Still looking for a spare adapter! I'm also looking for a previous version that uses a simple micro controller instead of the pro micro. It won't use the Soarers firmware or USB. But should work for your purpose, if I can find it! I'll have a little more time to dig this weekend.
Its an easy mod! anyone with a screwdriver can do it!!
boggit wrote; "Just to be clear, the only thing that would be needed for my use case besides your adapter, would be a passive PS/2-to-AT adapter, right?"
No, you keep the original cord which plugs right into the AT motherboard!
I'll have to see if I can find my spare one. Things are kind of a mess right now. I'm trying to move out of my house. It might be a while before I can even look for it. But if you're still in the market for one when I do find it, I will certainly sell it to you for a reasonable price. Probably...
I built a couple of adapters for that very purpose using instructions from a user named ENGICODER on the Deskthority forum. The link below is the GitHub for one of his designs. Everything (Pro Micro Arduino board) is hidden inside the keyboard!
XT2PS2 adapter GitHub
I like the looks of the PC better. The 5162 XT/286 is my favorite. 286 performance with the XT case. Although tall 16 bit cards won't fit, still pretty cool.
Oops! I saw the three at the end of the year and thought it was 23 not 03. Didn't really mean to necropost! Still the Soarer's converter is pretty cool. I have one in my 5155 keyboard that I hook up to a Pentium motherboard that's stuck in my second 5155 portable computer. Of course it's not...
Check this out.
https://deskthority.net/wiki/Soarer%27s_Converter#:~:text=Soarer's%20Converter%20is%20a%20closed,project%20is%20no%20longer%20developed.
You might be able to use the PiggyBack Method demonstrated in the following linked page.
https://www.minuszerodegrees.net/5150/ram/5150_ram_piggybacking.htm
Yep, that looks like the correct part. Unfortunately, looks like it's not in stock :-( I'll dig through my spare parts sometime soon to see if I can find one. No promises. I'm still working on trying to complete a remodel of my house. My vintage computer stuff is stashed upstairs and it's...