Also, check that the laser moves along the runners freely, a problem I had. I used butter cause I was too lazy to pull the runner out, clean it, go out in the freezing cold and get some proper grease stuff.
But yeah, check them.
I think Sony poorly designed the little white plastic bit on the motor.
My PHAT PS2's been through hell and back, I've replaced loads of parts. Even the USB ports went, but I soldered some on from an old motherbaord from a PC. Still chuggs on with SWAP MAGIC and a USB hard drive though.