I recently joined the Alien club, and so started looking for spare I/O boards as I've been told those are a weak link. I reached out to pretty much everyone who might be selling them asking about stock. Everyone was sold out, and the responses I got from people who would know seemed to indicate there aren't any more coming. At least that was the impression I got.
I did find 2 boards from someone who "had a few left". PM me if you really need one and want to know where I got them. Not trying to be a gatekeeper, I just don't want everyone flooding that person's inbox thanks to my post.
I'm certainly not an authority, but I was recently involved in a board production run and I learned a lot. Basically, due to setup, component procurement, yield and so on, you're going to need to hit a minimum order size for it to be financially feasible. Of course every project is different, but in our case that minimum was ~200 boards. Do you think you could sell 200 I/O boards? I honestly don't know.
I think to guarantee long term support for these games, the community will have to invest time in understanding and documenting the platform. That way, when things fail they at least have a chance of being repaired. There is already a lot of good troubleshooting info on Pinside today, but I haven't found much about the I/O boards. Has anyone spent time analyzing them? Did Heighway ever share *ANY* documentation?
Edit: someone has indeed done the righteous task of analyzing and sharing their findings. Thanks to @Per_!
https://pinside.com/pinball/forum/topic/heighway-pinball-support-full-throttle-and-alien/page/18#post-4810082