On an Acer laptop running Debian 10.4, occasionally a few keys stop working. It is a few keys stopping to work for weeks, others for days or hours, or only for a few minutes.

The laptop is five years old and I tried to clean the keys underneath with an air duster but this doesn't help. It could be a mechanical problem in conjunction with corrosion, I assume. No key so far stopped working for ever.

The only thing, I don't understand is this:

Often, only capital letters don't work. That means, shift + r doesn't work ten times in a row, but r as minor letter works, all the time.

What also works, is caps lock + r, all the time, producing a capital R.

Why does work, the r key only, caps lock + r, too, but shift + r not? The shift key itself is working with all others key, instead. All the time.

Can someone explain please, why this should not be a software issue? I have no idea of what piece of software could be responsible for that, but it sounds rather strange to me.

All this behaviour seems to be independent form any application and I am using the command line program xev to test the keystrokes.

It sounds like a mechanical problem to me. Can you pry of the offending key caps (including the shift key) and clean out any dust or debris that might have accumulated?

If something has gotten under a key cap, it's entirely possible it might move around, accounting for the intermittent nature of the problem. Compressed air by itself might not be enough to dislodge it.

You might also boot to a Live CD/USB of some other distro and test (you would have to stay in live mode for a reasonable amount of time). If the problem does not appear, it might be a software issue, but, frankly, I've not heard of a software issue of this nature since I first started using computers in the DOS 3.2 days.

The above problem is still an ongoing issue.

I was wondering if someone had already issues with the keys similar to my problem or knows how such a keyboard is working. It is obviously an issue of that keyboard itself as the behaviour is the same when running Knoppix from a USB stick.

The issue that occurs temporarily is such that the "non-working" keys do work but simply need to be pressed longer. Up to a second or sometimes two seconds. The next thing is that upper case of those "non-working" keys doesn't work with the SHIFT key, but only with the CAPS LOCK key.

Another issue in the same way: the "<" key works in that sluggish way, but "SHIFT + <" doesn't give ">".

It probably doesn't help therefore to replace the "<" key? It needs to replace the whole keyboard?

Maybe more of a electrical versus mechanical problem. Basically the keyboard is a big switch matrix going into a IC that sends the key codes to the keyboard interface.

Replacing the keyboard assuming it contains all that on a single board should fix the issue. Although you need to determine if it is worth the cost.

You can use a USB keyboard as a workaround.

Run showkey from console - real console accessible via ctrl-alt-Fn, not a terminal. If it shows no keypress/release events it is 99.9% a hardware issue.

Check to make sure the keyboard ribbon cable is fitted securely to the motherboard.

1 members found this post helpful.

dilbert_uk,

As michaelk has suggested, first connect a functioning USB keyboard.
If that works perfectly, you need to replace the laptop’s keyboard. They are not generally expensive.

Examples of installation guide and keyboard:

https://www.ifixit.com/Guide/Acer+As...lacement/74925

https://www.ebay.co.uk/itm/Acer-Aspi....c101195.m1851

1 members found this post helpful.

While it probably is a hardware issue, it is not the way to diagnose it. In a 5 year old laptop keyboard is most probably connected to a i8042-compatible PIO controller which is completely independent from USB circuitry and drivers, so it will prove absolutely nothing.

The USB keyboard working properly would narrow the problem down to the built-in keyboard or the circuit path as far as they are different. The problems described seem to me to be limited to the keys or the ic chip within the keyboard itself. The keyboards I have looked at (including the one within my laptop) are usually a flexible sheet of plastic with the circuitry on it and the ic chip attached. The flexible plastic is backed by a rigid backplate.

While it is true that the paths between the physical keyboard and the usb keyboard differ in getting to the kernel, the most likely failure point remains the keyboard itself. The usb keyboard would confirm this is not a software issue but a mechanical one instead.
In fact, the intermittent nature of the failure and the fact that at times holding the key for longer makes it work is even more indicative of mechanical (likely contact) failure, possibly oxidation related.

1 members found this post helpful.

Is the problem with Shift+r independent of which Shift key you're using? If one Shift key works but not the other, that could be a workaround but muscle memory may make it a pain to get used to.

It's possible that the WAY you're pressing the Shift key depends on the letter you're "shifting" to uppercase. I'm thinking that the problem is an intermittent problem with the Shift key that depends on how it's being pressed. A minor change in the direction that it's being pressed associated with, say, the way your left hand is stretched to press both keys, is triggering the problem. I'm not sure how you'd fix a problem like that. Removing the key cover and checking for and removing any grit/lint/beer residue/whatever from the key/switch may fix it. The crud may be impeding the key from properly sliding and making the switch closure. You did mention that some "non-functioning" keys work if you hold the key down for a couple of seconds. Holding that key down may be overcoming the `debris/grunge problem'.

Some laptops make it fairly simple to replace keyboards. If more than one key is causing problems (as you mentioned above), it may be worth the effort to simply replace the keyboard altogether. Check with Acer on the availability of a replacement part.

Good luck...

1 members found this post helpful.

Yes, it's independent of which SHIFT-key, left or right, has been pressed.

I tried this already.

Thanks.