Does anyone know how to fix....

I got 2 console both model SCPH 50001, and they have the same symptom. Great!! When I pop the disc in, it makes couple of "click" sound and then spin very slowly. Not too long after that it finally come to stop. Again, 2 of my console behave this way, I have no clue where to start looking for the trouble. I hope someone here has an idea. Thanks.