Laptop keyboard problem - Ctrl & Alt not working

I have W25CSW laptop that is little used and in excellent condition.

Recently several keyboard keys have stopped working. “Ctrl” (both left and right) and “Alt” are hard fail. Backspace and “(“ are intermittent. The very odd thing is that when “(“ [shifted “9”] isn’t working the “9” remains working. “(“ and “9” are of course the same key.

I don’t think it’s a failure of the physical keys as it’s unlikely they would fail at the same time. The right “Ctrl” is never used so it won’t be worn out. I have reloaded system drivers.

I’ve used some of the online keyboard testers and they show the keys not working. Is there any way I can check the actual scan codes being generated (or not) by individual key-presses? That would help with fault diagnosis. I guess at some point I will have to check the keyboard connector for problems, but would like to have a ‘scan code checker’ first.

Any other suggestions welcome.

Because of the way the keyboard circuitry tracks and the controller operate it is possible that an issue exists in a track and because of this some keys have lost function as the correct combo cannot be pressed to generate the correct keyscan. Although this tends to happen in groups when its circuitry problem. If the keyboard has not been exposed to any liquids that might have caused problems in the membrane to detect key presses then only other thing would be to check that keyboard cable is properly and fully seated in to the motherboard connector. Otherwise it could be a fault in the controller itself. Does the shift key work with other keys ok???

Thanks for the super-fast response!

Shift key is fine – even with “(“ just now as I’m typing on the faulty laptop. It’s just the Ctrl and Alt that are stone dead. I’m pretty sure it’s not a membrane or actual key problem as the laptop is like new – no spills, etc. For various reasons it was not used for two or three years from new and I only started using it a few months ago.

As you say, I will have to check the keyboard connector. Is there a service manual or similar with disassembly instructions? I’m an experienced hardware tech.

Yep you can see ESM here

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Thanks for the link. The keyboard ribbon cable looks OK - no visible track breaks. Cleaned connector and cable end with contact cleaner. No joy. I assume there’s no point using contact cleaner on the individual keys as they are not mechanical.

Both Ctrl and both Alt keys still stone dead. Backspace and Del keys intermittent and getting worse, which make me think it may be a dry joint on the keyboard controller chip, or hairline crack on a MB track.

Before I open up the MB it would be good to eliminate the keyboard once and for all. What is the chance of you having an old keyboard kicking around that I could borrow? :slight_smile:

I have managed to locate one in our service department… no easy task but i have one luckily.
Drop me a mail directly at john.cooper@novatech.co.uk and we will sort out getting this out to you as a loan for testing.