Solved Preventing electrostatic damage to PC and Symptoms of ESD?

September 6, 2013 at 03:43:58
Specs: W7
I'll admit I never actually used an anti static wrist strap or anything like that before and it seems that things worked out fine. I just touched the metal of the case like some people say, but that is with the power cord totally unplugged.

But next time I do it I'll want to make sure I do it properly, and upon further reading it seems like there are too many conflicting reports. Some say the PSU has to be plugged in to be properly grounded, while others say to unplug. If it's unplugged, does touching the case metal discharge yourself, considering it's not in contact with the ground at all? How does that work?

Also, in the event that there is static damage to parts, since even voltages unnoticeable to humans can damage hardware with only minor symptoms, what sort of things would indicate that hardware has been damaged by ESD? i.e how would I know?

If I use a wrist strap and connect it to the case's metal, and nothing is plugged in, is that the correct way to do it?


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#1
September 6, 2013 at 03:58:25
If it's unplugged, does touching the case metal discharge yourself, considering it's not in contact with the ground at all? How does that work?

It doesn't. To discharge static there must be a path to earth. Without it there is nowhere for the static to go.

There is no definitive way you can tell if ESD has damaged something but you may suspect it when things stop working for no apparent reason.

Stuart


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#2
September 6, 2013 at 05:42:09
So it needs to be plugged in? But then how does it ground if the switch is off? Sorry I don't know much about electrical wiring

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#3
September 6, 2013 at 05:49:11
✔ Best Answer
Switches only interrupt the current carrying conductors. The ground conductor should always have continuity to earth. If you have an On/Off switch on the power supply, you can use that to interrupt the AC power while maintaining ground to earth.

All this assumes your AC wiring is newer 3 conductor and you are not using any adapters that circumvent the ground.

So, it is best to have the computer plugged in but the AC interrupted by the power supply switch or by some other device between the AC mains and the computer.


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Related Solutions

#4
September 6, 2013 at 06:12:07
Would that be effectively just having the third ground prong in the socket? (like if I were to break off the active and neutral prongs it would have the same effect?)

So is the general rule, plug in the PSU but make sure everything is completely off?


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#5
September 6, 2013 at 06:34:35
According to
It says "What is important in this whole process is not that the items being worked on are at absolute ground, but that they are at zero potential (voltage) in relation to each other... For field work, where this isn't available, unplug the computer, open the case and clip your antistatic wristband to the computer case so you're the same potential."

Does that mean if the PC is unplugged and your band is connected to the metal of the case, you will be at the same voltage as the case and so there will be no ESD?


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#6
September 6, 2013 at 07:34:25
That is correct, as long as there is no difference in potential between you and the computer you are safe. You could both be at a million volts but if you're both at the same potential, there will be no current flow thus no discharge.

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#7
September 6, 2013 at 07:56:33
Okay so then would it be true that the best way to go is to not have the PC plugged into anything at all, but have the wrist strap attached to the metal?

I'm not really a physicist so I do find it a bit confounding that this works


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#8
September 6, 2013 at 08:26:15
You could both be at a million volts but if you're both at the same potential, there will be no current flow thus no discharge.

You are right, there will be no discharge - until you touch a component on the motherboard that is isolated from the earth, or a new component that has never been anywhere near the computer then zap - its fried.

Stuart


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#9
September 6, 2013 at 10:10:23
Run with the last line of response #3, whether or not you are using a wrist band.

Always pop back and let us know the outcome - thanks


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#10
September 6, 2013 at 10:24:22
"You are right, there will be no discharge - until you touch a component on the motherboard that is isolated from the earth"

Then grounding the chassis wouldn't matter anyway if it was isolated since it wouldn't discharge.

And if you were grounded unless the new component was also grounded then chances are it has some potential from just being held or moving around and could theoretically be fried by grabbing it to whether you were grounded or not. Hopefully any component should still be in a static proof bag and the static will drain off when you touch the bag.

