Down arrow key not working on my Atmos

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protek
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Down arrow key not working on my Atmos

Post by protek »

I booted my Atmos after some time and I noticed that the down arrow key had stopped working. It doesn't 'beep' like the other keys and the cursor does not move down. It was working last time I tried it. Other keys seem to work, including the ones on the same column with the down arrow. Has the switch kicked the bucket?

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Chema
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Re: Down arrow key not working on my Atmos

Post by Chema »

You may try to remove the cap and clean the contacts. Most of the times that solves the issue.

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xahmol
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Re: Down arrow key not working on my Atmos

Post by xahmol »

What is next after trying to clean it?

On my latest Atmos (my second one) originally the 1, arrow down and space keys did not work. Cleaning contacts did indeed a lot, as all keys are working again and the arrow down and space even work well.
However, the 1 key has to be pressed really well for it to register. It is workable, but if it can be fixed further that would be nice.
Especially as this second Atmos actually does work perfectly with the Twilighte board while my first one does only unstable at the best, so if I can not fix that one I even consider swapping the keyboards. Any risk / thinks to be careful of there?

I actually tried unscrewing the whole board, but is it correct that the contact board is glued to the underlying PCB? And if correct, why are the screws there in the first place?
IMG_0398.jpg
IMG_0419.jpg
Also funny that it uses a completely different mechanism than a Commodore 64 keyboard, where you can actually seperate all the diiferent contacts one for one:
IMG_0248.jpg
Not even speaking of what goes for a keyboard contact board (or membrame actually) in the Spectrum (128 Toastrack in my case]

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Re: Down arrow key not working on my Atmos

Post by Dbug »

On the video of this guy, you can see how the whole thing is assembled, with the "sliding boxes" in the squares:

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protek
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Re: Down arrow key not working on my Atmos

Post by protek »

I did remove the cap and soaked it with contact cleaner. That didn’t help, unfortunately. Have to take a closer look at the switch.

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Re: Down arrow key not working on my Atmos

Post by protek »

I also checked the stem. I believe it’s all right as the jaws are making contact when I push the stem down.

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Re: Down arrow key not working on my Atmos

Post by xahmol »

Dbug wrote:
Fri Mar 05, 2021 5:07 pm
On the video of this guy, you can see how the whole thing is assembled, with the "sliding boxes" in the squares
Thanks and interesting. Learned that my Oric and my TI-99/4a actually use the same keyboard mechanism with interchangeable plungers.

Only the problem he is repairing here alas is different than I have. My key is not stuck. It pushes up and down well. It just only makes contact if you push really down. So it seems to me not to be the plunger, but either the spring or the contacts. The spring would be easy, the contact if contact cleaner did not help not so.
And also apparently the only way to repair a plunger is to take one from another retro board. That is a pity as well. Because now that scares me to pull a plunger out to see what I can do with contact or spring as I am afraid I will crack it.....
Maybe have to scavenge eBay then for a spare board. As I would hate to buy a working machine just to pull a keyboard out.

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protek
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Re: Down arrow key not working on my Atmos

Post by protek »

Apparently, you can print the stem.

https://github.com/AkBKukU/series80-ti9 ... eplacement

For me, that isn’t the solution. I need to open up my Atmos and see how it looks like on the other side.

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Re: Down arrow key not working on my Atmos

Post by xahmol »

protek wrote:
Fri Mar 05, 2021 9:11 pm
Apparently, you can print the stem.
Well, according to the video above that onky works with a very high quality printer and lots of patience as measurements need to be very precise or the key gets stuck.

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protek
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Re: Down arrow key not working on my Atmos

Post by protek »

Crisis averted! Turns out it was a bad solder joint in the down arrow key. A dab of fresh solder and it's working again!
Xahmol, if you haven't done so already, check and possibly freshen up the solder joints of the button that's giving you grief.

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Re: Down arrow key not working on my Atmos

Post by xahmol »

protek wrote:
Sat Mar 06, 2021 8:13 am
Crisis averted! Turns out it was a bad solder joint in the down arrow key. A dab of fresh solder and it's working again!
Xahmol, if you haven't done so already, check and possibly freshen up the solder joints of the button that's giving you grief.
Thanks. Will check. And just to confirm, is that the solder on the bottom of the keyboard PCB (so the other side that the keys are?)
Also I am not very confident with soldering still, so a little afraid I might actually do more harm than good.

Did this by accident on my very first soldering attempt desoldering the back of the caps lock key of a C64 keyboard couple of weeks ago, no harm but cosmetics, just ugly (but inside so nobody sees it), but does not boost confidence:
336E8056-A5F2-4C7F-B108-9D957C3509C9.jpeg
(On a C64 keyboard you have to desolder the caps lock key to get the PCB off to clean the contacts)

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Re: Down arrow key not working on my Atmos

Post by protek »

It’s the bottom side of the PCB. And the broken joint might not even be visible to the naked eye. Mine was just barely and I might’ve overlooked it if I hadn’t been specifically looking for a broken solder joint.

Keep your iron at 300 degrees, if it is adjustable and don’t hold the tip at one place longer than a few seconds and you should be fine. Flux always helps the solder flow.

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Re: Down arrow key not working on my Atmos

Post by Steve M »

You have to be careful soldering the keyboard contacts as they can move and become misaligned.
I use a continuity tester on a multimeter. (It beeps when you have a circuit.)
You can test the contacts beep when the key is pressed. Then trace back the circuit and check the line is intact. Sometimes the circuit gets corroded.

If the key operation is working and the track is OK then you need to look at the connector. The cables can fracture. I've had a couple that came off completely. You can get odd solder joints wearing. If you check the keyboard digram (in the Advanced User Guide and Service manual) you'll see several keys are linked. Usually if it is a broken connection you'll find all the keys in a row affected. So if you have more than one key look for connection issues. If it's only one then it is more likely the contacts themselves (or the chip.)

If everything checks out then it may be the chip. I had a board where everything worked but for a couple of keys. All the circuit seemed OK. So I changed the chip and then it all worked.

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