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Dell Laptops Have Shocking New Problem 475

Posted by CmdrTaco
from the jolt-of-reality dept.
dapsychous writes "A friend of one of my coworkers has noticed a problem in Dell notebook computers (also covered in this engadget article about a problem that has been popping up lately in Dell 17" notebook computers). It seems that these computers are putting out between 19 and 139 (65 according to article, 139 according to him) volts of AC power as measured from any chassis screw vs. earth ground. This has led to several problems including fried ram, blown video circuits, and a stout zap on his left hand. According to him, Dell has tried to keep him quiet about the problem and has even gone so far as to have him banned from a few websites, and threatened him with legal action if he tells people about the problem."
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Dell Laptops Have Shocking New Problem

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  • Only in America! (Score:5, Informative)

    by aslate (675607) <planetexpress@NospAM.gmail.com> on Wednesday February 07, 2007 @12:30PM (#17921962) Homepage
    Okay, not really, but shouldn't happen in the UK. According to the article:

    "The latest word is that VG's own problems were solved by springing for a three-pronged grounded power adapter"

    You can't get a non-earthed plug in the UK, the earth pin is physically required to open the plug socket. This can be a dummy pin, but you're only able to do that if the unit itself is double-insulated.
  • Re:Oh shit. (Score:2, Informative)

    by FudRucker (866063) on Wednesday February 07, 2007 @12:34PM (#17922024)
    get a volt meter and check for voltages between a chassi screw and earth ground, it will most likely be DC current...
  • Watch the ESD (Score:5, Informative)

    by Whip-hero (308110) on Wednesday February 07, 2007 @12:41PM (#17922140) Homepage
    For a while, I thought I had a similar problem with both my new Dell laptop, and an old dumpster-diver I had before that. I was getting shocked occasionally when I touched the machines. I initially blamed it on poorly grounded wiring in my house (a rental), until I realized that the problem was electro-static discharge build up from sitting on my Durapella couch.

    I worked it out recently when cold winter temperatures drove the humidity way down. Whenever I got up from the couch I would feel the charge build up, then I would inadvertently discharge myself of a light switch, a metal corner post in the drywall, or worse, on some home electronics. After I accidentally blew out the panel of buttons on a DVD player, I did some experiments. By rubbing my hand on the couch cushions for a few seconds, then using a piece of metal held in my hand (less painful that way) to discharge myself to ground, I found I could jump a spark 2 cm or more. Sometimes, I can get multiple sparks on one charge.

    It's kind of cool, if you know to expect it. And, the remote still works for the DVD player...
  • by Buran (150348) on Wednesday February 07, 2007 @12:44PM (#17922210)
    "Dell has tried to keep him quiet about the problem and has even gone so far as to have him banned from a few websites, and threatened him with legal action if he tells people about the problem."

    On what grounds would this be a valid case? Once you sell something to someone that they own (not license), you cannot tell them what they can and cannot do with it so long as you do not cross any other lines and violate someone's privacy (which is why I suppose selling stuff you bought at auction from a storage company is illegal -- although I think most of what those guys did was OK, and the judge overreached). So this guy has every right to say "My computer shocks me, here's what kind of machine it is" because it's not slander, it's the truth.

    Seems to me like this guy can file under anti-SLAPP rules, can't he? This company is trying to shut up someone who is exposing their mistakes -- and yes, it is a valid complaint (why wasn't he given a grounded power supply when it is known that failing to ground electronic devices can shock users?) and yes he has the right to be publicly heard if he wishes to. No one has the right to not be offended by what he has to say.
  • by Radon360 (951529) on Wednesday February 07, 2007 @12:47PM (#17922240)

    You are forgetting about the LCD screen backlight, which is powered from a stepped-up AC supply in the notebook. My guess is that this supply is shorting out to the notebook chasis, perhaps in the screen hinge, causing this problem.

  • by Rob the Bold (788862) on Wednesday February 07, 2007 @12:49PM (#17922260)

    Dry air == lots of static electricity.

    But this guy says he measured his voltage with the multimeter on AC. Static electricity is the buildup of charge on something capacitive (like you and me) and would be measured as DC. That is, if you could measure it at all, since we make pretty bad capacitors and any ordinary multimeter would quickly drain the charge away.

