Ethan Dicks wrote about the COSMAC Elf:
To guess, I know of one common issue with hand-made
1802 designs - the
4016 and 4066 are not 100% interchangable. They have different switch
response characteristics. ISTR the older designs used 4016 switches
which are harder to find now than 4066 switches.
It's certainly true that the
4016 and 4066 have differences in their
characteristics. However, in the simple way in which it is used in the
Elf, I can't see how it would make any difference. I can't say that
I've actually tried it, though.
If not that, then the other issue to investigate is to
ensure that the
input button is debounced
Yes, that is quite important.