I just googled your the Dual and it said it was belt driven. If the belt had not been replaced in several years you should buy a new belt. Also curious as to what cartridge you are using. The Dual table's tonearm are low mass and work best with a high compliance cartridge. You might want to try an Ortofon 2M or one of the Grado cartridges.

The table was also said to be an automatic ttable so if you are handy I would look under the top deck and see if the automatic mechanism still has some grease and operates smoothly. Another idea is to check the main bearing for the platter. It may need sone fresh oil but not the grease for the automatic mechanism.

Turntable Basics. Turntable Belts, Parts and Accessories. should have a belt if needed. Music Direct is a good source for vinyl along with bearing oil.

Have fun.