DIY

Is your service bench static safe?

Lax precautions against electrostatic discharge can reduce the effectiveness of your support team. Here's a checklist to help you set up an ESD-safe workshop.

Lax precautions against electrostatic discharge can reduce the effectiveness of your support team. Here's how to set up an ESD-safe workshop.

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If you do any component-level service in your support shop, you should have at least one static-safe workstation. A tiny static discharge can hit a printed circuit board like a lightning strike, critically damaging the component. Protecting the systems you work on from the hazards of electrostatic discharge (ESD) requires only a little forethought and a small investment, but the effort is worth it. Here's your checklist for building a static-safe workspace.

Ground/polarity tester

This is the first tool I use when verifying that my working environment is ESD-safe. A ground/polarity tester plugs in to an electrical outlet and can help you verify that the outlet is wired correctly. Most of the other static-safety devices that you'll want to use are going to rely on the your grounded outlets to dissipate charge effectively, so testing your outlets is very important. Don't build on a shaky foundation; make sure that the outlets in your service center are properly grounded before you start working in the space.

In the field: A ground/polarity tester is also easy to carry in a mobile tool kit and can be used to verify that the outlets your users are plugging in to are trustworthy. I've seen a couple of instances where intermittent PC instability was eventually traced back to an improperly wired power outlet. Antistatic mat

Covering your work surface with an antistatic mat ensures that you'll always have a proper place to service sensitive components, even if you're not blessed with having expensive shop furniture. The purpose of the antistatic mat is to let any residual charge flow across the mat surface and away from the items you're working on. To accomplish that, your mat should include a ground lead that can be attached to a properly grounded outlet. While on the subject of mats, one ESD safety protocol that is important not to overlook is mat maintenance. Quality static mats will have a soapy finish to them that will help static "flow" to the ground. This finish can be maintained by using cleaners that are specially designed for antistatic mats. Taking care of your work surface will help it last longer and will more effectively protect your components.

In the field: Any tech doing on-site service that would require handing static-sensitive items should have a small mat that they can roll up and take to a remote location. Grounding strap

An antistatic grounding strap is used to make sure that the technician doesn't pass any charge to the components he is working on. Grounding straps take two basic forms: the wrist strap and the heel strap. The simplest wrist straps have a lead that ends in an alligator clip, so you can ground yourself directly to a machine's chassis. Other wrist strap systems are designed with a lead that can be connected to a grounded bench mat. Heel systems rely on the premise that the tech will have a grounded floor mat to stand on.

In the field: A wrist strap system will be easier to take on the road with you, if only because you won't have to worry about carrying a floor mat.

These three items are the core of any static-safe work environment. There are some other things you should have on hand before beginning serious work with static sensitive components, though. First, stock up on static-shielded bags of various sizes to use for storing components. Second, a ground wire with alligator clips at both ends is useful for grounding specific components or tools to your work area. Finally, get some training on electrical safety. Devices intended to protect your computer components from electrostatic discharge can actually put technicians at risk when used in the wrong situation.

Make sure you're never grounded when you work on plugged-in equipment or when you handle high-voltage components that have not been discharged. Be particularly wary of CRTs and power supplies. The capacitors in those devices can pack a nasty charge, even after being disconnected from current. Remember, your static-safe work area will protect your components, but it's your training and your caution that will ensure your health.

59 comments
JackOfAllTech
JackOfAllTech

As long as you leave the PC plugged in (careful what you touch) and don't move your feet after you've grounded yourself, there's really nothing to worry about. In almost 20 years, I've never had a single static discharge while working or handling anything.

l_creech
l_creech

I always carry at least 2 ESD mats and associated straps with me for field work. Even with those I refuse to work over a carpeted area, and insist on having a linoleum surface to work over, preferably a kitchen or kitchenette where I can discharge the mats to the plumbing system (cold water inlet is my preference unless the building electrical is grounded here). In my shop I have an isolated grounding rod for a true earth ground that my mats are connected to. For system cleaning I agree that canned sprays are probably the safest route if you don't have one of the 3M (or similar) vacuums that are made for working on electronics.

PVBenn
PVBenn

Thanks for the refresher. I was a Tech back in the 80's and the company I worked for implemented antistatic workstations and in one week saw the return rate on defective computers drop 90%. What is surprising is the number of Techs I still see who know but don't wear anti static wrist straps. The one Tech I will let work on my servers showed me something cool last year, a wireless wrist strap. Researched it and it looked legit, the servers he built are still running without a problem to date so it really must work.

