I got my F77 working.
@Twst, thanks for the confirmation about the keys needing to be present. That got me 90% there. I had already tried the Q-Tip trick to remove the stabilizer, but the stabilizer was way too tight for that to work. I tried stuffing two Q-Tips in, as shown in the video, and that wasn't even close to enough grip. Now that the barrel is out of the keyboard, I could probably push the stabilizer out with a vise and a pin punch, but instead I think I'll just stash this barrel in my spare parts kit as is, in case I ever work on a keyboard that needs a vertical stabilizer barrel. (I bought the first-aid kit so I have some spare barrels and stabilizers.)
@E3E, I don't need a flipper there, where the stabilizer was. I was working on installing the Enter key (ANSI, horizontal bar). My keyboard came without keys, and I was installing keys I'm borrowing from one of my Unicomp keyboards. There was a spring/flipper in the right-side barrel, and an empty left-side barrel. All I needed to do was push a white stabilizer into the empty barrel, but instead I pushed in a black one. Learning here.
The final adjustment was that I had to change the voltage threshold to 123. At the initial value of 122, there were a few keys going off occasionally without any typing, and some ghosting from a few keys when I typed them. At 123, the keyboard has been completely stable since I made the change (an hour ago, so
This project and this keyboard are amazing!