Static Prevention

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FRAGaLOT

The only reason to unplug the PSU from the wall outlet is to avoid shock from the outlet. Most PSUs have a master power switch on them you can turn off to avoid that. You'll still be connected to ground with the switch off, assuming your outlets are grounded; just because it has 3 prong socket dosen't mean it's acctually grounded.  So as you touch the chassis as you're working on it, you'll ground your self often enough to never really build up a static charge to cause any damage.

Also, Dexter243, please PLEASE use spell check when you post next time.  My brain hurts trying to read typoed posts. No one can take you seriously if you keep writing posts like that; espeically when you're calling people FOOLS at the same time. And why do you start nearly every post with "Nutcracklng snack?" Are you mental?

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Dexter243

Nutcracklng snack

ok folks a bit of info 

you know thay funny looking plug in your bathroom with the red button on it 

that is a gfci plug and that is ther to kick off if ther is any kind of short and if you look clos 

ther all any place that is clos to water becous water maks it very easy for you to get a shock 

and the joker that sed 110 wont kill well tell that to the many people that are dead from a small shok 

it only tals 7mil volts to stop the hart and then you die and all you have to do if have a shock travl

threw your body in the right path and it can kill you

be safe not stuped unplug system 

and tuch the case often to prevent a charg build up ,.

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Tekzel

You might want to verify your information before you post.  7 milli-volts would be entirely harmless.  7 milli-AMPs would be dangerous. Idiot.

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Ntldr

I don't know if you can't spell or if you are just being retarded but how about we fix your post so it makes a bit more sense to someone that reads it. 

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LARRYROD77

you know what i just read all these comments and my god the ground is basically the leg of the table?! are you serious?! dc voltage can kill too!  remember that! im just tryin to help here. imay be a newbie here and im not tryin to piss anyone off but jeez people! we are talking about electricity here. bottom line be careful! thats all I'm tryin to say.

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Tekzel

Denied, DC voltage can not kill you.  It is CURRENT (as measured by amperage) that kills, not Voltage.  Voltage is only an expression of the differential between two points. (Actually I think its across a plane or something, but thats a long time ago, two points will work). A static discharge can measure 10kv to 20kv, but it is harmless.  Because it is extremely low amperage.

I know this is quibbling, but it is important to know that the voltage reading only signifies how much current a circuit CAN carry, not how much it IS carrying, and the IS is the most important thing to know. Think of voltage as the diameter of a pipe, which partially defines how much water flow it can carry. The other part is the water pressure, which would be the current. You could have a very small trickle going through a 12in diameter pipe. Or you could have a 200psi stream shooting out the other end.

Regarding DC vs AC, absolutely, DC can kill.  Just not AS readily as AC.  The thing that makes AC so dangerous isn't that it alternates, but the frequency of the swing. Household current here in the US is 60hz, thats 60 alternations per second which is dangerously close to the number of resting heartbeats per minute we have. This can cause fibrillation in our heart and cause it to lose sync. Which I am sure everyone knows is baaaad mojo.

Edit: I came back a little while later and read through my post again, and realized I said "dangerously close to the number of heartbeats per SECOND we have".  Oops, I meant per minute.

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LARRYROD77

as someone who deals with electricity every day i can tell all of you that no matter what the voltage is it probably wont kill you. its the amperage! most capacitors on a mobo wont kill you but they will give you a nasty shock. ground yourself no matter what. wrist strap. when your working on a mobo is not you that you worried about is it?! its the mobo! your trying to eliminate the leftover charge thats on you. thats all! electricty kills no matter what voltage. always remember that.

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Edahsetin

Usually I leave a computer connected to a power bar thats shut off.  No power is going through it, but it should still be grounded, which is always a good thing.

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COMMANDER_COOK

I leave computers plugged in unless I'm using a screwdriver.

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Dexter243

Nutcracklng snack

you are a fool if you leave the system pluged in wile you are working on it all it taks is a short in the psu and you have 110v aplyed to that case 

i am not joking or trying to make any one look bad 

DO NOT KEEP SYSTEM PLUGED IN WHEN WORKING ON IT 

as for the static charg just tuching the case side befor you reach in side will equle out the 

+ and the - electrons between you and the system and buy the way ther GROUND in the system pluged to the wall is for that very thing to alow AC volt's a much easer path to take back to the ac transformer just in case ther is a short to frame becouse the body is a very bad conducter the power will take the path of least resistence it is not there to de static the system 

and it will not destatic the system 

just my 2cents

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Tekzel

Wow, that was painful to read.  I sincerely hope that English is a second, or distant third, language for you.

