a Dreamcast won't load games

The optical drive works in a different machine though, loads games just fine.

In the machine it was in when I bought it, it just grinds and spins. Have any of you encountered such a thing?

I'm mostly just curious and looking for ideas, I knew it was broken when I bought it and have two that work already. I was just surprised when the optical drive worked in a different machine. I also swapped the power supply from the broken machine into a good machine (this was probably really dumb, don't do it).