Ok, found my fathers ooolllddd CD player in the attic, and wanted to
use it.

It uses the KSS-210 laser, but it just won't budge.. At first, it
played a CD, but sounded very scratchy, then it gave up and said "NO
DISC" when there was one inside..

So, upon inspecting, when I insert a CD, it spins for a second, then I
hear a "clunk" and the drive just stops with "NO DISC".. Thing is, it
DID see a CD, because when there really is no disc, it will spin the
motor THREE times, where this it does spin up and the PLAY logo
appears, but it just gives up...

Diode gone? There's still a faint red glow from the diode.. I tried
adjusting the pots very carefully, and one way resulted in not even
seeing the disc, and the other made it play a CD, if the drive was
tilted at a 45 degree angle, though scratchy and skipping.