Shared Knowledge
“Solving Dell SpeedStep
250N Laptop Random Shut Downs”
16 May 2006
Updated 6 May 2007
Recently received a Dell Speedstep 250N laptop from a friend that was randomly shutting it self down after being powered on for only a few minutes. Having experienced similar with other laptops, I suspected that the system was shutting down because a thermal protection circuit was protecting the CPU from burn out.
To
solve this problem, I performed the following actions:
1.
Examined the hinge cover and determined it was not held in place by
screws but rather just snapped into place. Thus, I laid the LCD down flat and
used a flat blade screwdriver to pry up on the hinge cover right where it
covers the right LCD hinge. Sure enough, the plastic hinge cover popped up and
then I did the same thing at the left hinge cover and it also popped up from
the back. (In retrospect, I think that if you laid the LCD down flat and simply
squeezed the hinge cover right where it covers the hinge using between 2
fingers, the hinge should pop up). The hinge cover has tabs on the palm rest
side that fits into the laptop case and thus once free on the back, I simply
lifted the cover forward and out of the way. Also note that the power button is
actually on the hinge cover and attached to the motherboard by a cable, so do
not yank the cover, just lift up out of the way.
2. Now I unscrewed the 3 screws holding the keyboard in place. The keyboard also has metal tabs on it, which fit into the palm rest end of the laptop case and thus to move the keyboard I lifted up on the rear of the keyboard and pulled it towards the LCD. As with the hinge cover, the keyboard has a cable running from it to the motherboard. Again, there is no reason to unhook this cable, just lay the keyboard out of the way of the fan, which is now visible on the right side of the laptop case.
3.
Examining how the fan is attached to the motherboard, I noticed a small
metal strip at the back of the laptop, which had to be removed before the CPU
fan could be removed. There is only one screw holding this strip in place but
note how it has tabs, which fit over and under metal of the laptop frame.
4.
With the small metal strip out of the way, I unscrewed the 4 screws
holding the CPU fan in place. Note that I unscrewed the 4 screws in a round
robin fashion as defined on the fan itself. 1, 2, 3 and 4. The idea here is to
relieve pressure on the CPU chip softly and evenly much like when you untighten
the lug nuts on a tire wheel.
5.
With all screws out of the CPU fan, I lifted it gently off the CPU and
laid it out on top the laptop with the heat sink side up. Sure enough, like
many other laptop manufacturers, Dell used some cheap and dirty thermal
transfer strip where the fan actually interfaces with the CPU. I now proceeded
to scrape off all the crappy thermal strip material from the CPU fan and then
cleaned it thoroughly so no sticky residue remained.
6.
I now covered the area on the CPU fan where it meets the CPU with
thermal conductive paste, which I bought at my local Radio Shack. Here, I am
not sure too much is too much. I did make sure the paste was evenly spread
across the fan heat sink area on the fan.
7.
I now reseated the fan on the CPU and screwed it in place in the same
round robin fashion, slowly tightening the screws a little at a time.
8.
With the fan now on the CPU, I reattached the small metal strip on the
back of the laptop frame, attached the keyboard and screwed it down and then
placed the hinge cover back into place.
Since I corrected the thermal interface between the CPU fan and the CPU, the system has been powered on and running a CPU stress test for 48 hours without a single random shut down.