Teen electrocuted while salvaging parts from a computer

User Comments: 91

1. October 12, 2012 12:09 PM
   Guest said:

   Shocking...

   Reply
2. October 12, 2012 1:02 PM
   Guest said:

   Boys and girls, is this really can happen? I mean zapped from capacitor could lead to death? from my experience I once accidentally bumped with the capacitor with the size of a gluestick (but shorter in height) when checking/stripping one of my lab device (of course it's unplugged), I bumped it when I want to reach the cover, then what I got is a small electrical burn on left side of my boobs

   Reply
3. October 12, 2012 1:23 PM
   

   treetops said:

   Lol its not bad luck the kid was messing around in a power supply unit, which clearly warns people do not f with it, all over it. They really just needs one big sticker saying EVEN WITH POWER CORD UNPLUGGED FATAL CHARGES REMAIN. I wonder if he knew the risk.

   My first computer repair college related class in chapter one was like do not ever take apart a psu or monitor unless your a trained professional, your risking deathly electrocution.

   Reply
4. October 12, 2012 1:50 PM
   

   spydercanopus said:

   Probably a high-powered VIDEA GAME chip. Yall happy now?! Gamin' KILLS!

   Reply
5. October 12, 2012 2:35 PM
   

   Benny26, TechSpot Paladin, said:

   This is going to put the creeps into the next time I open up my PSU for cleaning. Even though I've done it probably more than a 100 times without a single shock I'll still have this on my mind for next time.

   There was more to this story I feel.

   Reply
6. October 12, 2012 2:45 PM
   wiyosaya said:

   First of all the primary capacitor or capacitors in a computer's switch mode powersupply (PSU) sit after the input rectifier, which converts the incoming AC voltage to DC voltage. In the case of 120VAC input power there is also a voltage doubler stage active which does what the name implies.

   Secondly if the PSU is a modern design it will instead have a APFC stage (Active Power Factor Correction) which sets the voltage at the primary capacitors to ca 400v

   Have you actually ever opened a cheap Chinese built PSU? (A $20 PSU as the linked news movie talks about)

   Most ones lack any and all input filtering, there are no X or Y capacitors, no MOV's and no coils to be seen, just jumper wires on the PCB where the missing components should be.

   What makes you think they would hesitate to not install the primaries bleeder resistor?

   I have a charger for a camera right here lacking exactly that, made in China of course.

   Actually the majority of PSU's power switches do not switch of both Line & Neutral, which is required by law in Europe.

   Because many European countries use the Schuko plug which is not polarized, meaning it can be inserted either way (AC power does not care, so we can flip the live and neutral in any equipment).

   This has the interesting side effect that when the PSU switch is off there might actually be power present through the entire PSU all the way back to the switch!

   All you have to do is provide a path for the Neutral and there will be a circuit formed.

   Like if you hold the PSU's chassis while touching the primary sides heatsinks!

   Doublers have not been needed on well-designed, modern power supplies for years. I'm sure you can check this out by reading the specs on any well-designed modern supply - which will not have an input voltage selection switch. Many modern switchers have an input voltage range of 100V-240V, and you don't need to select the input voltage with a switch. Just get the right line cord and plug it in to the local outlet. For example - [link] For a buck converter, it really does not matter what the input voltage is as long as it is sufficiently high enough over the output voltage to overcome conversion inefficiencies.

   So, what you are saying is that the kid had not unplugged the supply?

   Reply
7. October 12, 2012 2:50 PM
   Guest said:

   This is rather scary.

   I open my PSU every now and then to clean or to maintain it's fan.

   Best thing to do is to turn off power and leave the PSU unplugged for 24 hours before maintenance, especially anything with big capacitors.

   Reply
8. October 12, 2012 2:50 PM
   Staff
   

   Per Hansson, TS Server Guru, said:

   Wiyosaya: Uh yea if you had continued to read my post you might have come to the part where I talk about APFC

   I guess I could have made it clearer but with APFC there is no voltage doubler stage, only the APFC stage.

   But as for the charge in the capacitor this is actually even worse because it is an even higher voltage, which was my whole point to begin with

   Reply
9. October 12, 2012 3:31 PM
   

   cliffordcooley, TechSpot Paladin, said:

   Remember the 35mm camera's with flash? Them little bad boys put out a jolt as well.

   It never occurred to me how much voltage was needed to operate a camera flash, until I discharged the capacitors in one with my fingers. Talk about a wake up call, that was worse than being shocked by a wall outlet. I instantly formed a question of how a 3V DC device could shock worse than 120V AC wall outlet.

   How Camera Flashes Work

   The flash trigger is wired to the shutter mechanism. When you take a picture, the trigger closes briefly, connecting the capacitor to a second transformer. This transformer boosts the 200-volt current from the capacitor up to between 1,000 and 4,000 volts, and passes the high-voltage current onto the metal plate next to the flash tube. The momentary high voltage on the metal plate provides the necessary energy to ionize the xenon gas, making the gas conductive. The flash lights up in synch with the shutter opening.

