Turntable plays 33.5 Lps very slow

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...

I have been experimenting with it... and I have noticed that the glass plate when set on the platter pushes the pulley down and keeps on touching the pulley while the table is turning... it makes a noise of glass and plastic rubbing against each other... so I put a rubber band between the plate and the platter to prevent the glass plate from touching the pulley and although it made the plate unbalanced it however did increase the speed (not 100% ok though)... I am thinking now of increasing the height of the shaft (platter).. is that a good idea?

thanks guys.. turns out that the pulley is loose from the motor shaft and its not set on it all the way down. All I had to do was push it down and viola!!! thank you guys for your time and your advice...