For almost a year, I’ve had a CDJ-100s that my brother inlaw gave me to repair. He picked it up second hand from his employer as broken, and was hoping I could fix it. Basic troubleshooting showed it wouldn’t read disks. You’d put a disk in, it would spin up, but then never show track info, or start playing. I did find the Service Manual online several places (linked here), but beyond basic troubleshooting, it required the “YEDS-7” disk, which is also called the Sony Test Disk 3. Which costs, from everything I can find, at least $150 (and has also been discontinued). So, it sat in my repair pile.