So I found http://www.apple1notes.com/old_apple/Peripheral_Boards_files/Keyboard%20Note.pdf after giving up on a late model II+ keyboard I am just fed up with trying to repair.
There don't seem to be any instructions or any sort of guidance on how this was done. Looking for advice on sourcing parts and getting a PCB manufactured. I think I am good with the electronics but any information on how the ASCII keystrokes actually work is welcome. I've never attempted anything like this from scratch before so any advice is appreciated.
Man - I must have a really bad memory these days. The last post I commented on was relevant to exactly this.
http://www.applefritter.com/content/diy-ascii-keyboard-apple-1-clones
I'll see myself out.