NickNielsen
NickNielsen

And the two sentences before that: [i]Finally, get some training on electrical safety. Devices intended to protect your computer components from electrostatic discharge can actually put technicians at risk when used in the wrong situation.[/i] Nothing scares me more than watching an "experienced" computer technician connect his anti-static wrist strap to a PC while it's still connected to an outlet.

Michael Kassner
Michael Kassner

My IT and telecom (amateur radio op) experience started way before transistors and ICs were even invented. That said, I have yet to use a ground strap. Still, I have not blown anything up and I am by no means lucky.

mmoran
mmoran

That ground lead with the alligator clips should have a 1-megohm resistor inline. Commercial ESD accessories such as wrist straps, heel straps and static mats have them for two very good reasons: 1) ESD damage is related to the magnitude of current flow. The idea is to *drain* any static charges, not to *dump* them. Simply moving around in normal everyday clothing can generate static charges of thousands of volts. When you get zapped touching that metal doorknob in winter, that's a couple thousand volts right there, believe it or not. 2) Suppose that one end of that clip lead or wrist strap cord accidentally comes into contact with power line voltage. Would you rather have a straight-through connection, or a nice big resistor between you and the volts? 'Nuff said. Do yourselves and your customers a favor- spend a little time to come up to speed on ESD prevention: http://www.esda.org/basics/part1.cfm And thanks to William Jones for raising the topic.

mike
mike

I'm gonna get chastized here but I'm just posting my real world experience. I've been working on PC's now for 13 years. In a shop for a time we used static straps while installing memory, remeber when 4 Megabytes cost a small fortune? But we didn;t use it for much else. The benches did have anti static mats on top that were grounded. In my current shop I have an antstatic mat but that's it. I have worked on everything and never had a problem, but I do take basic steps to make sure I have grounded, discharged my body before digging in. Now with that said the only devices I have ever had a problem with are modem cards. I have killed a few in the years, they seem to have a real sensitivity to static, as a matter of fact I was in a bind to put one in just this week and it was installed in a PC in the back of the car. I yanked it out on a very windy day and then took it in to another PC. Yup it was fried. But I will say from my experience that for the most part antistatic measures just seem to be a bit of over kill in the real world. Now that's just me and I'm not saying I'm against it or you shouldn't take precautions. MIke

NickNielsen
NickNielsen

When you do, there is power to the motherboard. The companent you are installing or reseating may have power to it. Unplug the PC and equalize your potential with the PC chassis. This will greatly reduce the chance of ESD.

pgroenenstein
pgroenenstein

Having worked extensively in the Elevator industry where safety and reliability is a major concern, I can only state that certain rules are there because they have been tested and proven overtime.We were drilled into how to handle static sensitive devices. And you might think that your not zapping anything, when in reality you are more likely than not sending small charges through your clients valued components. This is what makes the diff between a good techie and a great techie! Grounding is not a once off reward it'S an INVESTMENT that would pay off over time.

zackers
zackers

Leaving your PC plugged in adds nothing in preventing static shocks. The critical point is that you want to reduce the voltage difference between you and the equipment you are working on. Also, small discharges happen all the time, but you don't want them to occur at a sensitive component, which is what happens when you and the equipment are not electrically connected before you touch components inside the equipment.

beechwoodf
beechwoodf

Nothing like a dc charge as it burns various parts of the body! I too, date to tubes and ham radio. Most of us from that eraare scared of the thouht of becoming a "crispy Critter"

Michael Jay
Michael Jay

where is your adventurous spirit, there is nothing like being electrocuted early in the day. Something about the warm buzz of 60 hz going thru your body, vibrating the body like a leaf in a hurricane. Just Kidding.

oldbaritone
oldbaritone

"Fire Bottles" don't mind high voltage, and they're hardly-if-ever sensitive enough to be damaged by static. Almost indestructible. Not so with solid state. Maybe you've been using the "hold on" method. Maybe you always wear cotton. Maybe your floors, benches and work stations are all wood. Maybe it's always humid where you are. And maybe you can play Russian Roulette 1,000 times without getting your brains blown out. But it's not the way to bet. Ditto ESD - from another ham who thought the same thing, right up until I blew a $500 processor chip by handling it without ESD protection. I proved I was both. Once burned, twice careful. AA2CO

davidt
davidt

As noted earlier in the discussion (and this has been my experience as well) you may never KNOW that you have given a life-shortening bolt to a component. Of course, this didn't apply to pre-transistor tube-type technologies (and yes, I also worked on those).

