ESD questions, newbie introduction, PC cleaning warning

[guyaros]

Hello

My name is Guy, I am a student for Mechanical engineering so I am familiar only with the basics of electronics, plus I am a total newbie in this forums (1st post)  .

English is not my first language so please forgive me if I have grammar issues.

I have some questions regarding ESD and computers (PC).

At first Ill begin with a story that occur to me not too long ago:
My PC was in fully working order, totally fine, and my only intention was to clean the PC from dust (something I do from time to time).
I turned off my pc, disconnected all the wires, opened the door case
And then I made the first major mistake - I used a vacuum cleaner to clean the dust, I inserted the vacuum cleaner tip inside the case, and touched several components  with the vacuum plastic tip,
Then I did the second serious mistake – I switched the vacuum cleaner to “Blower mode” and I pointed the air directly to the Fans – this caused the fans to  spin really fast (at the moment I did not take into consideration that the fans spin create current and that sure not a good thing)

After I finished with the "cleaning process”, I closed the lid, plugged the computer, and guess what - the computer was dead.
The PSU was ok and the computer switched on but displaying nothing more than a black screen, even no "Beeps" from the motherboard.
Later on I discovered that my HDD and my motherboard went dead.

I began to read about ESD and I realized that my actions included all the stuff that one should not do when cleaning a computer. 

I read this post about ESD
https://www.eevblog.com/forum/beginners/esd-!!!!/msg146753/#msg146753

and I have some questions:

1)  I bought a cheap wrist strap (link below) - Where do I need to connect the alligator to ? is it ok to connect it to a piece of steel or cooper ?
http://dx.com/p/anti-static-retractable-wrist-strap-band-with-clamp-black-80642

2)  Is there any "Coulomb meter" that I can buy?

3) Could someone recommend me which ESD mat I should buy - I am looking for something small, and not too expensive.
    take into consideration that I’m working with Arduino electronic and stuff like that.

4) What is the best method to avoid ESD while dealing with computer components?


Thanks,
Guy

[GreyWoolfe]

Guy, first off, don't worry about your English, it is just fine.  Clip the wrist strap to the computer chassis.  I have been servicing computers and printers (for a living)since 1999.  In that time, I have never used a wrist strap, used magnetized screwdrivers to remove parts including hard drives and motherboards and use canned air regularly to clean out all the computers here.  I have never fried anything.  I am not sure just what happened to blow your computer.  Does your vacuum have an earth grounded pin on the plug?  If not, that could be part of the problem.  If so, is the outlet properly grounded.  Inexpensive testers can be bought to check the outlet.  I blow out the fans, including the psu fan with the canned air, that shouldn't have caused any issue.  Is the air in your house warm and dry?  Those conditions can cause static build up and can be part of the problem.  Let's see what anyone else contributes.

[rexxar]

Blank screen with no beeps sounds like a CPU issue. I would check the capacitors around the processor. Sometimes you get a cheap board, and the caps dry up and swell. All it takes is for you to move it, and it dies completely, taking out power for the CPU. This happened to me moving a computer from house to house. I would definitely try to reseat the processor and RAM.

If your HDD is truly dead, as in won't even spin up, try checking for continuity between the power rails and ground, you may have tripped the protection diode (TVS, I think?), which would short the rails, taking the PSU down. Does the system power up with the HDD disconnected? You said PSU was okay, so all the voltages check out?

Forced air shouldn't cause any issues, I mean, that's how your computer is cooled. Compressed air is really the best way to clean a computer.

[Rerouter]

a good recommendation, for later is to leave the power cord in but switched off at the back of the psu (not the red voltage selector switch) as this provides a constant ground path,

it is true that its not wise to spin fans with the computer turned off at high speeds, though (and this depends on the manufacturers quality) it should rarely be able to kill anything more than the fan control IC.

equally i have many many times assembled, repaired and cleaned computers on my carpeted floor, without frying anything (maybe took a year off a RAM chip but nothing dead when assembled) though for cleaning i do use a cheap compact air compressor which as a double edged sword does hold moisture so static can never build up.

rexxar your thinking of a MOV, in most cases a TVS diode doesn't short out, it just shunts the surge to ground with a much higher rating than a normal diode.


and if you still have that computer kicking around, try a cmos reset (leave plugged in, but switch off at back, press the power button to discharge the psu, remove the clock battery for a minute (if no visible battery there is normally a clear_cmos jumper somewhere near the bottom left) then throw it back in, turn back on, wait another minute then turn it on and see if it does anything,

this resets the motherboard to default settings, i have had motherboards that get corrupted when unplugged for a while due to a half dead battery.