  • by Alioth (221270) <no@spam> on Wednesday February 07, 2007 @12:50PM (#17922278) Journal
    The LCD backlight - typically runs somewhere in the region of 150V ac. There will be an inverter in the laptop to produce this voltage.
  • by Animats (122034) on Wednesday February 07, 2007 @12:54PM (#17922322) Homepage

    I know my house was built a long long time ago (1951) and the upstairs, while someone put in grounded outlets, it doesn't physically have the ground hooked up - due to the wiring used at the time of it being built.

    That's an electrical code violation. If you have to have a 3-prong outlet on a 2-wire circuit, you must use a GFCI outlet, which gives you electric shock protection. That's allowed by the US National Electrical Code. The outlet plate should then be marked "Isolated Ground". This warns people that plugging in a computer there may have problems, because it can't dump static and noise into protective ground as usual.

    If you're going to wire up power, read a manual on how to do it. It's not rocket science, but there are very specific rules and screwing up is dangerous.

  • by Laoping (398603) on Wednesday February 07, 2007 @01:02PM (#17922480)
    One thing I forgot to point out. I have a 15 inch Dell, and I get shocked. So the issue is not just with the 17 inch model.
  • Re:fix? (Score:3, Informative)

    by Vihai (668734) on Wednesday February 07, 2007 @01:06PM (#17922518) Homepage

    I'm sorry to contradict you but most laptop power supplies are not doubly insulated because the laptop itself is not doubly insulated and you really need to have it grounded in case a fault in the power supply transformer leads mains voltage to the laptop's ground.

    If you disconnect the ground or your wiring doesn't have the ground, the EMI filter capacitors will bring mains voltage (albeit with a fairly big impedance) on the laptop's ground. It is not dangerous, but it may create some problem when the laptop is connected to other devices.

    The guy should simply ground his laptop power supply.
  • by Animats (122034) on Wednesday February 07, 2007 @01:09PM (#17922580) Homepage

    The article is vague. It's not even clear if the problem occurs when the laptop is not plugged into the charger. The power supply for some backlights can produce over 100v, so there is a potential shock source even on battery power.

    If the problem is related to the charger power supply, that's a clear safety hazard. Check for a UL logo, and go to the UL web site [ul.org] to check on whether the power supply actually has approval. If the power supply is made in China, it must have a hologram UL sticker with the UL approval number. There are power supplies out there with forged UL approvals, and UL is trying to crack down. (Those are the power supplies that fail in power supply tests on PC websites. UL tests them loaded up to their rated value and runs them for hours at full load, so the UL logo means it really can deliver whatever power it's supposed to deliver.)

  • 37VAC on 15" Dell (Score:2, Informative)

    by BennyB2k4 (799512) on Wednesday February 07, 2007 @01:15PM (#17922680)
    I just measured 36.8VAC @ 60Hz between a chassis screw and plug ground on a Dell Inspiron 15" Latitude D820. Perhaps I'll put it on the scope after lunch. I wonder if it will grill my sandwich?
  • by arodland (127775) on Wednesday February 07, 2007 @01:17PM (#17922712)
    Pretty easily, when it's full of voltage converters, and a high-voltage inverter to run the LCD backlight,
  • by Bassman59 (519820) <andy@latke . n et> on Wednesday February 07, 2007 @01:18PM (#17922720) Homepage

    How does a computer that runs off a DC wall-wart get you an AC current?
    The wall-wart converts AC to DC, and if it's broken, the chassis of the laptop might float with respect to the mains ground. And you'd measure that with an AC voltmeter.
  • Re:Only in America! (Score:3, Informative)

    by johnw (3725) on Wednesday February 07, 2007 @01:20PM (#17922748)

    Several times between 1986 and 2002. Maybe central London is also different from the rest of the country since you have more unrenovated old buildings. I know my friend's apartment still had quite a few of the round-pin sockets, among other places that I saw them.
    Round-pin plugs and sockets came in 3 sizes (rated 15A, 5A and 2A) and disappeared from general use in the early 1960s. They are retained for a few specialist purposes.

    1) Theatre lights use them for the simple reason that they don't have a fuse in each plug. Every time a bulb blows it takes the fuse out with it and the last thing you want to do is crawl around the lighting bars looking for a blown fuse. Instead each circuit has a fuse (or nowadays a circuit breaker) back at the dimmer rack. These are the large - 15A - size.

    2) Navy ships seem to use them too - I presume for the same reason.

    3) Sometimes houses have some of the 2A ones (very small) wired to light switches. You can thus have the room lit by table lights or free standing lights, but still have them controlled from a switch by the door rather than having to go around the room turning them all on and off.

