A500 keyboard 2 keys not working

[Zippy Zapp]

Hi All,

Hoping someone can direct me to a tutorial or step by step on how or if it is possible to repair A500 keyboard.

I bought an Amiga 500 recently from ebay only to find out that the left shift key does not work nor does the 0 (zero) key on the numeric keypad. I read a few threads here about fixing the membrane but none of the threads had any how to do it or what is needed.

Is it possible to fix the connections behind the keyboard and what is involved with doing it?

If anyone has any suggestions or links that show how, that would be excellent.

Thank You!

[roy bates]

the keyboard might not be broken and the membrane might be fine,it just might be a case of taking the keyboard apart (lots of screws) and cleaning the membrane with a damp cloth.(use water not alcohol)
you dont have to remove the keys to clean the membrane,after the screws have been removed on the back metal plate the whole top half of the keyboard just comes off,give it a wipe and put it back together.
its just time consuming.

just be carefull though you can rub the carbon of the tracks if your heavy handed.

im suggesting this because if there was something amiss with the traces on the membrane you would more than likely find the other shift key wouldnt work and a row of keys on the numpad would be bad.as its a matrix.

best of luck.

[Zippy Zapp]

Ok cool. so it is not as bad as I thought. I will take it apart. I do see the little screws, wow there are a lot of them! This should be fun. Do I need to take the, what looks to be the controller, off and unplug that too?

Thanks,
-Paul

[roy bates]

no,you can actually leave that on as the controller connects to the membrane.
but,if you want to remove the controller while you clean the membrane you have to push back the clip and pull it off or pull out the membrane depending on how you disasembled the keyboard.
but i tried to explain it as simply as i could in text,if you just remove all the screws that holds the black plastic part on, it will come away and youll see the membrane underneath.you actually leave the controller onboard if you take note of which screws hold it on thats not holding the black part on if you see what i mean.
(you dont actually need to remove the controller to clean the membrane)

[Zippy Zapp]

Ok Got it. Thanks for the info roy.

-Paul

[roy bates]

i forgot to mention,some of the screws(the ones that hold the controller board in place are a little bit longer than the ones that just go through the metal to the black part,so keep them seperate if you remove them or the controller might not be held in place properly if you get the screws mixed up.

[Zippy Zapp]

Ok thanks for the tip. Will attempt this later today.

Regards,
Paul

[Zippy Zapp]

Well no luck on this one.

Took it apart and gently cleaned the membrane, still no left shift and num pad 0. Bummer.

Any other thoughts?

Thanks for the tips.

[roy bates]

yes,if you have a multimeter.

try to see if the contacts on the membrane give a reading on the connector on the controller,you can do this by removing the membrane completely put one probe on the one of the contacts for the key in question and trace it back through the membrane if it passes through another pad check it there on the way to the connector end see if you get a reading if so keep going till you get to the connector and test it there if you have a reading go to the other side of the pad and repeat the process.
do this with the membrane on its own without the controller connected.

when you done there,check to see if the plungers for those keys are giving a reading.put a probe on either side of the plunger base on the carbon part.

when your done with that and all is well,then try all the connectors that reprisent those keys on the controller.look for bad solder joints around the connector and around the large chip on the board.and look for corrosion or dirt in the connector housing inside the clip as well.

do the testing with the multimeter set to continuity test,it might not buzz but youll get a low reading around 200 ohm or lower i think, if you get nothing youll know theres something wrong and where it is.

either one of those tests will determin if you need a membrane a plunger or controller needs repairing/replacing.
oh,youve probably realised this is going to take a long time so make yourself a cuppa and good luck.


its a shame your so far away,otherwise i would fix it for you.

[Zippy Zapp]

Hate to bring up an old thread, but I have been out of Amiga fun for a while and I finally went back to fixing this and I figured out the problem.

I found a place online that had new A500 membranes in stock, US keyboard even. I bought one and they sent it to me this week. I just installed it and thought finally a fully working keyboard. To my surprise the same 2 keys didn't work! Left Shift and 0 on the number pad.

So I thought, after I re-read the message above, thank you by the way, instead of getting out the voltmeter I decided to swap one of the, I don't know what you call it, its the little plastic white piece that actually makes contact with the membrane. I swapped the 0 and 1 key on the keyboard underside and now the 0 works and the 1 does not. So it is that little plastic deal with the rubber tip!

Is there any way to repair those? They look perfectly fine. Can they be swapped from some other PC keyboard or something?

Thanks for all the help on this.

[Solo761]

Have you tried cleaning rubber part of non working plastic stub (in lack of better term). That rubber should be conductive, so if there's something stuck to it it won't make the contact. Q-tips and alcohol is what I usually use for this. If that doesn't work you could try silver conductive paint and paint over rubber legs that do the touching, that would ensure conductivity. Another quick fix would be to use standard pencil and "write" on contact part of the rubber. Graphite is also conductive so that would ensure contact. Although I'd prefer conductive paint, graphite could get smeared easily so in few months it could again stop working, or even make shorts so this key could register pressed even if it isn't. Altough in that case it could be easily fixed by just wiping the graphite from the membrane.

[Jope]

Clean the rubber contact with rubbing alcohol, then wipe the rubber against a piece of ordinary printer paper until it is no longer shiny. Then reassemble your keyboard.

Don't add anything (such as silver paint, graphite) to the rubber, just burnish it into a matte finish again. Good as new, will last another 10 years before it's time to roughen it up again.

[Vot]

+1 jope for the use of burnish in context.

I bet you have been waiting 10 years to use that baby in a sentence.

[kipper2k]

scrape the lead out of a pencil (it's carbon) and then tap the rubber pad from the key into the lead shavings, you want a light dusting. This hopefully should deposit a light layer on the membrane and fix it

[Vot]

Originally Posted by kipper2k

scrape the lead out of a pencil (it's carbon) and then tap the rubber pad from the key into the lead shavings, you want a light dusting. This hopefully should deposit a light layer on the membrane and fix it

Yep its graphite which is mostly carbon and a good conductor of electricity. Its also sold as a powder as a lubricant for locks.. But a pencil is certainly cheaper. So many people use a "wet" lubricant like oil etc on their car locks etc which is the worst thing possible, just ends up collecting dirt and jamming up the lock.

[Zippy Zapp]

Nice suggestions, thanks all! The membrane is brand new, so i am confident it is not that. I'll give these a try and report back.

[kipper2k]

Originally Posted by Zippy Zapp

Nice suggestions, thanks all! The membrane is brand new, so i am confident it is not that. I'll give these a try and report back.

when you say brand new... do you mean just manufactured, or new in your possession ?

[Zippy Zapp]

Originally Posted by kipper2k

when you say brand new... do you mean just manufactured, or new in your possession ?

Good point, I should have been clearer in my description of New. I think they were New Old Stock. But it was clearly new and not used. It was a waste, though as the old membrane was apparently working fine since the same two keys still don't work. I did clean the rubber part with iso last year but I didn't notice if it needed to be dulled or not to re-conduct it, if that is a term.

[Jope]

Graphite just makes a mess of things + half of it will stick to the membrane, causing potential problems. Cleanliness is key here. No dust and some nice dull rubber pads are the recipe for success. ;-)

[Jope]

Originally Posted by Vot

+1 jope for the use of burnish in context.

I bet you have been waiting 10 years to use that baby in a sentence.

Hehe.. It just popped into my mind as I was typing that.. Actually come to think of it, it was not really the right word to use here, as it's more of an act of polishing than dullifying. (is dullifying even a word? ;-)