rketchum
rketchum

It bleeds off the charge. When working as a test tech for Control Data, we thoroughly tested all circuit boards as systems were put together for various government projects, used in defense of ships. No room for a weak component or sailors or ships would be lost. We had AS mats, special floor wax and cleaner, work benches, straps, and even lab coats woven with stainless steel fibers to dissipate any charge. One "long time" employee carried boards in a special static bag and tub, between work stations. She didn't like the cooler room temp and one day wore a mohair sweater outside her lab coat to keep warm. During the final tests, I discovered a problem with something testing a little marginally. Tests were done at various stages of the build process. Each test is expensive because of equipment and manpower usage. She handled this particular board during the initial stages. The problem didn't show up until later the next day. All test and component installation (installed during testing phases) had to be redone. After getting the design engineers involved, we tracked down the bad component. We removed the case on the IC chip and looked at it with a microscope. It looked like a bullet hole. The total cost for one small static discharge was HUGE. That particular system board was to be used for fire control radar that automatically fired high volume, low altitude machine guns to protect Navy ships from aircraft. Many lives could have been lost if it failed during use. True, most computers aren't that critical, but a delay or glitch in a accounting computer can cost the company or employees a great deal in many ways you might not realize. They are your customers. Want to loose them because of a few shortcuts?

ray.labrecque
ray.labrecque

Static discharge seldom kills components right away, it weakens them and greatly reduces their mean time between failure (MTBF). That's the problem with PROVING that you need to be static safe, it's is time consuming to demonstrate the outcome. If you zap a clients pc, you are merely guaranteeing a return visit to the repair shop. Do them all a favor and stop ignoring the recommended protocols, strap in AND step on the mat!

mjd420nova
mjd420nova

I can't count the number of units that I have to service that have had ESD damage. One note to anyone that decides to attempt servicing or upgrading hardware their computer themselves is to NOT unplug the unit from the wall. That power cord, when plugged into the wall provides the only ground you'll find in 99 percent of peoples homes or offices. The power supply has a metal case around it and this will protect you from any lethal voltages so you will remain safe while still being plugged in. I still use a ground tester and wrist strap while on a clients site. The tester determines if the ground is valid and the wrist strap to insure I'm grounded even if the unit isn't. Modems are a particular beast because they have some transformers that can induce some rather high static charges.

Craig_B
Craig_B

Based on my experience I tend to agree with Mike. Ground yourself first then do the work. One note though, you can degrade a componet but not kill it, so it does not last as long but you will never know until it finally dies.

mmoran
mmoran

... is that ESD damage is more often "latent than blatant." Rather than being an obvious paperweight like your modem, the device is only degraded and while it still works, it fails some time in the future, much before its normal lifespan. And in a service environment, it's very difficult to trace such failures back to prior non-ESD safe handling so the condition never gets remedied. Proper ESD equipment, procedures and training are a modest and wise investment.

edge2100
edge2100

is touching the power supply to ground myself not enough when digging into a computer?

oldbaritone
oldbaritone

Unless the outlet or supply is hardwire-switched, a plugged-in PC may power up unexpectedly. Just open almost any pc cover while it's plugged in, turned off. You'll see LED's glowing. It's not like the old "0/1" tab switch of the 80's. Modern supplies run some things "hot" all of the time. The power switch is now just a control-voltage signal - and it MUST have power available to work. It's not really a "power" switch any more.

PVBenn
PVBenn

The Tech might be crazy, after reading your link I'm now very skeptical of the claim. The Tech I was dealing with had this about a year ago and at that time searching the web did not show that Article. I thought it might be too good to be true. Thanks for the info.

Walthy
Walthy

Good reference! My worst shock was a custom-built German Audio Power Amplifier that came into our shop from a traveling circus/carnival in the late 60s. Somebody had replaced a large capacitor and it stuck out through the chassis. After knocking me off my stool, I measured it at around 660Vdc from a tripler circuit. In the mid 60s in the Marine Corps I saw our sergeant (who was wearing a metal banded wrist watch) grabbed our bench radar setup and started to turn it when his watch came in contact with the magnetron high voltage circuit. He jumped backward, hit his head on the low ceiling of the field service van's air conditioner. He kept going backward and almost went out the other side. He was shaky for a couple of hours after that. In the early 70s I worked on 10kw microwave transmitters and received several shocks from various parts of those, including a small RF hole in my finger where I touched a live coax center conductor. I've purposely never worn metal rings and until recently no metal watches while working. I'm building a few machines these days, so I think I'll start taking off my watch again. Low voltage, high amperage is still not good to short out. I'm also going to get myself a new wriststrap. What about vacuuming out dusty cases? Aside from having a very loud 3M anti-static vacuuming system some years back, what can you do. I always ground myself and hold the end of the vacuum hose to keep the static down. I made the mistake of blowing out my case with my new air compressor. I think blowing the air cause a static build up which then fried my system. I now only use canned, static-free air, or careful vacuuming while grounded. Any other suggestions?