    You won't however find any round-pin sockets for general distribution purposes in any UK residence these days - central London or not. The last time they would have been installed would have been in the 1950s, and they'd long ago have been replaced by now.

    John
  • Verified (Score:5, Informative)

    by mrfunnypants (107364) on Wednesday February 07, 2007 @01:28PM (#17922856)
    I just checked all the Dell laptops our company owns, about 10 of them (E1505 and E1705 models). All of them are producing around 3-5 Volts of AC off the screws. In fact the one producing the highest voltage is currently on a service call as the system has stopped working.

    I am currently in contact with Dell about this issue and I am being informed they are letting the engineers know of the issue and hope to have a resolution soon.

    The funniest thing I have read regarding this was a post in notebookforums from aindfan:

    "I took my E1705 up to the Senior Design EE lab here. The two seniors that were there glanced over at my oscilloscope and realized what was going on, most likely assuming that I did not ground properly. When we took it over to the new, more advanced scope, the measurements reported were of a 60Hz periodic function with a peak-to-peak voltage of ~150V.

    Being curious EE's, the next natural step that the seniors suggested was to see if we could pull any current out of the screws. A few moments later, we had a circuit with a laptop screw connecting to an LED in series with a 1K Ohm resistor connected to the ground node of a power supply (connected directly to the ground of a wall socket). I am happy to report that the LED turned on and there was a measured current of about 1.4 (mille or micro, I forget which) Amps flowing from the screw to the resistor.

    Remember, folks, there will never be current flowing out of the laptop without a load attached to the screws. So don't hook up any 1 Ohm resistors if this is happening to your laptop, you might fry a few things (due to the large current, remember V=IR).

    I'm opening up a Dell chat now to see about getting this resolved.

    Thanks for starting this thread ViriiGuy. It was quite interesting to play around with the testing for this.

    EDIT: When I asked the dell chat support tech if she could send a 3 pronged power adapter (after I explained the issue), she replied "I cannot do that.""

    Good stuff.
  • Re:Oh shit. (Score:5, Informative)

    by skiingyac (262641) on Wednesday February 07, 2007 @01:30PM (#17922872)
    Rubbermaid.

    Called them up twice because one of their guaranteed for life tupperware container cracked in my dish washer on 2 separate occasions (similar size/type). They apologized, suggested putting them on the upper dishwasher rack to reduce the chance of this happening, and sent me a coupon good on anything rubbermaid up to the value of the thing that broke. I asked how I needed to send in the broken container (which their warranty terms say you have to do), and they said I didn't have to because they trusted that I was telling the truth.

    Otherwise, never had a problem with any of their stuff and the only remotely bad thing that I know of that they did was try to get retirees of a company they bought to pay $40/mo for health insurance.
  • by drinkypoo (153816) <martin.espinoza@gmail.com> on Wednesday February 07, 2007 @01:38PM (#17922974) Homepage Journal

    The article is vague. It's not even clear if the problem occurs when the laptop is not plugged into the charger. The power supply for some backlights can produce over 100v, so there is a potential shock source even on battery power.

    The typical modern CCFL backlight requires 1200V to start up and runs on 400V. The amperage is fairly low.

  • Re:Non-repro? (Score:4, Informative)

    by bladesjester (774793) <{slashdot} {at} {jameshollingshead.com}> on Wednesday February 07, 2007 @01:41PM (#17923032) Homepage Journal
    I had the same problem. Chances are your laptop is overheating. Get a fan pad. They're powered off of one of your usb ports and keep your machine a lot cooler.

    I recomment Vantec's LapCool series, and at about $25 they won't break your wallet.
  • Re:Non-repro? (Score:3, Informative)

    by trianglman (1024223) on Wednesday February 07, 2007 @01:48PM (#17923124) Journal
    RTFA (I know, its Slashdot, but still) The article specifically mentions that his wiring is tested regularly and the problem is not in that.
  • Re:Only in America! (Score:4, Informative)

    by Weedlekin (836313) on Wednesday February 07, 2007 @01:59PM (#17923272)
    "Aren't there around 3 types of socket in common use? The tank-like giant socket with three rectangular pins."

    That's the BS 1363, which was standardised as an electrical appliance connector in 1962. It contains an integral fuse which can be replaced without opening the plug itself, is rated for 13 amps, and is considered by many engineers to be one of the best designed and safest domestic plugs in the world. Most appliances sold in the UK during the last couple of decades have one of these fitted (nowadays usually directly moulded to the cable).