   200V :eek: 1000 - 4000 :eek::eek::eek:

   From a 3V camera??? WOW

   Reply
10. October 12, 2012 3:52 PM
    2 people like this |
    Guest said:

    This REEKS of Urban Myth to me.

    Reply
11. October 12, 2012 4:11 PM
    Guest said:

    PSUs should be replaced not repaired. They are so cheap these days, even excellent quality high wattage units are reasonably priced for the job they do. The closest I ever get to the inside of a PSU is with compressed air to blow dust particles out.

    Over recent years of fixing computers I have also had instances of a computer running normally at a client's house only to have the PSU "blow" back at the workshop due to excess dust arcing and blowing the PSU as soon as the power cord was attached. Since then I have dusted PSUs out with compressed air before attaching a power cord. Respect electricity.

    Reply
12. October 12, 2012 4:13 PM
    Guest said:

    Well, maybe it is just sensationalism or maybe just bad luck?, I work as IT fixing computers and printers and in my 7+ years in the business I've been shocked by flybacks (CRT Monitors), I have shortcircuited capacitors of around 200V (the big ones), and maybe the worst was the flyback, it left me with headaches for 3 days, but didn't kill me, if this is true, the guy was either bare feet and/or wet and/or suffered of heart affections, only accurate info would tell us.

    Reply
13. October 12, 2012 5:01 PM
    andymac26 said:

    Or just short the cap out with an insulated screwdriver, been doing it for years in my industry. never damages anything.

    Yeah, read numbers on those big one, they can store pretty punch. Its a good idea to push a power button on an unplugged PC and leave it overnight for those charges to dissipate, before raplacing fan or capacitor.

    Reply
14. October 12, 2012 5:36 PM
    9Nails, TechSpot Paladin, said:

    My heart goes out to the father. I couldn't imagine the pain and loss of a child. The young man who lost his life working on a hobby that I've done thousands of times myself for business and personal use and never considered to be this dangerous. I hope that this is one of those very unusual set of circumstances and peculiar accidents which aren't common. But to lose a son, a young man starting his life, it is such a heart breaker.

    Reply
15. October 12, 2012 5:38 PM
    Guest said:

    IT always makes me wonder of how ignorant people are! Most users comment that they press the power after having disconnected the power cord. So let me guess you think the capacitor just going to discharge? Let me see. A computer using maybe 5 volts and is run by a 120 volt power source. So you think that small electronics going to just discharge it real quick. A laptop runs 3 to 8 hours on battery. So your system being a little bigger like lets say a desk top computer uses much more power then that. Think again. Even if you press that button for 3 hours there is still a chance that you will have a kick in there. Your best bet is to use gloves. Also when working on power supplies don't ground yourself for that is a deadly mistake. Also think of this a capacitor is an independent circuit. It stores over flow not usage. If there is a circuit it steps down the current by taking the access off. So how do you think you going to discharge it by simply pressing the power button while it is not plug in genius.

    Reply
16. October 12, 2012 6:02 PM
    1 person liked this |
    

    cliffordcooley, TechSpot Paladin, said:

    A computer using maybe 5 volts and is run by a 120 volt power source. So you think that small electronics going to just discharge it real quick. A laptop runs 3 to 8 hours on battery. So your system being a little bigger like lets say a desk top computer uses much more power then that. Think again. Even if you press that button for 3 hours there is still a chance that you will have a kick in there.

    Firstly - A normal desktop does not have a battery to keep it running for hours (thats what a power cord is for).

    Secondly - They were referring to pressing the Power Button and the motherboard sending a power good signal to the PSU, therefore switching the power rails on and quickly discharging any stored power inside the PSU.

    Also think of this a capacitor is an independent circuit. It stores over flow not usage. If there is a circuit it steps down the current by taking the access off.

    What???

    In short, capacitors are used to level off peak AC voltages to regulate a flat DC output for usage. These capacitors are not a sideline component, they just as important as any other component in the system. One faulty power capacitor and you could have massive amounts of voltage ripple through out the entire electronic system. Notice I said power capacitors because capacitors do have other functions of filtering frequencies.

    Your comment disgust me after reading your first sentence. You should never speak of others ignorance, unless you know exactly what you are saying.

    Reply
17. October 12, 2012 6:03 PM
    Prosercunus said:

    I wondering what he was doing. You never try to save or take parts from a PSU. Don't even open them.

    Properly dispose of them when they go bad.

    Reply
18. October 12, 2012 7:09 PM
    Guest said:

    A computer using maybe 5 volts and is run by a 120 volt power source. So you think that small electronics going to just discharge it real quick. A laptop runs 3 to 8 hours on battery. So your system being a little bigger like lets say a desk top computer uses much more power then that. Think again. Even if you press that button for 3 hours there is still a chance that you will have a kick in there.

    Firstly - A normal desktop does not have a battery to keep it running for hours (thats what a power cord is for).

    Secondly - They were referring to pressing the Power Button and the motherboard sending a power good signal to the PSU, therefore switching the power rails on and quickly discharging any stored power inside the PSU.

    Also think of this a capacitor is an independent circuit. It stores over flow not usage. If there is a circuit it steps down the current by taking the access off.