Regardless, your "youa are a fool" is ridiculous.  As I stated, if there is a short causing the chassis to get household current you would know it generally when you bend down to unplug the thing.  Anyone here carefully reach around, avoiding the metal of the case, and pull out the plug before they move it?  I didn't think so.  You should think before you post.

And on that note, while it is never a good idea to intentionally grab a fork and jam it in an outlet, household current isn't AS bad as all that.  As long as the path the ground doesn't go right through your heart, and you are able to let go (something I have NEVER had a problem doing when I get a fistfull of household current) quickly, 110v won't kill a healthy adult. Again, I should reiterate: I am not saying its isnt a good idea to avoid it whenever possible. What I am saying, there is no need to go beyond reasonable precautions when dealing with it.

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quickone

 Agreed, static discharge happens because of the DIFFERENCE between charges, without difference there is no flow and therefore no worries. Touch the case and you'll equalize, but do it often, as change occures as soon as you let go, don't want it to get to big.  

 

As for making sure it is unpluged, that 3rd prong is there to protect the system/not start a fire, it won't help you much if there is a short.  That being said 110 won't kill you, it will scare the hell out of you and make your arm numb for a while but you won't die, after you know what you're doing we usually don't even wear gloves while working with live 110.  220 on the otherhand, like for a dryer, that'll make for a bad day/week/month.  Maybe a computer used for Folding could use 220, oh the system you could build...  

 

 

~~The difference between insanity and genius is merely succes~~

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bloodgain

I would just like to point out that 110V very much can kill you -- it's just unlikely to happen.  Anything under about 1000V will cause your muscles to contract, which is why it feels like getting punched in the chest (or hit by a baseball bat if it's 220V or more).  1000V+ causes the opposite reaction, which is why you get "knocked away".

It's this muscle contraction that can result in your death.  If you grabbed a live wire/rail/etc at 110V, your hand would clamp down, and you could quickly top out a 15-20A breaker.  The breaker *should* trip before you would even be rendered unconscious, but is not designed specifically to trip due to electrocution (GFCI is more reliable for that, but still not fool-proof).  According to US Consumer Product Safety and the National Institute for Occupational Safety and Health, about 411 people died from electrocution in 2001.  19% of those were due to large appliances and 11% were due to "installed household wiring", so we can estimate that about 100 people were killed by 110V current (if we assume some of those were 220V appliances).  That's still less than 1 in a million per year, but it does happen.

However, since we tend to touch things with the tips of our fingers (especially if you know what you're doing), usually you just get a good half-second jolt, cuss a bit, and move on.  Skilled electricians know and inherently trust simple facts like if you create a closed circuit, you can twist the hot wires together safely by hand.  However, since most people are *not* skilled electricians, they should *not* throw caution to the wind -- never work with hot (electrified) wires unless you know exactly what you're doing.  Even skilled electricians are supposed to "unground" or insulate themselves when working hot according to OSHA guidelines.

I don't mean to argue or be a stick in the mud.  I just don't want people to get the idea that 110V is safe and that they don't have to take precautions.  Always practice electrical safety, folks! Plus, getting popped still hurts like a SOB even if it doesn't injure you.

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COMMANDER_COOK

I learned with a camera. Those capacitors can shock you. They left two burnt places on my hand where I touched the terminals.

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jrocknyc

as long as you wear socks and rub your feet on the rug, then rub & stick some balloons onto your shirt, you'll be fine.

 

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WFUJay

I've personally built about 40-50 computers in my lifetime, either for myself, clients, family, or friends and never once have I used a grounding strap.  I just make sure to touch a doorknob before I start working and touch the computer case every so often while working.  Never once has static electricity from my body caused a piece of hardware to malfunction.  I think it's more of an urban legend than anything.

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lien_meat

I've built and worked on a pretty large number of computers in my day, and I haven't ever bothered with a grounding strap either.  I've never once had a computer fail because of it.  On my own computers, I've rebuilt them or added components many many times, and the only time I have ever had a computer fry is when it was running idle with a PSU problem or MB problem, usually due to really old age, but never because of my working on it without a grounding strap.  I know it's better to be grounded (in principle), but I honestly don't think the current you would put out from static buildup on your body is enough to fry most circuts, and I've actually never seen proof otherwise...
### I'm an idiot, and I approve this message ###

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RyanF

Almost every post here(and the response) has said that you should be grounding yourself to the case. This is a HUGE misconception. That silly little wrist strap you wear is actually a really big(3-5MOhm) resistor. If you were to simply ground yourself to the case, then you would be conducive to current flow, which is a bad thing. By wearing a big resistor, you limit the amount of current that can flow to/from you,and you've equalized your potential.