    "The socket with three round pins (possibly in two different sizes!)"

    They're the older BS 546 type which was originally available in 2 amp (small) and 5 amp (bigger) variants. It's rare to see them as standard electrical appliance connectors in the UK nowadays even in old houses, because they've mostly been replaced by BS 1363 types, but they're sometimes used today for centrally switched domestic lighting circuits, where a fused plug can be inconvenient due to being hard to reach and therefore check / change.

    "Also an "electric razor socket" putting out 115V in a bathroom"

    You mostly only find these (BS 4573) in hotels and guest houses so that foreigners can plug stuff in without it blowing up. British consumer and safety laws don't allow 115v items to be sold in general retail (although some specialist devices are available for particular applications), so it's very unusual indeed to find one of these in a domestic setting, especially as they're commonly in bathrooms where UK law requires that sockets of this type be connected to an isolation transformer, thus making them rather expensive. A lot of domestic bathrooms do have two pin shaver connectors, but they're usually C17/E "Europlugs" that only output a standard British 240V/50Hz rather than the BS 4573 type.
  • Re:Verified (Score:3, Informative)

    by mrfunnypants (107364) on Wednesday February 07, 2007 @02:02PM (#17923328)
    I have been testing this issue more while on hold with Dell's technical support.

    If I disconnect the AC adapter and test the screws again the voltage essentially disappears. From what I have read on other forums the issue seems to be that the AC adapters supplied by Dell are two pronged, no ground, and if you use a three pronged adapter the issue is nonexistent. From my test this seems to support this conclusion.

    If you have a E1705 or E1505 I would suggest calling Dell and discussing this with them as I have a feeling if properly tested all newer laptops are having this issue. (Please remember I have only tested 10 laptops which is not a large sample size.)
  • Re:Oh shit. (Score:1, Informative)

    by Anonymous Coward on Wednesday February 07, 2007 @02:20PM (#17923590)
    I don't know where to start with your comment.

    When you use a meter to measure current and power, you select what you want to read, then attach and read it. In this case, it would be either AC or DC voltage or AC or DC current, that is four seperate things and requires moving the selector switch between the seelction to read it.

    You can have AC and DC voltage traveling between two points on the same wire. With the AC and DC voltages, you would natually have some type of current flow for each of them as well.

    Another issue, if you want to measure current with a standard multipupose meter, current will pass through the meter. You could have NO actual current flow at all but when you hook up the meter, have lots of current flow because the meter is acting as a wire. Try it sometime, place your meter on AC current and attach it to the two prongs on an AC outlet. I bet it will make a loud noise, read the maximum amount of current it can display and then read zero current. The noise will be either the meter breaking, the internal fuse blowing, or a spark or a combination of all of them. The maximum current reading will be just before the fuse blows and the zero reading will be after you broke the meter or blew the internal fuse (Disclaimer: please don't really try this, it is dangerous). The other method of measing current is a "clamp" meter which measures the current flowing through a wire via the magnetic field. Well, if you have no wire to clamp the probe around, what are you going to measure?

    So... your comment about messuring the current does not make any sense at all. You would want to read voltage potential between those two points and that is what the person did do. He measured the AC voltage and told us it was between 19VAC and some higher number. You responded with I bet it is DC? How do you think the messured 19-120VAC is going to be DC voltage or how would that AC voltage make DC current? Do you see how your comment makes no sense at all?
  • Re:Only in America! (Score:3, Informative)

    by RandomJoe (814420) on Wednesday February 07, 2007 @02:33PM (#17923768)
    All the D-series laptops we got at my office in the past 6-8 months or so (as well as the docking stations) have 2-prong cords. I got mine May last year and it had grounded plugs, but was about the last one... Other than the AC cord, there doesn't appear to be any significant difference.
  • Re:IMPOSSIBLE!!! (Score:2, Informative)

    by Electronics Guy (1061164) on Wednesday February 07, 2007 @02:36PM (#17923810)
    That is true, and LCD Display is powered by a high-voltage source, high voltage being around 30vDC, NOT A/C!! I know my electronics b/c I have spent pretty much my entire life dealing with them in ways most people are afraid of. I have always carried a multimeter in my back pocket, and yes, high voltage for DC circuits in electronics, such as computers, is around 30v DC and any more than that would cause severe damage to the electronic circuits that drive the devices. Not to mention that I am not wrong, NOR am I "plain dumb" such as yourself. Even if it were to be running on ANY form of high-voltage circuit, the current in the circuit would be so minimal that it wouldn't do anything more that give you a little "buzz."
  • Re:Excuse me? (Score:3, Informative)

