Hi guys,
New patient on the table. 
I got an old 1979 Apple II+ off eBay with a non-working 'O' key. This keyboard is the one with all the separate soldered individual keyswitches and integrated encoder board (it's not the separate one with the 25-pin cable).
I verified this was the only problem and disassembled. Tried to clean it with some "tuner cleaner" and that didn't help, so I checked with a meter and pushing the "O" key does short the contacts on the back of the keyboard, so the key "works". I put it back together again and notice now that the keys aren't "correct" anymore (and "O" still does nothing). Typing the letters works, but numbers and symbols are all wrong. Pressing 1 prints Q, 2 prints R, 3 prints S, etc. It's really strange. You can't even type the "return" key because it prints "M".
Anyone seen this problem before? The board looks clean- I don't see bad traces or cracks, but I can reflow the whole thing to see...
You have some dirty/malfunctioning keyswitches. Because of the matrix technique used to decode the keys, it will not be obvious which one(s) have issues. Check all of your key switches for problems with an ohm-meter. 99% Rubbing Alcohol seems to work better than tuner cleaner on these keys. Checkout my web page on the topic.
http://www.willegal.net/appleii/appleii-keyboard.htm
Be careful you don't zap the keyboard controller (40 pin chip) with static electricity, replacements are just about impossible to find.
Regards,
Mike Willegal
Thanks. I'll go over the board with a meter. While I was working on it last night, it started repeating the "@" symbol endlessly, then beeped, and then wouldn't take any keypresses. I fear that encoder chip may have failed.
None of the keys show any continuity unless they are pressed except CTRL and SHIFT. These show some, but not short by any means until they are pressed.
I think it is your encoder board. Those things are very static sensitive. Do you have a different one to try out? The keyboard is just a matrix of switches, that's it, all the logic is on the encoder board.
I had so many of these that had failed that I designed my own.
Vince
Unfortunately, not at the moment. I have a line on another broken keyboard so I may be able to merge the two.
You have a fix you've designed?
Yeah, I designed a replacement encoder board that also has a ps/2 connector for a 2nd keyboard. It's on my site. Given the nature of your keyboard condition, this isn't a mechanical switch failure, it's the encoder board. It may be good, and just the contacts need reseating, not sure. Check all that out.
Vince
Hi Vince,
Any way to get your encoder to work on a keyboard that had the encoder integrated?
Pete
Pete,
Sorry I've been away from fritter lately, busy. No, I only designed it to work with the keyboards with the encoder board.
Vince