Laptop key repeating - Toshiba C55-A5285

[goombawaho]

I've got a Toshiba C55-A5285 that starts repeating the ] key when it starts up. I found this out by running WSUS Offline Update and it gives you a notepad document with a summary of what updates were installed when booted up after the last updates. The notepad document started filling up with ]]]]]]]]]]]]]]]]]]] so there's your diagnosis.

Initially I pulled the keyboard off and reseated the little ribbon cable and that seemed to fix the problem. The key didn't repeat again for three weeks of periodic use. Then I sold it to a customer and it started happening again.

Question is this. Do I invest in a new keyboard or could it be the motherboard going bad? How to tell? I had to refund the customer so this is turning into an annoying and costly adventure.

"Living tomorrow is everyone's sorrow.
Modern man's daydreams have turned into nightmares.

 

[xwb]

Could it be something like a bit of chewing gum or crisps or something sticky under the ] key?

 

[rclarke250]

You could always pull off the key and inspect the dome under it. Carefully pry from the top of the key until it clicks off. Or the keyboard runs under $20.00 on fleabay, and just replace it. You can get replacement key assemblies and you could try just fixing the single key. they run about $8.00 a key from laptopkey.com. If it was me, I would just replace the keyboard, if it was the ,motherboard pulling off the keyboard, and hooking up a USB keyboard, would still produce the issue in notepad.

 

[goombawaho]

It's NOT the physical key that's sticking, no. No detritus in/under there.

Yeah, I was thinking about removing the keyboard and running with a USB keyboard and that SHOULD prove whether it's the motherboard or keyboard conclusively - correct?!?!

"Living tomorrow is everyone's sorrow.
Modern man's daydreams have turned into nightmares.

 

[rclarke250]

Well you won't be getting the signal return from the keyboard grid into the motherboard. so if the spurious signal is from the signal interpreter chip on the board it would still exhibit the issue. since it is more likely that it is a damaged trace or the carbon pad dislodged from the key dome and making a short, it should only show up when that keyboard is connected to the motherboard. And if the dome has become dislodged, you could take it apart and crazy clue it back inside the dome, if the dome is separate it is easy, if it part of a sheet, better to either get a key kit from laptopkey.com, and cut off the offending dome, as the kit will have a replacement, or just replace the whole keyboard.

 

[goombawaho]

I'm not fooling with individual keys - that's too tedious. So, I'll test the machine with no built-in keyboard.

"Living tomorrow is everyone's sorrow.
Modern man's daydreams have turned into nightmares.