    by lukas84 (912874) on Wednesday February 07, 2007 @02:37PM (#17923816) Homepage
    I didn't RTFA, but in countries like Switzerland, we have regular wiretestings. You're obligated to do them, if you don't do them, you will get disconnected from the Grid.
  • by Ancient_Hacker (751168) on Wednesday February 07, 2007 @02:38PM (#17923844)
    Every power supply is required to have two capacitors from each side of the power line to ground, and another capacitor from ground to output ground.

    Now if you hook a typical $4.99 digital voltmeter from Harbor Freight, the input impedance of the voltmeter, combined with these capacitors, will indicate anything from zero to 377 volts.

    And if you rub your cat, the voltage could go much higher!

    As you bright folks out there may be guessing, it's not the voltage so much that is the problem, it's the current. And the current is miniscule, microamps.

    So no conspiracy here, move along, etc....

  • Re:Excuse me? (Score:3, Informative)

    by trianglman (1024223) on Wednesday February 07, 2007 @02:51PM (#17924036) Journal

    The quote from the article is:

    All 3 of [the laptops] have the exact same problem. I know it is not my electrical system, as this is a PC repair shop and we have everything tested and certified regularly.
  • Re:Non-repro? (Score:3, Informative)

    by dgatwood (11270) on Wednesday February 07, 2007 @03:02PM (#17924170) Journal

    Realistically, I can't see why you'd ever have the voltages claimed by this article inside a laptop. Laptop supplies are usually 24-ish volts. Anybody reporting numbers higher than that probably has something else wrong, like an inverter power cable that is being pinched by a hinge or something. Either way, at the current levels we're talking about, it should be pretty harmless, if a little uncomfortable. However, Dell still should fix their supply design for other reasons.

    I was helping someone on one of a recording bulletin board solve a grounding problem with an Inspiron laptop just last week. In that case, the person was getting what appeared to be charge circuit noise in the audio output when the laptop was charging and connected to a properly grounded set of powered speakers. Why? Because the Dell power supply uses a two-prong cord, so the laptop is one giant floating ground, or as it is more commonly known, an antenna. :-) For that reason alone, Dell should correct their prong deficiency.

    But yes, the shock would suck, too.

  • Re:Non-repro? (Score:4, Informative)

    by Vreejack (68778) on Wednesday February 07, 2007 @03:05PM (#17924210)
    Actually that won't happen. If the laptop is running on batteries there won't be a closed loop through the bath water. The current has to flow from one pole of the battery through your body and back to the other end of the battery, preferrably after having the voltage multiplied a few times. If you are getting shocked from a self-powered laptop the route is probably from one part of the chassis to another, so grounding your feet in bath water won't make much of a difference.
  • by Cervantes (612861) on Wednesday February 07, 2007 @03:30PM (#17924602) Journal
    We're mandated on Dells where I work. An incredibly stupid user (the kind who gives you a headache as soon as you see her number on the caller ID) sent me her laptop once, saying it was doing "funny things". I was rushed, but I tossed it on my desk, grabbed the power cord, plugged it in ... and immediately got a huge shock on my leg where the brick (which sits in the middle of the cord on Dells) was touching. Enough to make me curse loudly and jump, and leave a mark on my leg.

    Turns out the idiot user had mistreated her power cord, to the point where the wiring going into the cord had worn away... the covering, the insulation, down to bare copper. In her infinite stupidity, she saw this, and covered it with a bit of black hockey tape, apparently knowing about the magic fix-it properties of hockey tape when it comes to consumer electronics. Of course, even the job she did of taping it up was crap, the tape was coming off, things were shorting out, and in my case, zapping away.

    How this woman wasn't reprimanded for extreme stupidity, I'll never know. My employers relative lack of response or sympathy certainly told me a lot about my then-boss.