    What???

    In short, capacitors are used to level off peak AC voltages to regulate a flat DC output for usage. These capacitors are not a sideline component, they just as important as any other component in the system. One faulty power capacitor and you could have massive amounts of voltage ripple through out the entire electronic system. Notice I said power capacitors because capacitors do have other functions of filtering frequencies.

    Your comment disgust me after reading your first sentence. You should never speak of others ignorance, unless you know exactly what you are saying.

    I sugest that you don't comment if you have no clue of what you are talking about. Here is a quote for you.

    Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass, in filter networks, for smoothing the output of power supplies, in the resonant circuitsthat tune radios to particular frequencies, in electric power transmission systems for stabilizing voltage and power flow, and for many other purposes.[

    So as you see it is exactly as I commented. You can see a capacitor as an independent of AC or alternating current. It stores direct current while letting AC pass through. So if there is no ac to pass through do you think a stupid thing like a capacitor going to grow brains and convert dc to ac just so in can discharge for you genius.

    Reply
19. October 12, 2012 8:55 PM
    

    cliffordcooley, TechSpot Paladin, said:

    It stores direct current while letting AC pass through.

    Wrong, the capacitor charges creating a DC voltage which kills AC voltage. There is no pass through AC voltage. The property of having a DC PSU is to convert AC to DC. If you have an AC signal on the output of a DC power supply something is wrong. You should stop now before you embarrass yourself further. Ohhh, thats right you are hiding behind a guest account, no wonder you are saying things that don't make sense.

    Just to let you know you are implementing the definition of a filter capacitor as a power capacitor. The difference is one is in series with the circuit while the other is in parallel with the circuit. A power capacitor is placed in parallel with the circuit. A capacitor used as a filter placed in series with the circuit will allow AC frequencies to pass and effectively blocking DC voltages. DO NOT GET THE TWO MIXED UP!!!

    So if there is no ac to pass through do you think a stupid thing like a capacitor going to grow brains and convert dc to ac just so in can discharge for you genius.

    Lets get one thing straight, by that statement you seem to think that AC is a requirement for discharge. AC voltage can never be stored, therefor never discharged. A discharge will always be the release of a stored DC voltage. AC voltage can jump but that is not the same as discharging.

    Do us all a favor and be quiet so we can get back on topic. Paying our respects to the teen that died from a discharge that you obviously don't understand.

    Ohh and thanks for the links but I don't need a refresher course in basic electronics.

    Reply
20. October 13, 2012 1:04 AM
    

    cliffordcooley, TechSpot Paladin, said:

    So what do you think happens to the rest of voltage or energy when it gets steeped down.

    The voltages don't get stepped down, they are switched off, disconnected from the motherboard. Step-down is a term used when voltage goes through a step-down transformer. You can't even get the most basic terminology correct, so why would I listen to you about electronics. Stop talking shit and confusing people. If you didn't spread trash I wouldn't have anything to try and correct. And OMG for the first time in my 40 years of life someone is calling me a bully.

    I've derailed this thread long enough, good luck spreading your misconceptions and misguided truths around the Internet. I have had my fill of this conversation and have nothing further to say to you. Its sad really that you would pick this thread of all threads to play your games in.

    Reply
21. October 13, 2012 1:05 AM
    

    wartech0 said:

    I'm not a PS guru, so had no clue you could even get shocked, much less die from one.

    Not that I'd ever tear one apart, I'd have no reason to. But good thing to know and sorry to hear about the kid.

    PSU are nothing to mess with. The capacitors do carry enough current to kill if you grab a live terminal and ground with both hands. I have had a cap shock me out of a disposable camera before, it hurt pretty bad and luckily I was holding it in one hand. 60mA is enough to kill that isn't really a whole lot either.

    Reply
22. October 13, 2012 1:33 AM
    Guest said:

    http://hypertextbook.com/facts/2000/JackHsu.shtml

    it doesn't take much current to kill you

    Reply
23. October 13, 2012 2:16 AM
    Guest said:

    That doesn't work. Where does the electricity go if it's not connected to a ground? It stays inside the power supply.

    Pressing the power button after it's turned off would only drain any electricity in the motherboard or peripherals back into the PSU. Which is good, unless you plan on opening it...

    Reply
24. October 13, 2012 4:48 AM
    1 person liked this |
    veLa said:

    It's very simple. Never open a power supply.

    Reply
25. October 13, 2012 5:42 AM
    Staff
    

    Per Hansson, TS Server Guru, said:

    That doesn't work. Where does the electricity go if it's not connected to a ground? It stays inside the power supply.

    Pressing the power button after it's turned off would only drain any electricity in the motherboard or peripherals back into the PSU. Which is good, unless you plan on opening it...

    No it does not work like that.

    When you press the power button on a PSU not connected with a power cord the power stored in the capacitors is discharged and put to use, for example spinning the fans which you can see if you discharge a PSU this way.

    However I must stress that this is not a safe way to discharge a PSU, because it assumes the PSU is working properly, which as I said before it most likely is not if you feel the need to open it up and fix it!

    Reply

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