How can I stop rumbling noise from my Pioneer PL-J210 turntable?

If you spin the platter by hand, with the power off, it is probably the spindle bearing. If this bearing loosens, the platter may be scraping against the plastic base. Try tightening the nut nut at the base of the spindle bearing. If this does not work, the bearing may be bad. If you're in the USA, and need more assistance, or would like to inquire about a repair, please visit my website at audioserviceclinic.com. Thank you.

Well looking at the newprice, i would buy a new one/, but you have a belt drive platter and it it works as easy as a carengine - and the belt which turns the transformer, which goes via pullies which maybe in your case is just worn out, but first try a bit oil. And check the belt quality. If it is the motor, which i doubt , i wouldnt put any money in it , since they the unit is 60euro new.

greets holland