Static is [not] your friend - vacuuming PC?

[DaveW]

A static charge from the vacuum cleaner can STILL jump to the exposed
computer circuitry, even with the computer turned off. The computer being
grounded makes no difference. Don't do it. Use a can of compressed air to
BLOW the dust outlike everyone in the business does.

 

[Gumby]

A static charge from the vacuum cleaner can STILL jump to the exposed
computer circuitry, even with the computer turned off. The computer being
grounded makes no difference. Don't do it. Use a can of compressed air
to BLOW the dust outlike everyone in the business does.

lots of vacuum cleaners have a metal tube the attachments
go to, just ground the tube to the same ground as the
PC. Then what you're worried about above won't happen.

 

[Floyd L. Davidson]

A static charge from the vacuum cleaner can STILL jump to the exposed
computer circuitry, even with the computer turned off. The computer being
grounded makes no difference. Don't do it. Use a can of compressed air to
BLOW the dust outlike everyone in the business does.

The compressed air is just about as bad as the vacuum cleaner...
maybe even worse in some ways.

 

[Floyd L. Davidson]

lots of vacuum cleaners have a metal tube the attachments
go to, just ground the tube to the same ground as the
PC. Then what you're worried about above won't happen.

Static charge on the nozzle is not the only problem. The buildup
of static on the various components as a result of blowing dry air
on them is just as serious as the nozzle (same source of charge!).

 

[Robert Redelmeier]

For what it's worth... Bob Pease, a respected designer at
National Semiconductor and author of a number of very useful
books including "Troubleshooting Analog Circuits", swears by
the use of a dishwasher for cleaning PC boards especially
for high-impedance, low-leakage circuits. He mentioned
the use of a "standard load of Calgonite" as the cleaning
agent... run 'em though the wash cycle, take out after the
rinse, shake off excess water, and allow to air-dry.

Pease comments that after this sort of treatment, leakage
currents across the board surface were often lower than
could be achieved using an expensive commercial solvent-based
PC-board-washing system.

Useful data! I have little doubt that a diskwasher can
get boards extremely clean.

For what it's worth, the Calgonite MSDS lists sodium
tripolyphosphate, sodium silicate, sodium carbonate, and
sodium sulphate. No hypochlorites.

Ah, that helps a bit. Hypochlorite is nasty on copper (verdegris)
and other metals. The other goodies will make for high pH,
but that usually won't do more than frost over aluminum and zinc.

-- Robert

 

[Alexander Grigoriev]

For example, gold-plated glassware/chinaware should NOT be put to
dishwasher. I wonder if it's because of the detergent.

 

[do_not_spam_me]

Anybody have any good experiences cleaning IBM Model
"M" keyboards in a (soapless) dishwasher?

The key matrix is made of 2 separate flexible circuit boards attached
together around the edges, similar to matrixes found in NMB keyboards,
including the Microsoft Natural, and moisture can remain trapped
between them. Normally you can remove those flexible boards and dry
them out enough with 90%+ alcohol, but IBM put them between a hard
piece of plastic and a sheet of metal "riveted" to together (ends of
plastic rods melted against the metal), which traps the moisture even
better. So you may have to cut off the rivet heads to get to dry out
the key matrix and then replace the rivets with install washers and
tiny screws.

 

[CBFalconer]

.... snip ...


Ah, that helps a bit. Hypochlorite is nasty on copper (verdegris)
and other metals. The other goodies will make for high pH,
but that usually won't do more than frost over aluminum and zinc.

Isn't hypochlorite just plain fixer from the darkroom? Which
required several hours of washing of prints.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

The web page descriptions are indeed fairly funny, if you know
what they are talking about. But I highly suspect anyone with a
limited background in Electro Static Discharge will be more
confused than not.


Yep. Quite a lot.

*Moving* *dry* *air* around is a great way to build up a static
charge on any component that is an insulator.

Hence *compressed* *dry* *air* and *vacuum* *cleaners* are not
good ideas. In fact, compressed air might be worse because it
can forcefully blast dust into places it wouldn't otherwise go.

If you get enough charge (a few thousand volts, for example, is
common), it will then break down the insulation between the
charge and the next nearest object that is either also holding a
charge or is able to dissipate the charge (e.g., a conductor).
The current flow when that happens is what kills your computer.
And it isn't just that specific current, but also any current
induced into other conductors as a result of that current.

