Laptopsy, April 10, 2006

    Laptop computer autopsy: a laptop has developed a strange problem.  The machine is a Gateway laptop with an AMD 3000+ (1800 MHz) Mobile Athlon 64 processor.  When the machine is plugged into the AC adapter the machine will boot up and run normally, for awhile.  Then, usually when the cpu is under load, the fans will spin up and the machine shuts down without warning.  It will then start up again normally without a problem.  It will even run ok, if unplugged and running on battery.
    Web research says to clean out accumulated dust because the cooling air passages are clogged. The theory is the cpu is heats up abnormally and temperature sensors then save the cpu by shutting it down.  I tried blowing the ports out with compressed air and very little dust escaped.  So this was not a likely scenario.  Also some hint that the cpu to cpu cooler interface needs to be reseated with fresh thermal transfer compound.  The theory is that high temperatures dried out the thermal transfer compound and some kind of separation has occurred.  Or that thermal cycling has somehow squeezed the compound out.  I thought this sounded possible and was not afraid to dig into the machine.  Here are the photos of the machine disassembled.  Read the results at the bottom of the page.

Bottom view of the laptop, I removed the two necessary screws and set them near the holes they came from.  Note the thread locking compound on the tips of the threaded portion, this helps the screws stay in by being sticky.  It is red and sometimes blue.

This model of laptop is famous for it's spontaneously cracking hinge.  I mean famous, it seems to be a well known, well documented and unsolved problem.  Of course I didn't find out about it until after I purchased this laptop.  Take a look at this left side hinge crack, it looks bad.  But remember that the photo shows disassembled parts.  The laptop seems to function with the crack.  The screen will open, close and stay in position after you move it.  So we live with it, or should I say we baby it.

With the two screws removed form the back this plastic piece can be pried off.  I worked from left to right and back to front.  There are latching points behind the screen on the hinge covers and one in the back edge nearer the right side.  This part is connected by wires so you just place it to the side and expose the two keyboard retention screws.

Here is another view of the front plastic piece removed, you can see more clearly the latching points.

Ok, I breathe again and continue.  After the two screws holding the keyboard are removed and you slide the keyboard out of the way, you see a sheet metal cover with four screws holding it in.  Two screws are long and two are very short.  This photo shows the back side of the keyboard because it is flipped forward.  The sheet metal cover with four screws (two long and two short) removed are not shown.

Detail view showing the two through holes coming from the back and the two tapped holes in the back side of the fascia..

Detail views of the cpu cooler and the four screws holding it down.  The lower right screw has a very small screw and wire attached to the head of the screw.  There is another wire running across the cpu cooler/heat exchanger and it is held down with a stiff piece of transparent orange tape, Kapton.  You can also see the internal memory module in the lower left. There are two memory modules, SODIMM, one internal and one that can be accessed from the bottom of the laptop.

The cpu cooler is removed and you can see the thermal pad that has been crushed and smashed.  This is normal and thermally connects the two metal surfaces so that heat can travel easily from one rough surface to another.

This is what the cpu looks like.  I cleaned both surfaces with alcohol till they were shiny and clean.

I placed one drop of new thermal compound onto the cpu and replaced the cpu cooler and replaced all the components and screws.  Here is a photo of all the screws removed and the tube of thermal transfer compound from Radio Shack.  You can see how small the fasteners are.  The two long ones at the top are from the rear and hold the front plastic fascia piece that include the volume and power switch.  The two small screws at the top held the keyboard.  The two long screws and two small screws at the bottom held the sheet metal cover under the keyboard.  You can see the corner of the sheet metal cover at the bottom of this photo.  The tiny screw on the right was holding the grounding wire that was attached to the top of one of the cpu cooler mounting screws.  Four of which you can see are large, shiny and have a spring under the head.  The spring is supposed to push down and squeeze the interface between the cpu and cooler.

    Well after all that the computer behaves the same.  This fixed nothing, except my curiosity about the internals of the laptop.  I will have to investigate software solutions since the hardware does not seem to be an obvious problem.  Oh well, the thermal compound was less than two dollars, so no big investment so far.  But the saga will have to continue.