[rexxar]

rexxar your thinking of a MOV, in most cases a TVS diode doesn't short out, it just shunts the surge to ground with a much higher rating than a normal diode.

No, It's a TVS. Under extreme conditions like prolonged overvoltage, they'll fail short to protect the rest of the circuitry. Hard drive controllers might have MOVs or other ESD protection, but I'm not too familiar with them, so I don't really know.

[pickle9000]

By chance does the vacuum cleaner have a plastic hose / fan and is ungrounded? 

[AndyC_772]

Always make sure your plastic hoses are grounded...! 

I doubt this particular PC died because of ESD. My money would be on one of the fans spinning up, acting as a generator, and feeding a high voltage into the tacho sensor pin on the motherboard.

Rather than re-invent the wheel, here's a mildly informative rant I posted on another forum a few years ago, in response to someone asking about how to handle a DRAM module when fitting it. I hope you find it useful.

ESD is a subject which is very poorly understood, even in the electronics industry where people should know better. Spare me a few minutes and I'll clear up a few misunderstandings that'll hopefully save you an expensive repair bill one day.

First off, a few things you may already know about ESD:

- Your DRAM is designed to work off 2.5V or less. Walking across a carpet can generate voltages in the order of 5,000V or more.

- Rubbing two insulators together (eg. two layers of clothing) causes static electricity to be generated, by transferring electrons from the surface of one to the surface of the other

- Static electricity that's just sitting there on the surface of an insulator isn't doing any harm. What causes damage is when that electricity is suddenly allowed to flow from one place to another via a conductive path. At the moment the conductive path is formed, the instantaneous current can be huge, and if your SSD (Static Sensitive Device - could be a DRAM module, CPU, motherboard - anything with exposed electronic components) is in that path, it can be damaged.

- The discharge current causes a heating effect, just like when you connect the mains to an electric fire. Too much heat in a small device burns it out, it's that simple. The smaller the device - a transistor, for example - the more sensitive it will be to ESD damage.

And a few things you probably DIDN'T know:

- You DO NOT have to actually touch a Static Sensitive Device (SSD) such as a DRAM module in order to damage it. Merely passing your hand near it can be enough.

- An ESD event can be strong enough to cause damage well below the threshold where you'll feel it - so you can destroy a device without even knowing it.

- A device damaged by ESD DOES NOT necessarily stop working straight away, but its performance and lifetime can be drastically reduced. So, just because you put a machine together and it seems to work DOESN'T mean you've got away with it.

- An SSD enclosed within a conductive anti-static bag is NOT completely immune to ESD damage, because although it's protected from electric fields, it's not protected at all from magnetic fields. A spark outside the bag causes a rapidly changing magnetic field, which can induce a current in any conductor inside the bag. (Think: that's how a generator works!)

- the correct way to package an SSD is to put it within a conductive bag, and then to package that bag in a reasonable thickness of 'pink' bubble wrap or other packaging. The bag protects against electric fields, and the pink material provides enough physical space around the SSD that large magnetic fields (from sparks) can't be generated physically close enough to cause damage.

- 'pink' packaging material is coloured that way by the manufacturer to indicate that it's made so that rubbing against it doesn't produce a charge. It is NOT conductive and it does NOT protect equipment from electric or magnetic fields. It is, however, the correct material to use to package SSDs that are already enclosed in conductive bags.

- the pink colour is just an identifier. Retail boxed CPUs, for example, come in clear plastic because it looks nice, but that's OK - Intel & co know what they're doing.

Be aware, though: an awful lot of PC component vendors DO NOT know the correct way to package an SSD. If you order a component, such as a CPU or memory module, and it's not correctly packaged, you'd be within your rights to send it back - IMHO, of course

So, with all that in mind, what can you do to protect your equipment?

In order to damage a component, you need a potential difference between the component itself and the thing you're going to touch it with. No PD = no current = no damage.

So, normal practise in an electronic assembly plant is to ensure that everything is at the same potential all the time, and that means:

- everything is conductive: bench, floor, tools, lab coat, even the waste paper bin. Unnecessary insulating materials (crisp packets, coffee cups etc) are banned from assembly areas.

- everything conductive is grounded - NOT because there's anything 'magic' about ground, but that it ensures everything in the plant is at the SAME potential as everything else.

- conductive materials used still have some resistance - they're not made of good conductors like copper and aluminium, but instead they use carbon loaded rubber or plastics. This ensures that when a potential difference does exist, the current involved is small and safe. Charge leaks away relatively slowly rather than suddenly.