The way to get the dust out of a computer case safely is to use
a damp rag to manually pick up dust. It shouldn't be so wet
that it drips moisture (though that isn't necessarily bad
either, see below), but needs to be damp enough that dust will
stick to it and static cannot build up on it. I personally
prefer to have a large bowl of water mixed with a little
household cleaner (such as 409 or Mr. Clean), in which the dust
rag (a well worn bathroom wash cloth or a thin dish towel, is
nice) is washed as it get dirty. The soapy water in the bowl
should be changed somewhat regularly too, i.e. when it gets so
dirty that as much dirt moves from the water to the rag as from
the rag to the water!

Which type of soap to use does make a difference. The idea is
something that will dissolve any grease film or other coating
that might be present, but even more important is that it be a
good water dispersant. Automatic dishwater soap is perhaps the
best in that respect.

Note that there aren't many things which can actually be damaged
by water itself. Disk drives or CRDOM/DVD drives (things with
moving parts) can be damage by water. But keyboards and
motherboards can be totally immersed in water without damage.
Any time that a system is *really* dirty, or is taken apart for
other reasons, it makes sense to literally wash the device in a
kitchen sink with a solution of soapy water, and then rinse it
off with a water spray if you have one of those handy spray
hoses meant for cleaning dishes.

You've gone just plain NUTS. I have to replace a few keyboards every
month because some bozo spilled a bottle of Dasani water in it. Coffee
is even worse. The little rubber dimples in the rubber pad collect the
water, and they will *never* dry out unless you pull the keyboard apart
and let it dry. And the cost of labor is greater than the ten dollars a
new keyboard costs. And if you pull one apart, you may never be able to
get it back together. Don't believe me? Try it sometime with a defunct
keyboard! The really funny part of all this is the deviant behavior the
user will display when you ask him or her if they spilled something in
the keyboard. "Who, me? Never!" and I pick the keyboard up and the
wter drips out of it. Yeah, right. >:-(

Floyd doesn't tell you but he lives in an igloo in a god-forsaken part
of Northern Alaska where the ground is frozen all year long. His harsh
cleaning methods aren't recommended and are a lot of hooey, IMHO,
because the rag will damage the pins of the chips in a circuit board.
It's insane to use anything but compressed air.

If the water supply is very hard (filled with minerals) and will
leave a residue, use a final bath of rubbing alcohol. Otherwise
a very dilute solution of automatic dishwater soap is probably best.
(It will leave a very thin film of water dispersant, loaded with
water, on everything. That will help protect against static and
it will also reduce dust build up because of reduced static build
up.)

After such a dunking it takes considerable time to be sure that
the water has dried completely. In places where the humidity is
low that will happen in a day or two anyway, so just put it on
the shelf and wait. Otherwise one method is to use a kitchen
oven on warm, leave the door partially open and put the device
inside the oven for several hours.

Nuts! Totally nuts! That's an excellent way to ruin it! You'll bake
the circuit board!

But *don't* use compressed air, vacuum cleaners, plastic brushes,
or synthetic cloth to clean a computer. And don't do it on a
day when the relative humidity is 10% either.

Which is ALL the time where you live! You've gotta be _kidding_ with
this post!

 

[Floyd L. Davidson]

Floyd doesn't tell you but he lives in an igloo in a god-forsaken part
of Northern Alaska where the ground is frozen all year long. His harsh

Actually I live in one of the most exciting places in the entire
world. The name of the game is adventure, and there is never a
dull moment.

cleaning methods aren't recommended and are a lot of hooey, IMHO,
because the rag will damage the pins of the chips in a circuit board.
It's insane to use anything but compressed air.

Your remarks are interesting. Ten/fifteen years ago that was
just about the only kind of response I'd get on Usenet from
claiming one could just soak these things in plain old soapy
water and get good results. But it isn't so common these
days...

Of course I've been putting electronics into a dishwasher for 40
years now too (that right *40* years, which means it was
electron tubes, not ICs). Which makes your protest just
hilarious.

You might have noticed though, that for almost every instance
of someone saying that compressed air is the right way, somebody
else says use water. The fact is that water won't zap your
circuit boards with ESD (and compressed air *will*).