Bottom line, do what OtheHill suggested and Derek confirmed, plug the computer in so it is grounded. Touch the chassis so you are at the same potential and do not remove any components from the static bag until you are ready to use them. Touching the bag will put it at the same potential as well.

message edited by THX 1138


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#11
September 6, 2013 at 10:34:57
As often as not ESD comes about because "you" are charged (shoes on carpet - friction and so forth) with respect to ground. If the case is grounded then you will discharge safely. If the case is not grounded then the discharge will attempt to find its way to ground via your computer - the exact path is uncertain so it could zap something.

Always pop back and let us know the outcome - thanks


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#12
September 6, 2013 at 14:03:43
I agree that the best thing to do is make sure both you and the pc case are neutral but I think that what really matters is that there is no potential difference between you and the pc. By touching the case when you are about to start the work you put yourself and the case at the same charge. This is not a best practice rule though because if you rub your leg on the desk leg or shuffle your feet on the carpet as you are working you will create a difference in charge and can then damage components. In days gone by components were MUCH more sensitive do ESD but it is still a good idea to wear the wrist strap. I've been working on PC's for decades and never once wore a wrist strap and never had a problem but I work on a concrete floor and am very careful to touch the case before plugging or unplugging any chips or boards.

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#13
September 6, 2013 at 14:18:09
It might sound bonkers but I often take my shoes off when working on powered off computers. That way you keep yourself at earth potential - same potential as the case if you touch that when the ground is connected.

Always pop back and let us know the outcome - thanks

message edited by Derek


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#14
September 6, 2013 at 15:18:33
I live where the humidity for most of the year is around 10%. Static is a big problem especially in the winter (in the summer I have the swamp cooler going). It's become second nature for me to intentionally tap metal appliances--washer, dryer, stove, refrigerator--when I'm near them so I won't be startled by getting zapped when I'm not expecting it.

When I go to the computer I tap the metal brace beneath the table and usually the metal computer case. That's always been enough for this setup. The last computer I zapped was a commodore 64 so it's been awhile.

Take precautions but don't overthink it.


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#15
September 6, 2013 at 19:11:34
I remember working in a bank in the mid 1980s where we had some first generation teller terminals. Olivetti TC800. These were extremely sensitive to static and would shut down or freeze up if you touched the keyboard without grounding first on the metal trolley they were mounted to. They were robust enough though that performing a full shutdown and restart would bring them back online. We used to spray the carpets with anti-static mist in an effort to avoid the problem.
Since I started tinkering with the insides of computers in the late 90s I've never damaged one with static and adopted the practice of touching the case before any components.

Goin' Fishin' (Some day)


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#16
September 6, 2013 at 19:22:24
When people say to touch the case, is that with the plug in but switch off? Or totally unplugged and isolated?

Edit: Looks like I didn't read the link I provided fully. It also says "Touch the antistatic packaging of each component to bare metal on the case before opening to be sure they're the same potential. Theoretically you handling the bag should be sufficient, but this makes sure."
Does this mean I can isolate everything, as long as I touch the antistatic packaging to the case metal? SO CONFUSING :(

message edited by yogalD


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#17
September 6, 2013 at 22:38:13
Touching the anti-static packaging will do nothing for the component inside it. The packaging is designed to insulate the component from outside influences.

If you are at anything other than 0 potential relative to earth then you will zap the component when you remove it from the packaging.

YogaId. You are getting too much tied up with the getting you and the case at the same potential - it is irrelevant. It is the potential between you and Earth that matters, the case is just a route to earth via the earth conductor in the mains lead,

Stuart


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#18
September 6, 2013 at 23:15:03
But if I am grounded and the case is not, there is still a potential difference there and ESD risk right? Or not?
So the best way is: case plugged, switch off, wristband to case? What about if you plug the wrist band into the third (ground) hole in the socket?

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#19
September 6, 2013 at 23:21:35
I you want to equalize static potential between you and the metal case just touch it. Someone above gave excellent advice when he said ". . . don't overthink it." Oh, that was me.

message edited by DAVEINCAPS


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#20
September 6, 2013 at 23:34:39
Well that would be a lot easier if everyone could just agree on something
also I want to take zero risk next time after hearing that static damage could almost be unnoticeable and that most faulty hardware is actually a result of esd.

