Solved! HP ProBook 6555b overheating after switching mainboard

bugmenotplz

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Apr 13, 2014
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Recently my HP ProBook 6555b just turned of with a black screen. Due to the backlight still working, I thought, it might be a motherboard-failure. So I bought a cheap replacement-board from E-Bay and replaced it. And the ProBook started as normal.
But now, the CPU is getting overloaded very quick. Even so that it gets too hot and the ProBook shuts itself of. The fan is mostly silent, except if the CPU-usage is high for about one minute, when it goes to full maximum. The air coming out is warm and the fan has been cleaned from dust while replacing the mainboard. The thermal compound has been switched. The BIOS is up to date, even though msinfo32 shows BIOS-version F.60 10.11.2015 while the most recent version on the hp-website is F.60 Rev.A (30. Nov. 2015), but when running the installer it says, that it is the same version.
I don't know what to do now. It has been running cool with the dusty fan before the mainboard-replacement, but now its getting hot.
 

bugmenotplz

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Thanks for your help webworkings, but I finally figured it out.
It was the thermal paste causing the issues! After looking up the specs of the thermal paste used, I saw, it was only about 0.5W/mK, which is very bad for a thermal paste. I don't know, why I have such bad thermal paste, but it was the one laying around, and I thought it had normal heat dissipation. Well, I used new paste for the processor with 8.5W/mK and a Thermal pad with 6.0W/mK for the Northbridge-chip, which works perfectly fine!
 

bugmenotplz

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Well, it was the only motherboard I could find, and it was the right model and workes so far, apart from the overheating-problem. Also I couldn't find any new motherboards, as the notebook is pretty old now, but I still want to use it.
 

bugmenotplz

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I checked out the website, but the motherboard I need isn't avaliable. And even if it was, I wouldn't buy it, because the motherboard from ebay is working. I'm just not sure, if it's a software-problem, or the processor overheating due to bad heatpipe/thermal compound.
 
If the CPU is overheating, then you would likely need a new motherboard (most CPUs are not easily replaced) which would mean that it likely was a problem before you purchased it. This is why I suggested going through the manufacturer.
 

bugmenotplz

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Ok, but since that isn't an option, what can I do then, because I really want this notebook to keep working.
 

bugmenotplz

Honorable
Apr 13, 2014
32
0
10,590
1
Thanks for your help webworkings, but I finally figured it out.
It was the thermal paste causing the issues! After looking up the specs of the thermal paste used, I saw, it was only about 0.5W/mK, which is very bad for a thermal paste. I don't know, why I have such bad thermal paste, but it was the one laying around, and I thought it had normal heat dissipation. Well, I used new paste for the processor with 8.5W/mK and a Thermal pad with 6.0W/mK for the Northbridge-chip, which works perfectly fine!
 

hang-the-9

Titan
Moderator
Recently my HP ProBook 6555b just turned of with a black screen. Due to the backlight still working, I thought, it might be a motherboard-failure. So I bought a cheap replacement-board from E-Bay and replaced it. And the ProBook started as normal.
But now, the CPU is getting overloaded very quick. Even so that it gets too hot and the ProBook shuts itself of. The fan is mostly silent, except if the CPU-usage is high for about one minute, when it goes to full maximum. The air coming out is warm and the fan has been cleaned from dust while replacing the mainboard. The thermal compound has been switched. The BIOS is up to date, even though msinfo32 shows BIOS-version F.60 10.11.2015 while the most recent version on the hp-website is F.60 Rev.A (30. Nov. 2015), but when running the installer it says, that it is the same version.
I don't know what to do now. It has been running cool with the dusty fan before the mainboard-replacement, but now its getting hot.

Are you sure it's shutting off due to heat? If it was overheating the warm air would be actually hot, as would the system shell. Install HWMonitor, run that while using the system, see what the temps get to. Even if you put on new thermal compound, if the temps are getting to something like 90C for the CPU, you should check over the heatsink, maybe it's too loose on the CPU, or you used too much thermal paste.

CPU getting overloaded, that part I am not sure what you mean by that, do you mean it's running at 100% usage all the time?

Issue may be with the motherboard you got also if the fans and heatsink are on properly.
 
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