I've been working hard lately, repairing many Sega CDXs and (more importantly) documenting it all! You could follow along through my new playlist here:
https://www.youtube.com/playlist?list=PLLO0V62qHnydQDeSwAY6c8awcJTK37iKx
Also, I'm thinking of adding a super detailed Sega Genesis / Sega CD repair guide to my website. Feel free to share your thoughts if you think that would be helpful.