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#21
September 6, 2013 at 23:36:08
If you want to earth-ground everything then yeah, you can use the ground prong hole from a 3-prong wall socket. Or the screw that holds the plastic plate over the socket is usually screwed into the conduit which is grounded. Or you can clamp a wire to an outside water faucet, like we used to do with crystal radios, and run the wire inside and connect it to whatever needs grounded. (Outside faucets are preferred because most houses have at least some internal plastic water pipes.)

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#22
September 6, 2013 at 23:38:49
You could ground yourself by connecting your wrist band to a radiator for instance. But why bother with a radiator which may be on the other side of the room when you have a perfectly good ground source sitting on your desk.

Stuart


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#23
September 7, 2013 at 00:32:35
I think if I was as worried about it as you were I'd make one myself. I'd go to a hardware store and get a 3-prong plug and a few feet of about 16 gauge wire. I'd connect the wire to the grounding terminal on the plug. The other end of the wire I'd screw to a small metal strip and leave it on the computer table. Then with the plug in the wall socket all you'd need to do is touch the strip to ground yourself. Touch the strip to the computer case and it's grounded too. You don't need silly wrist straps. You're not generating static electricity just sitting in a chair.

Heck, someone's probably already invented that. Google around enough and you'll likely find a seller.

You don't need to worry about what's inside the case unless you open it up and poke around inside. And then the same precautions apply--just ground yourself on the strip and you're good to go. Well, ya know, unplug the power cord before digging around in there.


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#24
September 7, 2013 at 00:47:33
Ok. About the ground wire in the socket, is that one basically isolated from any sort of electricity and does the same thing whether or not the switch is on or not?
Like, if I were to stick metal into the ground wire if the switch is on, like a fool, nothign would happen?

message edited by yogalD


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#25
September 7, 2013 at 02:50:47
Assuming the socket is wired correctly there shouldn't be a problem. I wouldn't just stick a wire in it though. You should use a 3-prong plug with only the ground terminal connected. Don't mess with something lke that unless you're sure you know what you're doing. And like I said above, someone has probably already invented that--it seems like such an obvious device.

Don't be in a rush. Others may post in with better ideas tomorrow.


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#26
September 7, 2013 at 03:05:22
So even though the switch is off the ground wire still "works", is that correct?

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#27
September 7, 2013 at 03:42:56
Yeah, the ground connection in the wall socket isn't affected by the on/off switch of any electrical device that's plugged into it. It's always grounded. That's why I said you only need to connect the ground terminal in the home-made grounding device.

You're up kind of late to be in the US. If you're in another country the wiring in your wall socket may be completely different.


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#28
September 7, 2013 at 03:44:21
Yes. That's the whole principal of the thing. The power is off but there is still a path to ground. The ground wire is never switched, ever. It is a permanent connection while the computer is plugged into the mains.

Stuart


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#29
September 7, 2013 at 04:02:50
Actually I live in Australia and it's only 9PM (and we just had an election, heh). I recently heard that US sockets don't have switches; is this true? Because if it is so, then that is probably the source of most of the confusion right?

Anyway, so that's sorted. Plug in, power off, strap to case = ground.
Thanks guys.

message edited by yogalD


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#30
September 7, 2013 at 07:50:04
A switch or isolator never breaks the ground wire, whether it is on a wall socket or on a computer. I'm sure this applies to any part of the world which uses a ground connection. To break the ground wire could introduce a safety risk.

"easier if everyone could just agree on something"
That's because we are trying to tread the line between the perfect answer and practicalities - opinions then creep in.

Always pop back and let us know the outcome - thanks


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#31
September 7, 2013 at 08:30:35
The switch is either on the power supply itself or a power strip/surge protector. Either will do. Most power supplies I have seen have a switch on them.

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#32
September 7, 2013 at 09:31:38
Most power supplies I have seen have a switch on them

The latest PC's don't always have a switch on the back - including the HP that I'm using right now. It surprised me too.

