My computer recently had a smell coming from it.  It was like a
chemical type smell or like that of burning plastic.  I am told it is
rather pungent.  What commonly causes problems like this, and how is
it fixed? It happened once before,  about two and a half months ago. 
But I haven't had the problem again till now.  The fan has lately been
working harder.  My computer is  a Pentium II with Windows 98, 1st ed.
 We bought it new sometime in 1999.

Dear rosemary25-ga;

Thank you for allowing me an opportunity to answer your interesting
question.

If you run your computer for long hours or make great demands that
your computer might only be minimally able to achieve, or if your
computer is older, it quite likely that the thermal conductive
compound on the bottom of your heat sink has dried and/or broken down.
When this happens the compound can scorch at high temperatures that it
may have been quite tolerant of previously.

If all this sounds like Mandarin Chinese to you, maybe this
explanation will clear things up for you:

Heat sinks are devices that help dissipate heat from a hot surface,
such as chips or co-processors in your computer. It basically lowers
the temperature by providing a larger surface area in which the heat
can be stored. That’s why heat sinks usually have lots of folds, walls
or ribs, much like an old room radiator (if you’re old enough to
remember those or happen to live in Europe where they are still
frequently used, you know what I am talking about). The more of these
ribs there are the more available surface area there is to store
generated heat.

The heat is transferred from whatever surface it is being generated
from, directly to the heat sink. Because there is ample space to store
the heat, there is also ample surface area to cool the heat down,
especially if a fan is added to the formula. The fan, in your computer
is used precisely for this purpose. Many fans blow into the case,
forcing cooler outside air across the ribs of the heat sink, and in
turn, forcing the hot air out though small openings in the back of the
case, thus reducing the temperature inside your computer.

Now, when your heat sink is installed, a thermal conductive compound
(sometimes inaccurately referred to as glue or adhesive) is normally
applied to the area of the heat sink and the co-processor to keep the
co-processor from heating up and scorching anything it may be in
direct contact with. Because this “grease” has thermal conductive
properties, it allows the heat to pass through without damaging (i.e.,
melting) anything – sort of like handling a hot cake pan with a
potholder. In this way the heat migrates from its source (the
co-processor) onto the nearest surface (the ribs of the heat sink) and
is then cooled by direct application of cool outside air (the fan) and
dissipated.

So, you see, when the thermal conductive compound breaks down, as it
sometimes does under intense heat (or after a certain age,
particularly if the original compound used was a cheap, off-brand) it
sometimes tends to scorch. If this is the case, the smell you are
noticing is probably the old grease on the heat sink that is
“cooking”. The reason you do not smell it all the time is because of
the temperature variations. You computer is much cooler at boot-up
than it is after having run for some time. If your computer reaches a
high temperature and sustains that level of heat for a long time, your
fan demands will also be greater.

If you do not know how to replace the grease and/or the heat sink
itself, (and you probably should for safety reasons if nothing else)
you might be able to contact a local repair shop and get some free
phone advice on how to do it. Additionally, you might contact your
local college or technical school and see if they can recommend a
student who does such things on the side and wants to make a few extra
bucks (most computer savvy kids can do this in only a few minutes).
The bonus with using the student option is that they will readily
answer any other questions you may have simply because they like the
topic and are usually willing to teach their tips and tricks to anyone
who will listen. Finally, if you adventurous, you can study this
repair on the Internet and try to do it yourself. If you choose this
method I recommend you print out any documents you plan to refer to
rather than replying on memory alone. I should also point out that if
you buy a new heat sink it would probably have some degree of
replacement instructions with it in the box.

Below you will find that I have carefully defined my search strategy
for you in the event that you need to search for more information. By
following the same type of searches that I did you may be able to
enhance the research I have provided even further. I hope you find
that that my research exceeds your expectations. If you have any
questions about my research please post a clarification request prior
to rating the answer. Otherwise, I welcome your rating and your final
comments and I look forward to working with you again in the near
future. Thank you for using Google Answers.

Best regards;
Tutuzdad-ga


INFORMATION SOURCES

HOW TO SELECT A HEAT SINK
http://www.psc-cp.com/Thermal_New.htm

THERMAL HEAT SINK COMPOUND
http://www.amdworld.co.uk/compound.htm




SEARCH STRATEGY


SEARCH ENGINE USED:

Google ://www.google.com


SEARCH TERMS USED:


THERMAL CONDUCTIVE COMPOUND

THERMAL GLUE HEAT SINK

HEAT SINK REPLACEMENT

COMPUTER HEATSINK

---

Request for Answer Clarification by rosemary25-ga on 24 Dec 2002 12:12 PST

Do you know what might constitute "great demands" on the computer? 
Having it on for a long time would or having too many programs
running.  Would playing arcade games as  my brother does be more
demanding than say, chatting online or doing searches on the Internet?
  Graphics probably put on more demands than simple word processing,
true?

---

Clarification of Answer by tutuzdad-ga on 24 Dec 2002 13:37 PST

Yes, you are in the right track. Generally speaking, "great demands"
would be any complex computations that exceed the routine capabilities
of your processor. These might include such things and gaming beyond
recommended processor thresholds, operation of many applications at
once, operation of graphic intense wares, or operating for long
periods of time. Aside from this, great demans might also be caused by
enviromental factors such as a dirty case interior that does not allow
for proper ventilation or external accessories that require more
memory that what you actually have onboard.

I hope this clarifies it for you.

Regards;
tutuzdad-ga

Thanks. All I needed to do was replace the computer's fan.  I haven't
noticed the burning smell since then.

Just to warn you, rosemary, that the fumes produced by burning
circuitboards can be HIGHLY toxic, so try and ventilate the area well
if this occurs again!

Regards,

--seizer-ga

I agree with seizer. The smell could be coming from your monitor as
well. Something is burning so it would be good if you get a technician
to check and clean your unit since it's an old system.

- Feilong

Dear Tutuzdad,

I hope you are a teacher.  In my book, you score an A+ in the art of
explaining AND writing.

JCG

I believe it is equally important to point out another possibility of
origin of a rather pungent smell. I have had several experiences where
the power supply in a computer has failed, or had begun to fail, in
which the circuitry components inside the power supply overheat,
producing the odor. The power supply is the usually-gray box that is
located in your computer case where the power cord plugs in to.

Since the smell of "burning electronics" is very potent, simply turn
off your computer and gently sniff (not too hard as to inhale any
dust) the fan grill on the back of your power supply, and if there is
a extremely unpleasant, pungent smell, then you may suspect that your
power supply may be starting to fail. Keep in mind that there will be
a mild odor, even on a perfectly working power supply. If you have
another computer that works, you can compare the smells, and if the
suspect computer has a significantly more mal-odorous smell to it,
then it may be a good idea to start pricing power supplies.

As mentioned before, another source, although not as notable as the
power supply, may be your monitor. If a lot of dust has collected in
the top ventilation holes on the monitor’s casing, then it just may be
heating up and producing an odor. Again, a warm monitor can generally
smell strange and/or unpleasant, but if a odor is noticeable while
sitting in front of your computer normally, and you sniff the top of
your monitor and the odor is so much more stronger that there is
significant reason to believe the monitor is the odor’s origin, then
the monitor may be the source.

As a safety notice, if you wish to clean the dust from the top of your
monitor, either use a vacuum or blow it out of the ventilation holes.
NEVER under any circumstance, whether unplugged or not, remove the
casing on your monitor, or any TV or device that contains a cathode
ray tube. The tube inside stores extremely high voltages that can
remain resident for a very long time, often for months on end.

-- paper