These basic precautions mean that everything the SSD's are likely to touch are at the same potential; no difference in potential = no current = no damage.

So, assuming you don't have all that kit, what can you do to protect your equipment?

- borrow the correct equipment! There really is no substitute for a dissipative bench mat and a wrist strap. Really! If your PC packs up in 6 months' time and you didn't use the proper equipment, you only have yourself to blame.

...but if that's simply not possible...

- on a desktop PC, DO plug it into the mains, but turn off the power at the wall - you only want the earth connection. (Disclaimer: safety, safety, safety!!! If you're not absolutely 100% sure about the implications of this, get someone else to upgrade your PC for you! I am NOT RESPONSIBLE for anything YOU CHOOSE to do with your PC, REGARDLESS of whether YOU CHOOSE to treat my comments as advice or instructions!).

- don't wear nylon or other synthetic fabrics - wear cotton instead. Or do the upgrade naked if that's your thing! But whatever you do, don't pull a sweater off over your head and THEN grab your shiny new DRAM module. All those little clicks you heard when you pulled the sweater off were ESD events - you're now charged up to 10,000 volts and your DRAM is doomed/

- touch the EARTHED bare metal case of your PC.

- touch the silver or black bag that your DRAM comes in to the bare metal case of your PC as well. There's no point in you being earthed if the SSD is charged up to 10,000V when you get it.

- The moment you first touch the SSD after opening the conductive bag is the moment at which you're most likely to damage it, because you don't know what potential it's at. Get this into your head! A proper wrist strap contains a 1MOhm resistor to limit the current that'll inevitably flow through your shiny new DRAM when you first touch it. If you had a proper wrist strap on now, you wouldn't be about to risk blowing it up. Now is the time to decide NOT to open the bag today, and to pick up a wrist strap for a few quid off Ebay.

- Remove the module from its bag and install into your PC. Try to maintain a finger or elbow in contact with the chassis of your PC at all times, it only takes a moment to 'recharge' once you let go!

- Reassemble your PC and test.

Finally, be aware that there's some scarily bad misinformation around about ESD. From this very thread:

- "It doesn't matter, I've never had a problem" - see above. You can damage a module without realising it, and the damage may not show up for months. Now you know that this 'latent damage' can occur, you'll be in a better position to put 2+2 together when your PC 'inexplicably' packs up next year.

- "Touch a metal object" - pointless. You need to ensure that you, your PC and the component you're installing are all at the same potential. If it's plugged in then your PC is at earth potential, so if you touch a metal water pipe (something which is connected to earth and, therefore, at the same potential), then that's good. But touching a door handle just makes you look stupid.

- "Latex gloves" / "rubber" - ?! You're not trying to protect it from some biological infection - latex is an insulator and can therefore hold a charge. It's probably the worst thing you could possibly do from an ESD point of view. (Sometimes workers in a clean room use them to avoid contamination, but that's not the problem in this case).

- "One hand in the back pocket" - is a good rule for personal safety if you're working on live equipment, because if you touch a live conductor it helps prevent current from passing through your chest. But your PC is switched off at the wall. Right answer to the wrong question. Ditto for insulating boots - workers in ESD protected areas wear conductive heel straps, and NEVER work directly on live equipment.

- "Switch on after removing the battery to discharge the equipment" - wrong again. This has nothing to do with ESD, it's to ensure that the power supply caps in the PC have drained. All you need do is wait 10 seconds after switching off and you'll be fine. This has nothing to do with static.

Hope that helps!!

Andy.

[IanB]

In addition to what others have said, I would mention that a powerful vacuum cleaner with a plastic nozzle is indeed a static generator. The friction of the air rushing over the plastic nozzle causes a static charge to build up on the surface (which is why dust tends to stick to it in use).

So it probably is not a good idea to go waving a vacuum cleaner nozzle inside sensitive electronic equipment like a computer. When I do a dust clean I try to use a gentle setting with a brush attachment and I keep it way from the circuit boards. I just tend to clean fans and grilles where the dust accumulates and use a soft hand brush to loosen dust in the corners and other places so it can be sucked up.