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Tekzel

Maybe I misunderstood what you are saying. It SOUNDS like you are saying the strap is to work as an insulator? If you are using a strap with a HUGE resistor, and then also touching the chassis, you aren't limiting anything.  The current would just avoid the path through the strap and using the path that includes your hand on the chassis.  Current takes the path of least resistance, which would be your arm and hand vs the strap with a big resistor. The strap isn't there to protect YOU, its there to provide a path to ground for any static buildup on your skin. Thats why it has a little alligator clip that you connect to a ground.  Which, ironically, I have seen many techs connect to to the chassis of the pc they are working on. Whats the point, you are going to be touching that anyway most of the time.

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K0BALT

I heard you're supposed to leave the PC plugged in, so it stays grounded through the outlet. I may be wrong though...

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Zombie30000

I work in a lab where  we use latex gloves all the time and I know they can build up a static charge.  We weigh out powders and the materials can fly off the balance and stick to your gloves if you don't keep up with the staticide.

We also test conductivity of gloves and most do not conduct well, therefore they can build up a charge easily even when you are grounded with a wrist strap.

 On the computer side I don't wear a strap eaither.  I just make sure to rest my elbows on the case whenever I reach inside. Insuring that the case and me are at the same voltage I never get a spark when components come together.  Again, that's just me, coincidence does not equal causation.

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Tekzel

I know it goes counter to accepted PC troubleshooting methodology, but having worked in PC repair shops for about 10 of the last 15 years, I have never once put on one of those goofy little wrist straps and have never zapped an electrical component with a static charge.

I work on them plugged in and make sure to touch the chassis to discharge any built up static. I should probably mention that I have also never killed myself by working on them plugged in, either. Frankly, I am pretty sure the DC output of even the 12v rail in a PC can't hurt you. AC is far more dangerous than DC. If there were a short that allowed the AC to pass into the PC anywhere outside the power supply, it would likely be to ground and since the chassis is grounded you would shock yourself just by putting a screwdriver to the screws and would know it already.

Of course, this isn't advice.  It is an alternate viewpoint.  

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gordonb

Then you have either been lucky or you have caused damage and didn't know it. Unlike in the movies, you don't have see and feel a giant spark and have the component smoking for there to be damage to electrical components.  As chips get smaller and smaller, and pack on more and more components, they are a lot more sensitive to ESD events.  Damage causing discharges can happen even if you don't see or feel anything. Also, ESD can cause something called latent damage, where a part is wekened but still works, only to fail at a later time.  

Yes, its good to ground youeself in the chassis, but charge can still build up on your body as you work.  If you touch the chassis often, you will probably be OK, but you are still taking a chance.

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Tekzel

Most of the time, you can feel the tingle of a static discharge. And as
I said, I keep it plugged in and am regularly in contact with the
grounded case.  While of course it is possible, I highly doubt I have
ever had a static discharge, small enough for me not to feel, in just
the right place to damage a component. Hell, thats probably on par with
winning a lottery.

So I disagree with your original point.  I deny that I have been especially lucky. Not that I believe in the concept of "luck" anyway.

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dread_ire

When I did repairs for Toshiba part of the training we had to go throgh for our certification was a lesson on ESD.  We were required to wear wrist straps when doing repairs on their notebooks because even a small ESD event could damage an IC, but not cause it to break.  However the system would start doing wonky things because an IC was only just slightly damaged but not totally broken.  My instructor said that they had xray'd parts in their labs and seen damage from ESD.  Keep in mind laptops are special beasts too.  Lots of plastic and not a lot of places to ground yourself out.

That said my instructor in college for my Technician certification always insisted that grounding yourself on the case frequently is just as good as a wrist strap and not nearly as annoying.   For my own desktops I ground myself out on the chassis during construction and I have never had an ESD related failure, knock wood.

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COMMANDER_COOK

The chassis, as you know, connects to the ground wire of your house's electrical system. So leaving it plugged in and frequently touching the case would be better on desktops in my opinion. Think about it. That ground wire goes outside and connects to a metal rod that goes some 7 feet into the ground vs. that wrist strap that goes to the leg of a table.

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