Great trouble shooting! You really spotted the problem there when the 74LS10 input was lifting the logic.
You have nothing to apologize for, it was not a well thought out design. It should never have been a 74LS10, but instead a 4023 as per the original ELF.
I'm guessing the designer of that circuit doesn't know from TTL/CMOS. How long has that design been posted for on Github? Can you have it corrected?
I wonder why no one else corrected it before you?
300 baud sounds slow, but it's still faster than I can think!
From: email@example.com <firstname.lastname@example.org> on behalf of John Kennedy <johntkennedy@...>
Sent: Friday, September 25, 2020 11:38 PM
To: email@example.com <firstname.lastname@example.org>
Subject: Re: [cosmacelf] Noob question: examine arbitrary memory address? #ELF #Memory
YES! Thanks all!
I swapped out the 47K for a 3K3, and look what happened.. Not only did the strobe start working but the serial port burst into life! (If 300 baud can burst anything).