Ok, so almost three years hence, I am back at this project. I have sold or traded most of the boards (including one for known-good RAM chips - thanks
@Pushpull76 !). I desoldered that chip noted above and put in a socket. I sourced about twenty sockets, so I can theoretically replace them all. I still get nothing from the new chip, but I’m wondering if I a. Damaged all the RAM, or b. Have another issue with the board. Perhaps I should be scoping for signals, but I don’t know what to look for.