Sammo said:
In terms of static, how safe is it to clean inside a home PC by using
a vacuum cleaner?
Some people like this website suggest that it is unwise.
http://www.dansdata.com/sbs3.htm
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.
If my PC is switched off but remains earthed (to the mains earth) and
I am careful not to do physical damage to the PC with my home vacuum
cleaner, then surely there is no problem with static?
Am I overlooking something?
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.
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.
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.