Instead of flapping your jaw about it, you might do a little
research on the subject. See if you can find out what the
significance, for example, of water is for the pink anti-static
material that you commonly see. And why it's pink.

Nuts! Totally nuts! That's an excellent way to ruin it! You'll bake
the circuit board!

Yer head's where the sun don't shine, son.

Which is ALL the time where you live! You've gotta be _kidding_ with
this post!

That is so ignorant that it is a joke:

Barrow, Wiley Post-Will Rogers Memorial Airport, AK, United States
(PABR) 71-17-07N 156-45-57W 10M
Weather reported at: Thu Oct 28 01:44:00 2004 AKDT
...
Temperature : 12 F (-11 C)
Dew Point : 8 F (-13 C)
*Relative* *Humidity* : *85%*
Pressure (altimeter): 29.63 in. Hg (1003 hPa)

-- http://weather.noaa.gov/weather/current/PABR.html

Do you understand what 85% relative humidity is? It is rather
*normal* in a place that sits on a point jutting out into the
ocean.

 

[Jim Douglas]

Give it a blowjob, take it to the garage, get your leaf blower, and blow
away!

 

[Keith R. Williams]

Isn't hypochlorite just plain fixer from the darkroom? Which
required several hours of washing of prints.

I thought "fixer" was sodium thiosulfate and some other stuff. Sodium
Hypochlorite is laundry bleach and pool chlorine.

 

[Keith R. Williams]

That is so ignorant that it is a joke:

Barrow, Wiley Post-Will Rogers Memorial Airport, AK, United States
(PABR) 71-17-07N 156-45-57W 10M
Weather reported at: Thu Oct 28 01:44:00 2004 AKDT
...
Temperature : 12 F (-11 C)
Dew Point : 8 F (-13 C)
*Relative* *Humidity* : *85%*
Pressure (altimeter): 29.63 in. Hg (1003 hPa)

-- http://weather.noaa.gov/weather/current/PABR.html

Do you understand what 85% relative humidity is? It is rather
*normal* in a place that sits on a point jutting out into the
ocean.

What's the RH after you've heated the air to, say, 68F? ;-)

Lesse...

Actual Vapor Density
-------------------- = RH
Saturation Vapor Density

At 14F (close enough) the saturation vapor density is 2.36g/m^3, so
your actual vapor density is: .85 * 2.36g/m^3 or 2.01g/m^3

Raise that air to 68F (saturation density = 17.54g/m^3)


2.01g/m^3
-------- = 11% RH
17.5g/m^3

....seems pretty dry to me. ;-)

 

[Robert Redelmeier]

That is so ignorant that it is a joke: Barrow, Wiley
Post-Will Rogers Memorial Airport, AK, United States (PABR)
71-17-07N 156-45-57W 10M

Weather reported at: Thu Oct 28 01:44:00 2004 AKDT
...
Temperature : 12 F (-11 C)
Dew Point : 8 F (-13 C)
*Relative* *Humidity* : *85%*
Pressure (altimeter): 29.63 in. Hg (1003 hPa)

Do you understand what 85% relative humidity is? It is
rather *normal* in a place that sits on a point jutting
out into the ocean.

Floyd, I realize you've been unjustifiably flamed, but that
is no reason to reduce your own credibility by misleading
statements.

Yes, arctic outdoor air usually has high relative humidity.
It has to be, otherwise the snow would sublime.

But that outdoor air is extremely dry in absolute terms.
My psychrometric chart gives 5 grains water per lb dry air for
8'F dewpt. Heated to 60'F, that is 6.4% relative humidity.
You're gonna need big humidifiers and all the fun they are
to maintain (salt build-up, ugh!)

Furthermore, I suspect that static build-up is more a function
of absolute humidity than relative humidity. Do people have
lots of static problems in Phoenix summers?

-- Robert

 

[Floyd L. Davidson]

....

Floyd, I realize you've been unjustifiably flamed, but that
is no reason to reduce your own credibility by misleading
statements.

You also have to realize that I didn't get off the boat here
yesterday. And that *you* have little to no exposure to Arctic
conditions and like a lot of other people your imagination is
good, but doesn't match the reality of Arctic living nearly as
closely as you think.

Yes, arctic outdoor air usually has high relative humidity.
It has to be, otherwise the snow would sublime.

