Amiga 500 keyboard 5 keys not working

[Nikolaj_sofus]

I recently found an amiga 500 in the trash.
It works fine except for a couple of keys on the keyboard.
Are these problems normally fixable?
Its a vertical row of keys.
2, w, s, x and space, so i guess its a missing connection somewhere.
Anyone had this problem before and managed to fix i?

[Nikolaj_sofus]

any ideas?

[Jope]

Either there is a break in the contact membrane or your keyboard controller is shot.

[Nikolaj_sofus]

Originally Posted by Jope

Either there is a break in the contact membrane or your keyboard controller is shot.

and that can cause a partial fault?
i checked the membrane visually, but cant see anything wrong on it.
But it does fit that those keys are connected somehow.

What about the CIA's
Can they be faulty?
Is it possible to source a single keyboard controller?

[Abaddon]

My 1200 had a problem of a few keys not working. I removed the keyboard from the motherboard and cleaned the contacts, reconnected and everything was fine. Not sure if the a500 has the same membrane connector.

[Jope]

Originally Posted by Nikolaj_sofus

and that can cause a partial fault?
i checked the membrane visually, but cant see anything wrong on it.
But it does fit that those keys are connected somehow.

What about the CIA's
Can they be faulty?

Yes, but then you'd get no communication from the keyboard at all. The Amiga's keyboard is serial.

Is it possible to source a single keyboard controller?

I'm sure people have them floating around.

Originally Posted by Abaddon

My 1200 had a problem of a few keys not working. I removed the keyboard from the motherboard and cleaned the contacts, reconnected and everything was fine. Not sure if the a500 has the same membrane connector.

It does and the membrane pinout is actually the same too.

[Nikolaj_sofus]

Originally Posted by Jope

Yes, but then you'd get no communication from the keyboard at all. The Amiga's keyboard is serial.



I'm sure people have them floating around.



It does and the membrane pinout is actually the same too.

does that mean that i can actually try the keyboard from my a1200 on the connector?
there are no active components on the a1200 keyboard are there?

[Jope]

You can plug an a1200 keyboard into the small controller pcb that is found in the corner of a500 keyboards.

However there are two kinds of a500 controller boards. One connector and two. You want the single connector kind.

[Nikolaj_sofus]

Originally Posted by Jope

You can plug an a1200 keyboard into the small controller pcb that is found in the corner of a500 keyboards.

However there are two kinds of a500 controller boards. One connector and two. You want the single connector kind.

then its good that i got a single connector type

[orange]

I'd say its bad contact, or that line is broken. because, iirc, those keys lie on the same vertical line. so it should be an easy fix. hope you got liquid silver or graphite or similar and multimeter.

[pandy71]

Check KB matrix - best idea is to clean everything and verify that all traces are OK.

Dismount whole KB (make photo of key maps), then verify matrix, traces are made from thin metal - can be corroded after many years - such matrix can be repaired by conductive glue - quite easy to make, just use same tape to mask area around trace then apply conductive glue on traces - after time required to dry just remove masking tape and You have nice new trace.

something like this

http://192.197.62.35/staff/bgracey/p...ardrepair.html

[Nikolaj_sofus]

i'll try with the a1200 keyboard first, and if that works, i know that its a problem on the membrane.

[Nikolaj_sofus]

ok, it works fine with the a1200 keyboard, so it must be the membrane its wrong with.
I guess im gonna get my multimeter out and measure it trough

[Nikolaj_sofus]

Just bought a new/used membrane on ebay.... gonna see if that does it.

[avantgarden]

Sorry to teleport this to 2020... It's for adding it to the Knowledge base.

Identical issue here:

- Amiga 500 year 1991 REV 8A

- Mitsumi keyboard with single flat cable

- Broken keys: 2wsx

- Cleaning membrane didn't help

- Swapped keyboard with an Amiga 1200 one, ALL KEYS WORK NOW

- Problem is the membrane!

- Opening the orginal keyboard again and reporting back with photos!

Thank you.

[avantgarden]

Findings:

- For quick testing you don't have to reassemble the keyboard!

- You can just "lean" it over the membrane with ZERO screws attached! IT WILL WORK AND SAVE YOU A LOT OF TIME!

- It will also preserve the keyboard since all screws are self-tappers!

- Cleaned again with a damp cloth (demineralized water)

- 2wsx DON'T WORK...

- Don't have a multimeter so no continuity test...

- All seems in good shape to me!

Photos:

https://drive.google.com/drive/folde...RVeMqe8lTWtkDq

The close-ups shows the "2" key.

[solarmon]

@avantgarden

To help with troubleshoooting the keyboard membrane I have created some keyboard mappings at:

https://github.com/solarmon/Amiga-Keyboard

Specifically, for this keyboard membrane you can find the files at:

https://github.com/solarmon/Amiga-Ke...itsumi%20A619B

The trace for keys 2, W, S , X is the Y12 trace.

If you use the mapping files, you will find where the Y12 trace goes. You will find that the traces goes between the carbon pads of the Number Pad 1 key.

On your last picture of the whole membrane this key is just above the brown patch, and the Y12 trace goes through this brown patch, which I suspect is where the break in the Y12 trace is. Get a closeup of this brown patch area.

Edit: You should find that F1 is not working too. I would recommend using Amiga Tesk Kit to test the keyboard keys - it will give you a nice visual view of working and non-working keys.

[avantgarden]

@solarmon

Spot on! You remotely diagnosed my keyboard better than I did locally...

F1 key is not working as you predicted. So it's a "continuity" issue!

The Y12 track passes under a few "holes" in the keyboard where the nasty brown patch was (I've gently removed it without solvants).

More pics:

https://drive.google.com/drive/folde...RVeMqe8lTWtkDq

I'm afraid I will not be able to pull these stunts here:

[ Show youtube player ]

Your mappings are a must-have for technicians!

Is the Amiga 4000 keyboard membrane compatible with A500 one?

Best wishes,

AG

POST SCRIPTUM:

This software http://aminet.net/package/util/misc/KeyMapEd can also be used for a quick test!

[solarmon]

@avantgarden

Looking at the pictures you have provided, it is possible that the break is where that dark round spot is on the Y12 trace going between the pads. The reverse picture of this, you can still see this dark patch which could indicate a break.

Shine a bright light behind it and it may be more obvious.

Do the same for the Y12 contact on the flex connector - it could be that the carbon has been scraped off when the flex cable has been taken in and out of the connector. If there is any light shining through then that is a break and no contact.

I'm not sure about the A4000 external keyboard - but I don't think they use a membrane.

The broken tracks can be fixed with silver conductive ink. If you can't or do not want to fix it then I would recommend the replacement PCB, not membrane one:

https://www.sordan.ie/product/713/ne...0--1200-green/

(However, I have not used these yet).