Always pop back and let us know the outcome - thanks


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#33
September 7, 2013 at 21:24:41
Is it true that you don't have wall switches in the US?

Also just as an aside, let's imagine there was a power supply that only used a two prong plug (ie no ground... not sure if that even exists), would that mean that it wouldn't be safe to ground as there is none?


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#34
September 7, 2013 at 22:13:23
We have light switches for ceiling lights but generally homes here don't have wall sockets controlled by a switch. You plug something in and it's powered. The only exception is sometimes a wall socket will be wired to a wall switch--exactly like a light switch. Usually you plug a lamp into that wall socket. That way if you come home and it's dark you don't have to stumble around in the dark. You flip on the wall switch which enables the wall socket the lamp is plugged in to. If the switch on the lamp is already on then you have light!

Out in the garage we have the curcuit breaker box. Each curcuit breaker controls a few power outlets up to the breaker's rated amperage.

A lot of older homes only had the 2-prong sockets. If someone wanted to use an appliance with a 3-prong plug they had two options. One way was to use an adapter. Some of the adapters simply ignored the ground prong while some had a metal grounding terminal that matched up to the screw that held the wall socket face plate. So you could remove that screw, put it through the terminal and then screw it back together. The conduit system was grounded so that worked out OK.

The other way was to just cut off the appliance's ground prong so it'd fit in their socket.

I think building codes now require 3-prong grounding wall sockets.

message edited by DAVEINCAPS


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#35
September 7, 2013 at 23:14:36
I once had a long discussion about US electrics with another electrical engineer, who was a previous forum member. I came away most surprised how happy go lucky it all seemed to be compared to the UK - nearly fell of my seat. There seemed to be huge differences. One reason could be that in the UK (and Australia) we run at 230V so we have to be far more careful. The US run at about half that.

As regards adding ground wires, the cable thickness should be sufficient to carry the fault current without rupturing before the protective fuse or device. There is a safety margin of-course.

Be careful though because we are touching on questions of personal safety and you should always consult the regulations that apply in your own country. The voltage differences come into play too. It does seem as if the UK might be a closer comparison with Australia, 2 prong plugs went out about 60 years ago here. The only time they are used here now is for electric razor sockets but these are fitted with an isolation transformer, hence the dangers of electric shock are reduced. You cannot buy a wall socket in the UK that has no switch.

Always pop back and let us know the outcome - thanks

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#36
September 7, 2013 at 23:47:04
prong plugs went out about 60 years ago here

Even longer than that, When I was young plugs and sockets all had three pins, only the pins were round unlike the modern rectangular ones and were rated at 15 Amps. Even the smaller 10 Amps plugs were three pins.

I got my first electric shock when I was about five years old poking around inside a plug socket to see how it worked. The had no shutters on them like modern sockets do to prevent inquisitive kids from electrocuting themselves.

Stuart


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#37
September 8, 2013 at 01:20:29
It's probably been aboiut 60 years here too. The house I have now was built in 1980 and has all 3-prong sockets and GFCI protected sockets in the bathrooms. When I was a kid the house we lived in was probably built in the 1950's and only had 2-prong sockets.

I've noticed most new power tools now have just 2-prong plugs. They're always advertised as being 'double insulated', which I've figured out just means they're made out of plastic. There's no exposed metal, at least on the hand holds, to get shocked with. So I guess the insulated wires count as one layer and the plastic is the second layer of insulation.


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#38
September 8, 2013 at 01:50:22
This explains the different classes and double insulation.

http://en.wikipedia.org/wiki/Applia...

Incidentally the three pin round socket was introduced in the UK in 1934. When the UK became full members of the EU, the EU standardisation committee tried to get the UK to change their electrical safety system to a European standard. The UK quite rightly told the EU there was no chance as our system far exceeded any safety rules in place in the rest of Europe, most of which was still using reversible two pin plugs.

Stuart


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#39
September 8, 2013 at 04:43:45
Gonna wrap this up now, thanks guys.

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