# Unexplainable behaviour: PC doesn't react, keyboard and mouse lose power



## rf1002 (Oct 7, 2011)

Hi everyone,

I've been fixing computers in my spare time for almost 5 years now and I've seen some strange things! But this is by far the strangest thing ever.

I own a Fujitsu Siemens Scaleo P2 MS-7379. The processor is an Intel Core 2 Quad 6600 (2.4 Ghz) with 3gb ram (1x2gb/1x1gb).

A couple of months ago it suddenly froze. The keyboard and mouse lost power and I had to do a hard reboot. When it started happening more often, I tried
- reinstalling Windows XP, no result;
- installing Windows 7, no result;
- booting Fedora 15 from a Live USB, no result;
- replacing the CPU fan since the CPU temperature was sometimes very high;
- checked the CPU temperature after replacing, max 30/40 degrees celcius;
- checking the memory units (Memtest-86 says: pass complete, no errors).

After replacing the CPU fan, it worked for 2 weeks non stop. I was happy, very happy! But then, all of a sudden, while watching a high definition video on Youtube, the screen froze, the keyboard and mouse lost power, and the sound froze too (bebebebebebe, you know what I mean).

I have absolutely no clue what this could be! This extends my knowledge, I hope it does not extend yours - I hope you can help me because this has become very important to me because I want to find out what this is!

Thanks very much in advance!


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## bslevin (Mar 19, 2006)

Just an idea, since you stated that your CPU temperature was sometimes very high...

I had a system that kept freezing like that, sometimes it would reboot itself and sometimes it would freeze. After many months of trying everything possible and this only happening from time to time, i came across the solution..

Have you checked the thermal grease between the cpu and the heatsink? I tried this on a sugestion from someone and sure enough that was the problem. I added some new grease and the system has been running for 3 years since then without a problem.

Seems the cpu was overheating from time to time and would either freeze the system or reboot it.


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## JimE (Apr 16, 2009)

While anything is possible, I could see a heat issue causing lockups/reboots. However, the keyboard and mouse losing power indicate a motherboard issue. Whenever the PC is powered on (ie: motherboard has power), there should be power to the keyboard/mouse. Especially if one or both are USB.


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## rf1002 (Oct 7, 2011)

Thanks for replying bslevin and Dogg!
I was also thinking a motherboard issue because of the power failure.
I have cleaned the cpu, because there was a lot of thermal grease next to the cpu, but almost none where its supposed to be. I have out some new grease on the cpu and Ive tried to spread it evenly using a creditcard.
I've actually had it up and running for 6hrs now, I will keep on testing while a temperature logger is running from my usb-stick so I can check what happened after a shutdown. Thanks again, I will keep you posted and ask for help if it keeps failing!


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