ESD questions, newbie introduction, PC cleaning warning - Page 1
Forum section: electronics / beginners

author: guyaros
author_rank: Newbie
timestamp: January 02, 2014, 12:24:08 am
content: HelloMy name is Guy, I am a student forMechanicalengineering 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 caseAnd 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 ESDhttps://www.eevblog.com/forum/beginners/esd-!!!!/msg146753/#msg146753and 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-806422) 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

author: GreyWoolfe
author_rank: Unknown
timestamp: January 02, 2014, 02:23:55 am
content: 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.

author: rexxar
author_rank: Frequent Contributor
timestamp: January 02, 2014, 02:49:24 am
content: 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.

author: Rerouter
author_rank: Super Contributor
timestamp: January 02, 2014, 03:55:34 am
content: 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.

author: rexxar
author_rank: Frequent Contributor
timestamp: January 02, 2014, 04:38:13 am
content: Quote from: Rerouter on January 02, 2014, 03:55:34 amNo, 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.

author: pickle9000
author_rank: Super Contributor
timestamp: January 02, 2014, 04:59:59 am
content: By chance does the vacuum cleaner have a plastic hose / fan and is ungrounded?

author: AndyC_772
author_rank: Super Contributor
timestamp: January 02, 2014, 08:24:05 am
content: Always make sure yourplastichoses 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.Quote from: me, a long time ago, in a galaxy far, far away

author: IanB
author_rank: Super Contributor
timestamp: January 02, 2014, 09:52:11 am
content: 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.

author: guyaros
author_rank: Newbie
timestamp: January 02, 2014, 10:44:53 am
content: Quote from: GreyWoolfe on January 02, 2014, 02:23:55 amThanks 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.htmIt 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.Quote from: Rerouter on January 02, 2014, 03:55:34 amIt 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.Quote from: pickle9000 on January 02, 2014, 04:59:59 amI did not fully understood what it means.Quote from: AndyC_772 on January 02, 2014, 08:24:05 amHi 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.

author: amyk
author_rank: Super Contributor
timestamp: January 02, 2014, 12:33:49 pm
content: 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.

author: BravoV
author_rank: Super Contributor
timestamp: January 02, 2014, 12:49:48 pm
content: 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 ?

author: guyaros
author_rank: Newbie
timestamp: January 02, 2014, 01:38:41 pm
content: Quote from: BravoV on January 02, 2014, 12:49:48 pmI 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.