What fails on the AppleCD 300s (caddy)?

[eraser]

I have 2 Apple CD300 drives that refuse to read discs. For diagnostic purposes I can swap in a known-good recapped controller board and the drive will take the disc, seem to spin up, then eject it. Since I can rule out the controller as the culprit, what else might be bad on these drives? Laser diode?

 

[Durosity]

Could just be a dirty laser.. I've had at least a couple that needed that.

 

[Garrett B]

Try inserting the caddy with a bit more “umph”…. That’s made these more reliable for me.

 

[Byrd]

Weak laser, choice of media type and also check the belts inside if loose/stretched.