Atari 800XL Keyboard help PLEASE

[NAMSS Gamer]

Hey guys,

 

I just received an Atari 800XL from an eBay seller that was selling it as is. He said he had no power supply, so when I got the computer, I used my USB power supply for the computer to power it on successfully, although the keyboard is having some serious problems. Keyboard kept pressing one of the keys and it doesn't stop until I turn off the computer. Same thing happened when I cleaned and deoxidized the keyboard connector and when I cleaned the inside of my mylar board that was inside the keyboard. Then I began to realize that the keyboard mylar was black in some areas (picture shown here). So in essence, should I replace the keyboard or just the membrane? I think my keyboard is a Type 4 as someone else defined.

Edited October 21, 2022 by NAMSS Gamer
Want to bump this thread

[reifsnyderb]

Hello,

 

Is the black area a crack?  If it's cracked, the mylar will need replaced.

 

If not, I'd tear the keyboard apart and see if the mylar is stuck together on the stuck key.

 

Also, I've found that if the spring, for the key, sticks out too far that the mylar will be held together.

 

Also, if you take apart the keyboard make sure you take the metal plate off with the keys down on a table.  Otherwise, you'll have springs everywhere.

 

 

 

 

[NAMSS Gamer]

Well I don’t know if there is a crack, but the traces and pins are like black right at the end. Not supposed to be like that as far as I’m concerned.

[reifsnyderb]

If the keyboard traces were broken, you wouldn't have it acting like a key was held down.

[Beeblebrox]

Firstly can you confirm if it does it with only certain keys? 

 

If so what you could do is ease the little screws on the underside of the keyboard a little in that area. Sometimes they can be overtighted. 

 

It could be a combination of things tbh so as usual with these ol computers it's a process of elimination. 

 

Sometimes repeatedly pressing a key that is playing up eventually sees it sort a particular problem out. 

 

With these mylar based ones a load of problems could arise and yeah you may need to either clean it, fix it, (eg with conductive paint to restore any broken mylar tracks), etc. 

 

Another cause of some keyboard failings are that the 4051BE chips are failing. 

 

I'd go with the simple tests first - ie ascertaining whether only with a localised key or keys - where again easing off little screws is an easy thing to do in the first instance. 

 

BTW if you have non functioning keys in a line at any stage this is a telltale sign of a bad mylar track connection as they are connected in matrixes. So several can be knocked out at once. 

 

Do you have a multi meter with continuity functionality BTW? When fixing a mylar it will be essential. 

 

And yeah as per comment earlier if you do take off the backplate to get to the mylar make sure you have the keys face down at all times and don't flip it, or you'll be hunting for a ton of springs on the floor!! 

Edited October 21, 2022 by Beeblebrox

[NAMSS Gamer]

4 hours ago, Beeblebrox said:

Another cause of some keyboard failings are that the 4051BE chips are failing.

Is that the Pokey chip? And where do I find replacement 4051BE chips?

[NAMSS Gamer]

Well guys, great news. Got the keyboard situation fixed. What happened was the POKEY chip on my Atari 800XL was failing although the sound was fine. I replaced the original chip with a spare POKEY that I bought last year that I was using for my Concerto cartridge for my Atari 7800 and the keyboard is now operational, although the return key needs a lot of effort for the input to work. Glad I was able to get some help guys.

[_The Doctor__]

remember that pokey may still be good for stereo gumby use, those are still useful sometimes.

[Beeblebrox]

Yup - I second that.  Never throw a Pokey if failing. I've used a failing Pokey (where sound functionality still worked), as a second Pokey chip in a Simple stereo board and all worked fine.

 

Saw someone selling a single Pokey chip for £70 on ebay the other day!

 

Hopefully Pokeymax units will be returning soon.

 

Then all that is needed is a modern equivilant of the ANTIC chip!