NickNielsen
NickNielsen

Too many years of high voltage (1KV and up) power supplies and high power transmitters. But those were usually low current applications (1 amp or less) that used the voltage to provide most of the power. A live PC is quite a different animal; the currents flowing around in there can get pretty scary. I mean, not many people know that when the 5V bus is rated at 135W, that's 27 amps! And it only takes half an amp to kill!

gadgetgirl
gadgetgirl

the dolt that did work on the kitchen before we bought this house didn't remove wiring, just cut off the end of the cable, and plastered it into the wall..... still live.... HOB found out the hard way, probably because he knows, as a proper sparky, that people don't plaster in things that are still live.... oh look. HOB against opposite wall of kitchen in split second of blue light.... Him still here. Still bears grudge against dolt what did it.... :) GG

NickNielsen
NickNielsen

It's the reflex reaction causing me to punch myself in the mouth I hate. ;) etu

wsmith
wsmith

Basic safety is- You do not work on equipment that is still plugged in. Even the article you just read says, "Make sure you?re never grounded when you work on plugged-in equipment"

NickNielsen
NickNielsen

Ground is totally irrelevant when trying to prevent ESD. A ground provides a return path for the supply voltage, diverts leakage current from the chassis, and sets one reference level for the voltages used inside the equipment. What prevents ESD is eliminating the potential difference between you and the equipment you are working on. That is best done by connecting an anti-static wrist strap to the chassis or by maintaining direct contact with the equipment. [i][b]Always[/b] remove the input power from anything you are working on![/i] There are exceptions to this rule–sometimes you have to make voltage measurements–but only in rare cases.

beechwoodf
beechwoodf

I teach my students here in florida to toch the power suplly, or the bare screw on an outlet faceplate or metal face plate itself. this is usually sufficient

oldbaritone
oldbaritone

How long does it take to put on a static wrist band and clip it to the chassis? Seconds. I used to think "Just hold on" was good enough. Trouble is, sooner or later, you drop something and reach for it with that other hand. Zap!

ray.labrecque
ray.labrecque

Exactly! Nice to see someone else out there touting the truth instead of lazy-boy shortcuts~!

mike
mike

I have no argument with that and definetly aggree. Is touching the PS enough, not really, but it's better than not. Make sure it's still plugged in though or the charge has no where to go.

ray.labrecque
ray.labrecque

Every time you move you build up more static that is just looking for the quickest path to ground...

capeterson67
capeterson67

"If you have a higher or lower charge than the machine, your relative static buildup will equalize when you touch. If it's big enough, you get a spark, but damaging static can also discharge without any sensation at all." The VAST majority of the time, damaging ESD is undetected with no sensation to the human side of the ESD at all. As previously mentioned, it degraded the components rather than ruining them outright.

detours
detours

There are several problems with leaving the PC plugged in: 1. Power supplies are live when plugged in As stated in other replies, modern power supplies still power the motherboard and capacitors when plugged in. Also, since the PC is connected to live current, working on the internals puts you in direct contact with any power surges and lightning strikes. 2. Static discharge depends on voltage differential If you have a higher or lower charge than the machine, your relative static buildup will equalize when you touch. If it's big enough, you get a spark, but damaging static can also discharge without any sensation at all. 3. Being 'grounded' means zero voltage differential, not zero electrical charge Grounding yourself 'equalizes' your electrical charge with the local environment but doesn't 'eliminate' the electrical charge. For example, in an isolated environment with you and the PC on static mats, grounding yourself to the PC equalizes the relative charge between you. At the risk of oversimplifying, instead of being +4 and +8 (random values), you may equalize to +6. At that point, unless one of you somehow gains or loses a charge, there is no more electrical movement in either direction. What little that may exist between your hair and fingers can be handled by a static strap. Leaving the PC plugged in to the wall 'grounds' it to the local power grid ... true. But it's an unstable ground, full of fluctuations and problems. If the A/C, heat, microwave or toaster come on in your house, or if your neighborhood has a brownout, a lightning strike or atmospheric static from a weather front moving in, the local ground voltage will rise or fall, and your PC's static charge will too. But your personal static charge doesn't vary with the local ground, so every time you touch the PC, the voltage differential between you could have changed. If it changes with your hand on the chassis, the charge will travel along the outside of the case away from delicate components. But if it changes while your hand is inside the PC, the static will pass through and damage whatever you touch. A wrist strap won't matter because the fastest path between you and the power grid is through the component you touched.

