Turntable plays 33.5 Lps very slow


Hi.. guys all my 45 rpm Lps are playing fine , but as soon as I change the belt to suit the 33 1/2 rpm Lps, it slows down to almost half I think. Its deadly slow. It couldnt be the motor since the 45 rpm's are all fine... what could it be?
akhan
Is this something that just started recently? What table? Does the belt slip? Does the motor bog down? have you re-lubed the shaft? How old is the table? More details!

Jim
actually I just got it...used.. its rega planar 3... i tried cleaning the pulley and also put powder on the belt and now both 33.5 and 45 rpm are runnign slow :)
also I dotn know how old it is.. how do I check if the belt slips... and how do I know that the motor bogs down...