Playing Detective

This Fujitsu P7010 was purchased in 2004. After hundreds of hours of use and abuse, after bring hauled thousands of miles for car GPS navigation across Europe, after bring dropped on a tiled floor at least once, the internal cooling fan in the P7010 began to make noise. Consequently, in the fall of 2007, I opened the p7010 up, removed, cleaned, and relubricated the moving wear parts of the fan. And thought I was successful until this Spring of 2008 when the weather started heating up and BSOD (acronym for Windows Blue Screen of Death referring to the Windows white text over a blue screen diagnostic message) crashes started to occur.

Many things can cause a BSOD, so the first thing to be done is diagnosis. In general BSODs can be caused by software (mostly hardware-specific drivers like a driver for a specific printer or scanner) or hardware. So a good first step in understanding and fixing a BSOD problem is de terming whether the problem is software or hardware specific. By default, Windows XP attempts to be helpful by storing technical diagnostic information reflecting the state of the machine at the time of crash in the form of 64KB "small memory dump" files ending with the .dmp extension in the C:\WINDOWS\Minidump directory. With the help of microsoft's windows debug tools, we can see if there is any consistency, e.g., if the BSOD occurs within a very tight address range, a software driver problems moves up the suspect list.

P7010 Notebook Cooled by Window AC "Fixes" Problem

When the notebook is cooled by a window AC unit, it runs reliably overnight (8+ hours). Normally, a BSOD occurs within the first 2 hours. So it's a heat problem!

Determining Source of Overheating

(1) I lift up keyboard to take a quick peak at the motherboard to see if anything is obviously wrong.

(2) Indeed, I do observe there is a slight gap between the heatsink plate and the thermal pad. This gap probably is the culprit for the overheating. There is not supposed to be any visual gap between the thermal pad and the heatsink.

I will learn later after removing the heatsink plate that the device being cooled underneath the heatsink plate is the northbridge chip from the centrino chipset.

Baseline Temperature Measurement for Future Comparison

For future reference, I record the temperature after 10 minutes after power-on at a reference location. Of course, I hope to lower this reference temperature after I have corrected the gap between the TIM and the heatsink plate. Thus, the temperature to beat is 134F.

Damaged Thermal Pads

Review: Heat Removal from Electronic Device to Heatsink via Thermal Interface Material (TIM)

The two hottest parts are the processor and the northbridge chip. A heatsink plate extracts heat from the processor and northbridge. In turn, air passing over the heatsink plate (with the aid of a fan) extracts heat from the heatsink plate. As with standard heatsink design, a thermal interface material (TIM) acts as a very short heat bridge between the processor and heatsink plate.

From the factory, the P7010 uses thermal pads as the thermal interface material. If the heatsink plate is ever separated from the processor, they are to be replaced. When I looked at the heatsink plate after removing the keyboard, I could see a very small air gap between the heatsink plate and the northbridge. It turns out that I had reused the the thermal pads when I lifted the heatsink plate to lubricate the fan that became noisy!