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Noldor
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Static and motherboards

Thu Jun 08, 2017 3:03 am

Hi, I intend to add 4 GB to my HP G3 430 laptop (which currently has only 4 GB DDR4-2400). Question is: what measures should be taken to reduce the risk of static discharge? Previously, I've personally replaced parts only in desktops, so I wasn't really extra-cautious about it, because, generally, the chances of a static shock are small and, even if something happened to the (cheap) motherboards I was using, it wasn't the end of the world. But now since I want to do this to a laptop, I have to be more cautious than usual, because replacing a laptop's motherboard is a much bigger headache. Is touching a metal object sufficient to get rid of any static?
Second, can you cause a static discharge to go into the motherboard even if you don't touch it directly? (Sometimes, it is technically possible to insert a RAM module without actually touching the motherboard).
Thanks in advance.
 
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Re: Static and motherboards

Thu Jun 08, 2017 5:33 am

Just touching a metal object isn't enough, it needs to be a large (preferably grounded) metal object.

Obviously, the better way to do this is to use a proper (and properly grounded) ESD wrist strap. They're not expensive. Even better still would be the wrist strap + a grounded ESD mat (obviously more expensive than just the strap, but still not *that* expensive).

In the absence of an ESD wrist strap and/or mat, your best bet is probably to plug a USB cable into one of the laptop's USB ports, and touch the outer metal shell of the plug at the other end of the cable. This will ensure that you are at the same electrical potential as the motherboard's ground plane.

Also, beware the "cordless" ESD straps. These are snake oil, and do NOT provide meaningful ESD protection.
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Re: Static and motherboards

Thu Jun 08, 2017 6:30 am

just brew it! wrote:
Just touching a metal object isn't enough, it needs to be a large (preferably grounded) metal object.

Obviously, the better way to do this is to use a proper (and properly grounded) ESD wrist strap. They're not expensive. Even better still would be the wrist strap + a grounded ESD mat (obviously more expensive than just the strap, but still not *that* expensive).

In the absence of an ESD wrist strap and/or mat, your best bet is probably to plug a USB cable into one of the laptop's USB ports, and touch the outer metal shell of the plug at the other end of the cable. This will ensure that you are at the same electrical potential as the motherboard's ground plane.

Also, beware the "cordless" ESD straps. These are snake oil, and do NOT provide meaningful ESD protection.


Thanks. What about my second question?
 
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Re: Static and motherboards

Thu Jun 08, 2017 8:17 am

Yes, you can. How close you need to get depends on the magnitude of the static charge. But even with a small charge, as soon as you touch the DIMM to the socket, any residual charge on your body will flow into the motherboard through the DIMM (potentially damaging both).

In one extreme case, I damaged a keyboard and PC by taking off my coat (so I was really charged up), and immediately sitting down at my desk to log in (this was at work). As I was reaching for the keyboard, before I had even touched the keys, a spark jumped from one of my fingertips into the keyboard. The Shift keys on that keyboard didn't work after that, and it killed the USB port the keyboard was plugged into. And USB ports are even designed to take some abuse, with protective measures against ESD discharge.
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Re: Static and motherboards

Thu Jun 08, 2017 9:23 am

just brew it! wrote:
Yes, you can. How close you need to get depends on the magnitude of the static charge. But even with a small charge, as soon as you touch the DIMM to the socket, any residual charge on your body will flow into the motherboard through the DIMM (potentially damaging both).

In one extreme case, I damaged a keyboard and PC by taking off my coat (so I was really charged up), and immediately sitting down at my desk to log in (this was at work). As I was reaching for the keyboard, before I had even touched the keys, a spark jumped from one of my fingertips into the keyboard. The Shift keys on that keyboard didn't work after that, and it killed the USB port the keyboard was plugged into. And USB ports are even designed to take some abuse, with protective measures against ESD discharge.


In case of an ESD, does the damage always become apparent immediately, as it happened in the case described above, or after some period?
Or, more specifically, since ESD might be weak enough that you don't feel it, how do you tell for sure if everything went fine during the manipulation of the pc?
 
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Re: Static and motherboards

Thu Jun 08, 2017 9:32 am

Noldor wrote:
In case of an ESD, does the damage always become apparent immediately, as it happened in the case described above, or after some period?

It can go either way. It can cause immediate damage, or it can cause latent damage that worsens over time, or it can just make things less stable than they would've been otherwise.

Noldor wrote:
Or, more specifically, since ESD might be weak enough that you don't feel it, how do you tell for sure if everything went fine during the manipulation of the pc?

You don't. The best you can do is minimize the chances of it happening.
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Re: Static and motherboards

Thu Jun 08, 2017 9:47 am

just brew it! wrote:
Just touching a metal object isn't enough, it needs to be a large (preferably grounded) metal object.



Speaking of which, I assume touching something like a metal sink, water pipe or the external metal casing of some device (for instance, a toaster) connected to a grounded power outlet would do, right?
Is that better than your second recommendation (the one about touching the USB metallic part)?

Edited: Just dawned on me, but if the body of the laptop is mostly metallic, and placed in turn on a metallic cooling pad, do I even need to bother with an USB?
And, btw, what exactly do you mean by "large"? Obviously, that means larger than a pin, but do you have in mind "router-sized" large, desktop-sized large or car-sized large? (ok, maybe the last was an exaggeration :P ). How large should the metallic object be? I keep my laptop, as I mentioned, on a metallic 15,6 cooling pad, so would that qualify?
 
