Posting this here in the hopes that someone may be able to point me in the right direction for a fix.
Today I pulled my Obtronix out of storage. It was last used about 8 months ago and worked perfectly then.
It has a Briel Serial Interface installed, and the keyboard is from a Franklin Ace 1200.
The problem is that the keyboard is not working correctly. When I first powered on, only about half the keys worked. Over a period of about 20 mins as I tried to work out what the issue was, more keys seemed to stop working so now only about 1/3 of the keys work. It's strange that at one moment a key can be working (e.g. the return key) and moment later it stops working completely. I don't think it's an issue with the keys themselves (although I have yet to confirm that) as everything was working perfectly last time I powered it up, and has been working perfectly for about 7 years since I first built it.
I first thought it could be the keyboard encoder dying, except for another example of weirdness in that all the numbers on the main keyboard do not work, but about half of the numbers on the keypad still function fine, which makes me think it might not be the encoder after all....could be wrong.
I also contemplated the thought of some stuck bit(s) on the parallel keyboard buss, but quickly thought that if this was the case then I a key would still probably work, but produce an incorrect character on the screen.
I have also removed the Briel serial interface with no change.
Anyway, that's about where I'm at. Any thoughts or advice would be greatly appreciated.
I would first start with the keyboard and no power. Use a continuity checker and clips to check the contacts are good. They can be intermittent and cause a problem. If they are oxidized. Some Isopropyl alcohol can help if they are actual switches and not lead based like the later apple II plus keyboards. I'm not familiar with the franklin keyboard design. Also you will need to work the keys.
If you can get dexoit in japan, it works better than alcohol and usually if a key is just oxidized and not damaged you can revive the switch with repeated use when you use it.
Also the best way to work a switch is with needle nose pliers moving up and down not simply pressing the key.
I had a few spare mins this evening to pull out the keyboard. The problem is that Franklin Ace used those awful Keytronic foam and foil keyswitches. I pulled the back motherboard off, and indeed the foam was all deteriorated. I have the same keyswitches in my Apple Lisa and in my Sol-20, so I'm quite familiar with them. I have previously replaced the pads in the SOL-20, and I'm sure the Lisa keyboard will have to be done soon or later, but for now I need to find 72 foam pads for this keyboard. I though about making some, but it's a lot of effort.
All I can say is Mylar birthday balloons, clear acetate for overhead projectors, open foam weather stripping, spray glue and a leather punch...
Or you can buy a set for 60 on eBay. Not sure of the shipping charge.
I've bought and made my own. Obviously buying is easier. I made my own just to make sure in the future I have a supply.
I ordered these foam disks from ebay:
These are only the foam parts so I'll still have to recycle the plastic bottoms from the old ones, and make myself some mylar disks. Shouldn't be too difficult.