you cant find the 8400 drivers jot down the name of the device in bios and google it, there are working links!
I had the same issue with my apple Ti powerbook... mild tingling on the casing and a proper belter if i wrested my wrists on the carbon surround, especally if it was humid... instantly solved by getting a newer PSU with a metal guide nobble and using the long mains lead, not the cute little stumpy plug adaptor..
:)
... on my Dell Inspirion 8600.
It's not noticeable during normal work, but when I was on the beautiful island of La Palma in December, I noticed a tingling sensation when touching the frame of the screen while plugged-in. The strongest "shock" was touching the shielding of the svga-socket while blindly searching for the usb-slot on the backside. It was quite uncomfortable, but not painful as such.
At this time I was barefoot on the ceramic tiles in the house. Not surprinsingly, it went away when I put my (cork-soled) sandals on (though I thought, the ceramic tiles shouls be pretty good insulators, too).
At that time I thought that maybe some strange wiring in the house was responsible for it, because before and after that holiday I never experienced that sensation again.
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