JackOfAllTech
JackOfAllTech

As long as it's plugged in to a grounded outlet, you've nothing to worry about.

davidt
davidt

Instead, I've been using compressed air (via our maintence department). I keep my hand on the metal of both the (grounded)nozzle and the computer case all the while. Of course, the computer is both unplugged and sitting on a static pad. So far so good.

doug.cronshaw@baesystems
doug.cronshaw@baesystems

You don't have to be using high voltages for metallic watch wrist straps to give you problems. Just try discharging a car 12V system to earth through one. It will become very hot very quickly, and your wrist will become similarly hot if it is still inside the strap. Watches with such straps should be removed before working on auto electrical systems to avoid the dangers of such discharges.

NickNielsen
NickNielsen

Typed it up to keep, then lost the copy, or, more like, just haven't unpacked those papers in the last 30 years! Was surprised that was the only copy that came up on Google. ...moments later... Well, well, look what Bing found! http://stolzweb.org/tesla/other/10safety.htm This is the generic version I remember.

Michael Jay
Michael Jay

Nick, that is very good, will have to print that for the shop. Perhaps a few changes to fit the shop but it is all good.

doug.cronshaw@baesystems
doug.cronshaw@baesystems

... never mind follow them. That's why they get classified as dolts. (There's even a strong suspicion that some of the worst dolts cannot read. This leaves them with plenty of scope for all sorts of double-whammies.)

Michael Jay
Michael Jay

I do not believe that in America or for the UK building code would allow that, but since when have dolts followed code?

wraheem1972
wraheem1972

I once took a power supply from one PC and plugged it into another; as I was turning it on I went to look at the fan on the PS and boom! Sparks flew out hitting me in the face! I had a bunch of black marks but wasn't burnt. I have no clue why it happened but after reading some of these electrical mishaps I feel extremely lucky!

NickNielsen
NickNielsen

Back when I used to work on radios, the USAF had a UHF system with 2000 VDC on the plate of the output tube and a trim potentiometer you adjusted for 1.5 VDC grid bias. (Note: The bias voltage is the difference between 2000 VDC and 1998.5 VDC!) You put your test leads in the taps and used a plastic alignment tool to adjust the trimpot...right next to the test leads. Managed to get the edge of my hand up against one of the test leads once. Not a pleasant experience at all. 2000V in through the skin at the base of the little finger and out through the tip of the same finger, leaving 2nd degree burns at both ends. Owee! :_|

mike
mike

indeed, popped a 220 three phase line once that was supposed to be off! makes quite a bang. Even better was working in a 220 three phase service panel connecting the last of the ground wires while the cabinet was HOT! Electricians do this all the time. Being carful I connected all but the last one! yeah that was the one the happend to touch a buss bar! Can you say Explosion? Blinded for 10 minuets and my co workers thought I was a gonner since I flew back against the wall behind me. Tripped a 200 amp supply main.

mike
mike

Nods to that! Was working on a 500W linear power amp for a CB radio that was not discharged!!! Bammmm Large burn to the thumb!

boxfiddler
boxfiddler

Says one who has merely been lit by a socket she thought was unpowered a couple of times.

santeewelding
santeewelding

Them electrons, piled up one after another in their wave functions, and anxious to do mischief.

Michael Jay
Michael Jay

never tasted that one, but know one who had, and lucky to survive he was.

santeewelding
santeewelding

I am privileged to live to say, gets your attention, also.

Michael Jay
Michael Jay

I repaired power supplies at the component level I got the taste of real DC. For those who do not know, power supplies ramp up the input voltage usually 120vac at 60hz to about 850 volts dc before ramping them down to logic levels, this insures that the power is very clean. I managed once to sample the high voltage DC and it is very different than AC, AC vibrates you, DC burns you, lesson learned with a small but painful burn on my hand.

Roc Riz
Roc Riz

That's the University on the Corner of Lexington Avenue, and it tells me that you should ALWAYS be in contact with ground in order to discharge static electricity. However, judging from the life of most computers these days, and even though it is a small price to pay, ESD protection goes overlooked in most cases.

NickNielsen
NickNielsen

[i]Make sure it's still plugged in though or the charge has no where to go.[/i] It's not the charge itself, but the difference in potential that is the problem. The static discharge is mostly likely to be between the component you are holding and the equipment you are working on. Simply staying in physical contact with the chassis while installing the card, processor, or whatever, is usually sufficient to eliminate any potential difference between you and the equipment and greatly reduce the chance for ESD.