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Re: Static and motherboards

Thu Jun 08, 2017 10:16 am

Noldor wrote:
just brew it! wrote:
Just touching a metal object isn't enough, it needs to be a large (preferably grounded) metal object.

Speaking of which, I assume touching something like a metal sink, water pipe or the external metal casing of some device (for instance, a toaster) connected to a grounded power outlet would do, right?

Yes, provided the metal casing of the appliance is in fact grounded. AFAIK most toasters are not (and our toaster in fact has a 2-wire cord, so the outer casing definitely isn't grounded).

Noldor wrote:
Is that better than your second recommendation (the one about touching the USB metallic part)?

Maybe?

The goal is to make sure that everything (laptop, you, and the DIMM) are at the same electrical potential. If the laptop has been sitting a while (e.g. wasn't just pulled out of a backpack or something), excess charge should've bled off, putting it close to ground potential. If I was being extra-paranoid I'd touch the grounded object and the USB connector at the same time, to ensure that everything is at ground potential. (I'm not normally that paranoid about ESD unless I'm dealing with something really expensive, or if the relative humidity is very low.)
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Re: Static and motherboards

Thu Jun 08, 2017 10:28 am

I've partially disassembled and cleaned or upgraded multiple laptops with only a few precautions. There's always a risk of ESD damage unless you're wearing the grounded wrist strap and standing on a rated mat, but most problems can be eliminated by wearing all-cotton clothing (definitely avoid acrylic, wool, and polyester...synthetic "track suits" and stretchy athletic clothes are no good) and working in an area that's not excessively dry. If it's one of those days where your finger gets popped on every doorknob, your laptop will have a bad time unless you can raise the ambient humidity somehow.

An ideal place to work, if you have one, is in an unfinished space with a bare concrete floor. Reinforced concrete is actually a very good conductor and it doesn't generate charge when you scuff your shoes.
Last edited by ludi on Thu Jun 08, 2017 10:32 am, edited 1 time in total.
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Noldor
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Re: Static and motherboards

Thu Jun 08, 2017 10:31 am

just brew it! wrote:
Noldor wrote:
just brew it! wrote:
Just touching a metal object isn't enough, it needs to be a large (preferably grounded) metal object.

Speaking of which, I assume touching something like a metal sink, water pipe or the external metal casing of some device (for instance, a toaster) connected to a grounded power outlet would do, right?

Yes, provided the metal casing of the appliance is in fact grounded. AFAIK most toasters are not (and our toaster in fact has a 2-wire cord, so the outer casing definitely isn't grounded).



Could you elaborate?

If the laptop has been sitting a while (e.g. wasn't just pulled out of a backpack or something), excess charge should've bled off, putting it close to ground potential


Is that a good or bad thing?

If I was being extra-paranoid I'd touch the grounded object and the USB connector at the same time, to ensure that everything is at ground potential. (I'm not normally that paranoid about ESD unless I'm dealing with something really expensive, or if the relative humidity is very low.)


With desktops, neither am I, as I never bothered too much with this whenever I had to rummage through one and nothing ever happened (granted, usually their cases had metal part which I had to touch in order to take them apart, before I could reach the motherboard - and that sufficed, as far as I was concerned). With a laptop, though, I am more wary, because it's a pain in the ass to replace some parts (other than drive and RAM) if something goes wrong.
 
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Re: Static and motherboards

Thu Jun 08, 2017 4:14 pm

Noldor wrote:
just brew it! wrote:
Noldor wrote:
Speaking of which, I assume touching something like a metal sink, water pipe or the external metal casing of some device (for instance, a toaster) connected to a grounded power outlet would do, right?

Yes, provided the metal casing of the appliance is in fact grounded. AFAIK most toasters are not (and our toaster in fact has a 2-wire cord, so the outer casing definitely isn't grounded).

Could you elaborate?

In the US, power plugs on small appliances can have either a 2-prong plug or a 3-prong plug. If the 3rd prong is present, it is a protective ground, which is typically connected to the metal chassis (if the appliance has one). If there isn't a 3rd prong, then the chassis is not grounded by definition, since there's no path to ground available.

Noldor wrote:
just brew it! wrote:
If the laptop has been sitting a while (e.g. wasn't just pulled out of a backpack or something), excess charge should've bled off, putting it close to ground potential

Is that a good or bad thing?

Good thing. You don't want any residual charge on anything.

Noldor wrote:
just brew it! wrote:
If I was being extra-paranoid I'd touch the grounded object and the USB connector at the same time, to ensure that everything is at ground potential. (I'm not normally that paranoid about ESD unless I'm dealing with something really expensive, or if the relative humidity is very low.)

With desktops, neither am I, as I never bothered too much with this whenever I had to rummage through one and nothing ever happened (granted, usually their cases had metal part which I had to touch in order to take them apart, before I could reach the motherboard - and that sufficed, as far as I was concerned). With a laptop, though, I am more wary, because it's a pain in the ass to replace some parts (other than drive and RAM) if something goes wrong.

Yup. Generally desktops are less risky, since the metal chassis provides an easy way to discharge any ESD on your body.
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