Need help with 800XL keyboard

[DanBailiff]

Hey, my Dad sent me my childhood in a box, which included a 2600 (which I got working), a 400 computer with tape drive, and 800XL with floppy drive. The 800XL powers up and goes to the input screen, and I can get cartridges to work on it, and I even got my graphics tablet to work!

 

However, the 800XL's keyboard is not working on some keys. I believe it is a type 3 (non-mylar) keyboard. I tried just mashing the non-working keys repeatedly but to no avail. I opened up the whole thing for cleaning and while inside I followed the advice elsewhere of swapping the 4501 keyboard IC's to see if one of them was going bad. That produced no change, and about a third of the keys still refuse to work.

 

Is it possible the switches just need cleaning? Is it easy to pop off the keys and clean them somehow? Or will it require more effort that will involve soldering? I've done a little bit of that, but I wouldn't be super confident doing it myself.

 

Anything else I can try? Thanks!

[_The Doctor__]

de oxit is your best choice to go, If prying up keys make sure to do the straight up make your own pulling tool if needed, that way nothing cracks or breaks. Unless you see cold solder joints or the cable is oxiddised or damage you should be able to get it going again no problem, Just enough to clean the contacts. or a touch or two of a soldering iron.

[DanBailiff]

I just happen to have a can of deoxit I used to clean up a Mackie mixer. Thanks for the advice!

[_The Doctor__]

You dah bailiff? greetinx!

 

-D0C

 

Edited October 8, 2018 by _The Doctor__

[DanBailiff]

Well, I went the extra mile and took it apart so I could easily pop the keys. I used a can of Deoxit Fader F5 very generously on each key switch. It's probably not as strong as alcohol or regular strength Deoxit. I wasn't keeping close track but none of the non-working keys have improved at all. Even with a 2nd helping, the R key is unresponsive. I can see the switch making contact when pressed, so I don't know what the deal is. When examining the back of the keybed silicon, I didn't see any obvious signs of stress or cracks or severe oxidation. The ribbon cable is in fairly good shape but I could probably examine it a bit close for breaks. The contacts were clean and oxidation free which was kind of surprising. Maybe those switches are bad? Need re-soldering? I don't have a decent soldering iron and I'm not sure I'd have the practiced hands to redo anything. I don't know if it's worth trying to do more at this point. Are there replacement keyboards available?

 

On the plus side, the keys are no longer covered in the sweat residue of 13 year old me.

 

Thanks for the help, Doc!

Edited October 9, 2018 by DanBailiff

[_The Doctor__]

if you see no bad solder joints, and this is not a mylar keyboard as you said in the first post, then your next choice is pokey, check his socket for weak or broken swipes no bad solder joints on him and re seat him making sure no legs are missed on him or his support chips...

 

check keyboard connectors as well.

 

next step swap pokey

[JR>]

With this diagram, you can use a continuity tester to determine if the keyboard is the problem.

 

[rockdoc2010]

I would check the connector at the motherboard as well as the resistors associated with the data lines from the keyboard.

 

Get the matrix as in last post and test continuity between the switch matrix