[guyaros]

Guy, first off, don't worry about your English, it is just fine.  Clip the wrist strap to the computer chassis.  I have been servicing computers and printers (for a living)since 1999.  In that time, I have never used a wrist strap, used magnetized screwdrivers to remove parts including hard drives and motherboards and use canned air regularly to clean out all the computers here.  I have never fried anything.  I am not sure just what happened to blow your computer.  Does your vacuum have an earth grounded pin on the plug?  If not, that could be part of the problem.  If so, is the outlet properly grounded.  Inexpensive testers can be bought to check the outlet.  I blow out the fans, including the psu fan with the canned air, that shouldn't have caused any issue.  Is the air in your house warm and dry?  Those conditions can cause static build up and can be part of the problem.  Let's see what anyone else contributes.

Thanks for the compliment regarding the English, I am trying to be as clear as possible.

Regarding the vacuum cleaner - I'm using this vacuum cleaner:
http://www.karcher.com/int/Products/Home__Garden/Vacuums/Wet_and_dry_vacuum_cleaners/16296500.htm
It is grounded, and off topic it is super recommended vacuum cleaner, it is very powerful and heavy duty, better than any Dyson I encounter.

I read that one should never use a vacuum cleaner to clean off dust from a computer, because:
Vacuum cleaners nozzles are made from plastic, in conjunction with that fact that the air flow cause to a static buildup of charge.
The charge is prone to accumulate on the nozzle because plastic is non-conductive so the buildup can reach to high voltage.
this static charge can defently cause to ESD to the computer components, even if the nozzle is not touching any computer components, the electric field that the static charge generate can cause ESD, so using from a "safe" distance is not safe, because one cannot predict what is safe distance.

As you mentioned - The best method for cleaning dust from a computer is to use the spray can.
This spray can should be used with a short bursts in order to prevent moisture that can cause other type of damage (Corrosion).

It is also important to prevent from the fans to spin.
Use a tooth stick or something else to prevent the fans from spinning.

The spinning will generate a current (if it goes to a diode I don’t know - I know it should) and this current is defiantly not good for the system.
Plus the air flow cause the fans to spin super-fast, it can reach well beyond the fans RPM limit, so this can cause to a bearing wear.

Regarding your question about moisture - Currently its winter in my country, and at the day I cleaned my computer, it was a rainy day, so no dry air at all.
Plus I did not use the air-con at the time, and the door (to outside) was wide open when I cleaned my pc.
I do not have a carpet, and I did not wear any nylon clothes.

a good recommendation, for later is to leave the power cord in but switched off at the back of the psu (not the red voltage selector switch) as this provides a constant ground path,


and if you still have that computer kicking around, try a cmos reset (leave plugged in, but switch off at back, press the power button to discharge the psu, remove the clock battery for a minute (if no visible battery there is normally a clear_cmos jumper somewhere near the bottom left) then throw it back in, turn back on, wait another minute then turn it on and see if it does anything,

this resets the motherboard to default settings, i have had motherboards that get corrupted when unplugged for a while due to a half dead battery.

It is indeed good recommendation.
At the time I cleaned my PC,  I don’t think I followed that recommendation (I was not familiar with).
This is also the purpose of this thread - to warn others from getting their expensive equipment from damage.

I still have this motherboard, I am storing it for future investigation or just for taking it apart and practice soldering.
Maybe I’ll send it to “Dave Mailbag” , will see about that.

By chance does the vacuum cleaner have a plastic hose / fan and is ungrounded?

I did not fully understood what it means.

Rather than re-invent the wheel, here's a mildly informative rant I posted on another forum a few years ago, in response to someone asking about how to handle a DRAM module when fitting it. I hope you find it useful.

Hi Andy,
I already mentioned that I read your post, before I started this thread.
It is indeed very informative, and I would like to thank you for that.

[amyk]

I've seen a lot of computer shops here use vacuum cleaners to clean PCs, and they'd have to eat the damages otherwise, so I don't think it's that big of a deal. I clean mine with vacuum + moist towels too. The moisture could have a lot to do with it though, and the fact that I'm holding the snout with one hand while the other hand sits on the grounded case.

[BravoV]

Given most household vacuum cleaner have plastic nozzle and the flexi-hose, regarding static generated while sucking air, will it help if we somehow wrap the nozzle with wires or metal foil firmly and make it connected to gorund ?

[guyaros]

Given most household vacuum cleaner have plastic nozzle and the flexi-hose, regarding static generated while sucking air, will it help if we somehow wrap the nozzle with wires or metal foil firmly and make it connected to gorund ?

I don’t think it’s possible to ground plastic parts.

Even if you ground single point on the plastic, there are still other points on the plastic that contain static charge due to the fact that the electrons cannot flow in plastics so one point can contain large amount of charge and other point contains nothings.

Maybe if you wrap the plastic nozzle with metal wire and ground the wire.