    That's what I think of when I think Dell and shock.
  • by netsfr (839855) on Wednesday February 07, 2007 @03:42PM (#17924744)
    I just had my video card replaced under warranty by Dell after it started to have problems @ 8 months old. The biggest issues I have with Dell is the over 2 hour tech support phone call, to tell them that it was a video card issue, not a windows driver issue when the text displayed in BIOS is garbled. It was amazing the things the tech support guy wanted me to try to figure out if it was the display or the graphics card, like wanting me to go find a magnet so I can wave it over the keyboard... I had to keep fighting the "reload windows" path by telling them that the graphics hardware was bad when their BIOS logo on boot is corrupted, and that fixing anything in windows, Linux, BIOS or anything on a CD would not help. Half of the call was strange questions injected during the debuggin session about "how" I use my laptop trying to figure out if I abuse it. Its basically a gaming desktop for me so it looks brand new and has sat on the desk never handled for months. Truly amazing (and frustrating).
  • by ThePowerGorilla (930379) on Wednesday February 07, 2007 @03:48PM (#17924840)
    The issue is that a laptop shouldn't be leaking any current. None.

    Almost all devices which utilize wall-operated power supplies can have leakage current associated with them.

    A circuit designed as you suggested is a potential lawsuit - if a capacitor shorts, the user gets full line current

    Dropping a laptop on your toe is a potential lawsuit. The capacitors mentioned by the other poster are called X and Y caps. Any transformer-coupled switching power supply will electrostatically couple energy from the primary of the transformer, to the secondary. This energy can result in lots of signal integrity related problems in the connected equipment, as well as EMI/EMC issues. In order to minimize these problems, a ceramic capacitor is connected from one leg of the primary, to one leg of the seconday. It gives a return path to the coupled energy. These capacitors have a UL listing that is separate from that of the power supply. They don't fail. Ever. They have a rating of almost 4kV, and are hi-pot tested to that at the factory.

    I think it would be nice if the slashdot crowd learned more about the toys we hold so dear. It's worth knowing.

    Also, DMM's are very high-impedance, you can measure 'dangerous' voltages by just holding the leads in the air. Like any piece of lab gear, it's nice to know when you can believe it's output.

  • by Anonymous Coward on Wednesday February 07, 2007 @05:04PM (#17925740)

    I was sitting on the toilet with my Dell on my lap, taking a nice long poop, and I got shocked through my asshole!

  • by King_TJ (85913) on Wednesday February 07, 2007 @05:14PM (#17925858) Journal
    I'd like to submit Logitech to the list!

    I purchased one of their MX1000 laser mice when it was a brand new item, and while it was excellent - my 4 year old dropped it on the floor one too many times. The center rocker button surrounding the scroll wheel started sticking occasionally, causing things to scroll, out of control, in web browsers, MS Word, etc.

    Seeing it was under Logitech's warranty, I figured it couldn't hurt to give them a call - to see if they might be able to sell me a used/refurbished replacement mouse inexpensively or something, given the circumstances.

    Instead, the sales rep. looked up its serial number to confirm it was under warranty, and simply said "A brand new replacement is on its way." I asked if they needed the old mouse back, and I was told "No. You may as well keep it to have a spare charging base or something." Within a week, a new mouse was at my doorstep, in the retail packaging!
  • by Animats (122034) on Wednesday February 07, 2007 @06:00PM (#17926508) Homepage

    You're right; NEC article 406 says that the correct marking is "No Equipment Ground" in that situation.

  • I had this problem (Score:2, Informative)

    by Cunk (643486) on Wednesday February 07, 2007 @07:28PM (#17927812)
    I noticed this problem on my E1705 while I was in Israel recently. For days I experienced occasional stabs of pain in my left forearm whenever I had it pressed against the front of the laptop. I kept looking for something sharp or something that could have been grabbing the hairs on my arm but eventually I noticed a couple of tiny spots of bare metal on the housing where the paint had worn off. Immediately I suspected live voltage and sure enough when I put a voltmeter to it I could measure 30-40 VDC (never thought to measure AC) at the bare spot. And I noticed it would slowly charge up after a discharge.

    However, the problem went away once I came home to the U.S. and I assumed it was related to the 220V service in Israel. Although this doesn't make much sense since the DC power supply should be supplying the same voltage to the laptop in either case.
  • by Prune (557140) on Thursday February 08, 2007 @07:50AM (#17932588)
    WTF? As one comment already explained, the problem only occurs when ungrounded power adapters are used. Three-pronged plug grounded ones remove this problem. So clearly it's not the issue of the EMI filter you described. As another post explained, the issue is capacitive coupling between the primary and secondary windings in the switching transformer. I am sorry that your misinforming post got moderated highly.

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