Dave,
Thanks for the TRS-80 tear down! I really loved watching it.
You may want to pull off one of the keys from the keyboard. These switches were springs, and the hardware didn't have any debounce. There also wasn't any in the ROMs. Later there was additional software you could add that would do software debounce. However, I followed advice to use WD-40 on a sheet of paper and insert it between the springs in the key and depress and pull the paper through. This deposited enough goo on the springs to tame the bounce. And it did work, believe it or not.
Also, I would love to see the RF output if you put some work on that Z80. I bet it'd be significantly more noisy. A simple loop should be enough:
10 goto 10
--
Jeffrey Hundstad
Long time viewer, first time post. I couldn't resist.