It doesn't????

Now we've had more than one person claiming the relative
humidity in the Arctic is always low, and you claiming it is
always high. I assure you all that it isn't *necessarily*
either, and that in fact it is fairly easy to experience both
conditions in the Arctic.

But that outdoor air is extremely dry in absolute terms.
My psychrometric chart gives 5 grains water per lb dry air for
8'F dewpt. Heated to 60'F, that is 6.4% relative humidity.
You're gonna need big humidifiers and all the fun they are
to maintain (salt build-up, ugh!)

However, if you have *ever* experienced 6% relative humidity,
you know that static just crackles out of everything. You can't
move without generating a charge. Everything you touch gets
zapped. You can't pet the cat, because it will run when you
so much as look at it.

Now, I'm not going to figure out what's wrong with your
calculations, but I have a cat and it jumps on my lap and gets
petted with regularity. So far today we haven't had even one
experience of enough static buildup to cause us to zap each
other (at this temperature, it does happen, though not often).

You can be assured that the relative humidity inside my house is
*not* 6%, or anything close to it.

Furthermore, I suspect that static build-up is more a function
of absolute humidity than relative humidity. Do people have
lots of static problems in Phoenix summers?

Which is to say, you don't have any experience with this at all,
but you're willing to attempt definitive statements??? Tsch
tsch.

I lived in Tucson AZ as a teenager. Trust me, in Phoenix they
have *lots* of static problems in the summer!

I spent 20 years living near Fairbanks AK too.

In Fairbanks the relative humidity can be very low. (However,
at the moment... it's 17F and RH is 91%!) But in Fairbanks
there is no source for water vapor /and/ it is commonly -40C or
colder. Fairbanks sits inland several hundreds of miles, right
between two of the largest mountain ranges in North America;
hence the relative humidity is commonly low, with no wind, and
in the winter there are extreme cold temperatures on a regular
basis. Static is a *big* problem when it gets cold, and only a
small problem with it isn't that cold.

Barrow of course is a maritime environment, and with an ocean on
three sides and with a constant wind there is no lack of humidity.
The relative humidity for outside air is rarely ever very low,
mostly because we rarely ever get extreme cold temperatures here
(due to the moderating effect of the Arctic Ocean and the
constant wind).

The effect is that in Fairbanks static is an almost constant
problem, summer and winter, but in Barrow static is rarely a
problem except during extremely cold weather in the winter (and
virtually never during the summer).

Here are some interesting numbers. I've been archiving hourly
weather summaries from NOAA since last winter. I don't get
every hourly report each day, but in nearly 11 months have 6303
records. A quick grep produces the following numbers:

Total records: 6303
100% RH 354
90-99% 1588
80-89% 2256
70-79% 1872
60-69% 214
50-59% 18
40-49% 1

No records indicated less than 45% relative humidity.

I should probably point out that after 2 decades living in the
Interior, I have a few habits regarding static that are useful.
I use an anti-static mat on the floor and the table my computers
sit on have a grounded metal strip running down the front, such
that as I sit here typing, both of my arms are grounded.

And of course one of the reasons I advocate the use of water
solutions with a wetting agent for cleaning circuit boards is
because of the anti-static benefits (which include the effects
of having a film of wetting agent left on the circuit board to
help dissipate any static buildup, a beneficial effect that lasts
for months).

Incidentally, if anyone can find information on how the
ubiquitous pink anti-static plastic came to exist, the above
reference to leaving a wetting agent on the surface of washed
components has an interesting connection, historically. The
idea of mixing a wetting agent into the plastic mix came as a
result of observing that poly-plastic containers attracted less
surface dirt when they were *not* rinsed clean of soap after
washing. The same applies to computer motherboards.

 

[Floyd L. Davidson]

What's the RH after you've heated the air to, say, 68F? ;-)

Lesse...

