Spindle motor serves to rotate the disc. The data in the optical disc is read by then piloted by ic motor. Range impedance in the motor a good 10 ohms - 12 ohms. Can be tested manually by turning the spindle head. When the round was light then the conditions are good, whereas if the rotation is rather heavy and coarse then it should be replaced with the same type and with good quality. This is to outsmart many spindles using regular motor home for dvd player, but most do not take into account whether or not the head of the spindle flat. The slope of the few causes a shaky rotation and finally optics can not read data with a maximum. . And just info, the market there are different types with different qualities, it should use good quality parts.