A4000 keyboard

[CrazyC]

Hi
I have an old a4000 keyboard where one or two of the keys are either requiring a few goes to work or not being registered at all. I figured I would replace the membrane and that would sort it hopefully. So I took it apart but it appears to be one solid hard part, no separate membrane?
Am i missing something or does anyone have any suggestions?
Looking at the PCB it says A2000 on it, but the outer case definitely has the ridges etc.
I dobt really care which it is, i would just like it fully functional. Its has the small ps/2 type connecter with a short cable adapter converting it to a din connector into the amiga.

 

[Xanxi]

I would take it completely apart to give it a thorough clean, as it shows seom dirt on the keycaps, i can only be worth inside.
Beware, no alcohol on the pads but slight friction with the so called paper trick.

 

[btp]

Big box Amigas keyboards instead of a membrane they use a PCB. It's more durable and easier to repair if needed. After cleaning as Xanxi rightly suggested I would also test continuity (with a multimeter) in the traces used by they keys that are not working.

 

[CrazyC]

I would take it completely apart to give it a thorough clean, as it shows seom dirt on the keycaps, i can only be worth inside.
Beware, no alcohol on the pads but slight friction with the so called paper trick.

The so-called paper trick?

 

[btp]

Run a few times the rubber pads of the problematic keys over a plain page of paper. It's abrasive enough to clean the pads without causing any damage.

 

[amigean]

I read online, several years ago, that writing over lightly with a pencil over the contacts can restore functionality. Apparently it is due to the pencil 'lead' (not real lead of course) being an electrical conductor. I tried that with some errant keys on my A3000 keyboard and it worked! Well sort of, they work for something like 8 out 10 presses, which is a lot better than not at all. They still work just as well all these years.

I have since wondered if there may be a better solution, some paint-like conductor like the original contacts perhaps? There appear to be a keyboard repair viscuous substance jar on sale in ebay and other places but I never felt I needed it enough to buy it. If anyone has tried it it'd be good to hear about it.

Hope you fix yours!

 

[CrazyC]

Silly question, is the lead applied to the contacts on the pcb, or on the back of the keys, or both?

 

[amigean]

It's been many years so memory could be playing trick on me, but I think I tried both on the PCB and behind the keys but only the PCB application made a difference.

In my case, by the time I read about applying the lead, I had already made the mistake of cleaning it with alcohol which is not advisable. So there could have been more of a need for a conductor-like substance in my keyboard, than in yours which may just need cleaning.