Many thanks to Jonathan Gevaryahu for his reply. Sean Riddle's https://seanriddle.com/kr3600.html is a wealth of information, including complete chip specs. Long ago, I did the opposite. I wired up an external keyboard to match the Apple ][ matrix and wired it up in parallel to the internal keyboard, rather than fix the broken keys. I worked briefly at General Instruments' Hicksville facility in 1982 so I have an affection for their chips. They were the heart of so many video games and speech synthesis. -- jeff jonas