Rise from your grave!
Thread ressurrection!
I got the PROM from steph (quite a while ago, actually) and got it installed, unfortunately this board had more wrong with it than just a missing PROM. I built an adapater to test it out and found that the graphics were all blue and really scrambled, since I had other projects I was working on at the time I shelved it until later.
Welcome to later!

I saved it for a rainy day and since there is heavy cloud cover and downpours in the forecast here in St. Louis, I'm ready.
So far, I have replaced the 4016 at D2 and the currupted graphics have cleared up, but the screen is still only blue. I have determined that I need the other two color PROMs replaced as well. Steph, your PM is coming.
Now for the final issue: there are no character sprites. The game will coin up and I can play the game, the background scrolls past, I can hear my shots when I press the fire button and the game behaves in every way like it is working. I can even score points when my invisible plane fires invisible shots that strike the invisible enemies. So far my best score is 950 points! (not bad when all you see is a background)
I am going to keep at it tonight, just wanted to see if anyone else has some ideas to throw out there. I will give a repair log type recap at the end for the refrence of anyone else trying to repair this board.
Brian.