Actual Vapor Density
-------------------- = RH
Saturation Vapor Density

At 14F (close enough) the saturation vapor density is 2.36g/m^3, so
your actual vapor density is: .85 * 2.36g/m^3 or 2.01g/m^3

Raise that air to 68F (saturation density = 17.54g/m^3)

2.01g/m^3
-------- = 11% RH
17.5g/m^3

...seems pretty dry to me. ;-)

That would indeed be pretty dry. Now, your next assignment is
to figure out why the air in my house *isn't* that dry! ;-)

 

[Rob Stow]

In Fairbanks the relative humidity can be very low. (However,
at the moment... it's 17F and RH is 91%!) But in Fairbanks
there is no source for water vapor /and/ it is commonly -40C or
colder. Fairbanks sits inland several hundreds of miles, right
between two of the largest mountain ranges in North America;
hence the relative humidity is commonly low, with no wind, and
in the winter there are extreme cold temperatures on a regular
basis. Static is a *big* problem when it gets cold, and only a
small problem with it isn't that cold.

In support of that ...

Where I live (Moose Jaw, SK, Canada) isn't 1000+ miles further
south than Fairbanks, but -30'C days are common during Dec,
Jan, and Feb, and most years we get a few days of -40'C weather.
100% or near %100 relative humidity on days like that is nothing
unusual - *outdoors*.

It takes trivial amounts of moisture in the air to cause near
100% RH at low temperatures like that. When it is -30'C and
100% RH, there is so little water in the air that if you heated
a volume of that air up to room temperature the RH would fall
to near zero.

However, except when guys like me do crazy overclocking experiments
outdoors on a cold day, the outdoor relative humidity is irrelevant.
It is the RH *indoors* that matters, and the colder it gets outside,
the harder it is to maintain a sufficient RH inside. Warm air is
constantly leaking out around doors and windows, up the chimney,
etc, and carrying away lots of water with it. If the water is not
replenished, such as by a humidifier mounted on the furnace, it is
very easy to have a 20% RH indoors even when the outdoor RH is close
to 100%.

Over the three coldest months of the year the humidifier for my
tiny 800 square foot apartment goes through about 6 liters of water
per day if I want to maintain a 40% RH. And that is over and
above the humidity replenished by things like cooking, bathing,
and simply breathing.

 

[Keith R. Williams]

That would indeed be pretty dry. Now, your next assignment is
to figure out why the air in my house *isn't* that dry! ;-)

You only heat your house to 32F (RH=44%)? ;-)

Seriously, your washing of circuit boards isn't as silly as people here
seem to think. The manufacturer washes flux off in what amounts to a
dish-washer. I don't think I'd want to leave a soap residue though.
Analogs certainly wouldn't like that much. A DI or distilled water
rinse would seem appropriate.

BTW, that's first-aid for electronics (and even cameras) after being
dropped in water. Take out the batteries immediately, then dunk in DI
or distilled water as soon as practical. ...cook on low heat until
done.

 

[Rob Stow]

BTW, that's first-aid for electronics (and even cameras) after being
dropped in water. Take out the batteries immediately, then dunk in DI
or distilled water as soon as practical. ...cook on low heat until
done.

Great for my little digital hearing aid too. At $65
per incident there is no way I'm going to take it to
the service center every time it gets a little sweat
in it and starts making everything sound like
exceptionally bad rap music. And at $2100 that hearing
aid costs a lot more than most desktop computers do.

In the summer, after rinsing things like that they dry
out quickly and safely if I lock them in the car for
an hour or so on a sunny day

 

[Robert Redelmeier]

And that *you* have little to no exposure to Arctic conditions

An incorrect assumption on your part. I've lived where -40'
was a normal temperature, and 0'F was a heatwave. Square
tires, double plug-ins, and driving with the windows open.
Ice-fog around open water. Now, I live someplace warmer.

It doesn't????

It does, particularly on the east side of the Rockies.

you claiming it is always high.

Always is a strong word I avoid using. It is possible to
get low RH cold air, but only by being colder first. Like
-80'F warming to -40'.

However, if you have *ever* experienced 6% relative humidity,
you know that static just crackles out of everything.
Yep!

You can't move without generating a charge. Everything you
touch gets zapped. You can't pet the cat, because it will
run when you so much as look at it.

And hair stands up at a distance.

Now, I'm not going to figure out what's wrong with
your calculations,

I doubt anything is wrong with the calcs, but the assumptions
might be mistaken. If you're running a humidifier (wet rug)
or have a tightly sealed house, of course the humidity is
going to be higher. As would [ice] fog.

I lived in Tucson AZ as a teenager. Trust me, in Phoenix
they have *lots* of static problems in the summer!

Thanks for the data.

-- Robert