Keyboard issue - maybe controller?

Hello,

This is my first post, I hope it goes well.

The other day, I repaired a laptop for a friend of mine.  It is an HP Pavilion zv6015us.  When he brought it to me, pressing the key 5 on the keyboard would cause the machine to do very strange things, sometimes crashing the computer.  To test it out, I would open notepad (windows XP), and press 5.  Several characters would show up, including the time stamp (to get time stamp in notepad, press F5).  Half the time the computer would lock up.  So, I plugged in a USB keyboard, and the 5 key on the keyboard worked without problem.  I ordered a new keyboard from my distributor, and installed it.  To verify the keyboard, I pressed every key on the keyboard and it worked fine.  This was two weeks ago.

Earlier today he brought it back with the origional issue; the 5 key was causing problems.  Sure enough, the problem still exists.  I know it is possible to have received a bad keyboard, but what are the chances of both keyboards showing the same problems?  I have a feeling the problem may be with the motherboard, but I cannot prove it.

About me:  I work at a computer repair store for over two years.  I have replaced many broken machines ranging from MS-DOS to Vista.  I know much more about hardware repair than software repair.  Studing A+ and CCNA
KramdorAsked:
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rindiCommented:
This is very unlikely a controller problem. Much more likely is that there's a connection issue. As the controller is on the mainboard and affects both the internal and the external keyboard, you'd have the same issue on the external keyboard if it were a controller error. Check the internal cabling and the connectors.
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Rob HutchinsonDesktop SupportCommented:
Maybe this person plays games on their laptop, and the "5" key is programmed to launch grenades so just tell him to stop spamming grenades....

Seriously though, maybe he using the laptop for some application that requires him to press the "5" key many times...or the motherboard keyboard controller is bad.

What is strange though is that a replacement keyboard fixed the issue...although for a short period of time.
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KramdorAuthor Commented:
Thanks for the response.
A few minutes ago, I plugged in a known good USB keyboard, and the error only exists with the laptop keyboard.  What can I do (othe than replace the motherboard) to test the motherboard keyboard controller?

The user is an older gentleman who uses his laptop to do basic things.  I don't see him using the 5 key more than any other key.
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asiduCommented:
You could try disconnecting the keyboard and connecting it back again. As suggested have a look at the keyboard cables for any hairline cracks.  A replacement of the keyboard may solve the problem.
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KramdorAuthor Commented:
The cable is brand new and secured in its slot; the keyboard and all had been replaced with a new one and had been working.  There are no cracks in the keyboard cable.  Is it likely the keyboard connector on the motherboard for the onboard keyboard is faulty?
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KramdorAuthor Commented:
Update:
I found the old keyboard that I thought was faulty.  I have a friend who has a similar laptop, so I used the keyboard in that laptop, and everything works fine.  I believe I can reasonably say the motherboard is the cause of the problem.
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