Laptop ALT keys not working.

[kcs]

Hi all,

I have a client's laptop in at the moment, and I've got a problem with the machine that I can't really explain. The laptop is a Compaq CQ57 which has definitely seen better days.

Part of the job involved giving the machine an internal clean out and performing a bit of a repair to a broken headphone jack, which necessitated removal of the keyboard (among other things). Something sticky appears to have found its way under the keyboard at some stage in the machine's history, and when I've lifted up the keyboard I've damaged the ribbon cable, and a number of keys didn't work.

That's my fault, so I organised a replacement keyboard, and everything seemed to be okay. I ran a full check of every key, and both the Alt and Alt Gr (it's a UK kbd) don't register, but all the other keys work fine.

I've put in another new keyboard, with exactly the same result. I've ruled out the OS - the keys don't work in any environment, right from power-on (including the bios). An external USB keyboard tests fine. I don't definitively know whether the alt keys worked when I first got the machine (the client doesn't recall any problems with the keyboard, but I've no way to know whether that's truthful or even whether he uses the alt keys much).

In my time with the machine, I have had the motherboard out of the machine, so I guess it's possible I've damaged the board in some way (although obviously all appropriate precautions were taken), but I find it hard to believe that only these two keys would exhibit problems. I've also updated the BIOS, but with no change to the problem.

Can anyone please think of anything I'm missing here? I'm a bit stumped on this one.

Thanks,
Michael

 

[MichaelEC]

May be damage to the ribbon cable connector. I don't know what else it could be since you've already replaced the keyboard with the same results. Those ribbon cable connectors are so tiny too.

The only other thing I can think of is to see what keyboard is loaded in the keyboard options menu.

 

[GTP]

The only other thing I can think of is to see what keyboard is loaded in the keyboard options menu.

Just for giggles try loading different keyboards, like US, GB, Fr etc and test if the Alt keys work with them.
There are several different English keyboards as well- Belize, Canada, Ireland etc. Try them as well.
Failing that, the other answer seems most likely.

as @MichaelEC said, "May be damage to the ribbon cable connector"

 

[Calx]

I take it you have plugged in an external keyboard and that works fine?

 

[kcs]

Just for giggles try loading different keyboards, like US, GB, Fr etc and test if the Alt keys work with them.
There are several different English keyboards as well- Belize, Canada, Ireland etc. Try them as well.

Yep, same story - everything is fine except for the alt keys.

I take it you have plugged in an external keyboard and that works fine?

Yes, USB keyboards work fine.

May be damage to the ribbon cable connector. I don't know what else it could be since you've already replaced the keyboard with the same results. Those ribbon cable connectors are so tiny too.

Looking at the connector under magnification, it appears that all the pins are intact, although as you say, they're so tiny! The locking tab on the top of the connector doesn't seem to be broken - it's still holding the ribbon firmly when closed.

I'm not totally across how the keyboard interface works here, but I assume it uses a matrix of some sort, in which case it'd be unlikely that only the alt keys would be failing if a pin on the connector was faulty - it should be affecting more keys that that, shouldn't it?

 

[MichaelEC]

Yes, it should. When I was building my 727 simulator I had learned a lot about how the keyboard matrix was set up. I have since forgotten that over the years, but it is on the internet. It would affect more than just the Alt keys though.