turntable spins at 45 but not 33 - any clues?

I am looking at a Thorens td110 (not the best thorens model
I realize). Anyway, it spins fine at 45 rpm, but doesn't
spin at all at 33rpm.

What is likely to be the problem? Will a general servicing
fix this or will I need to find rare and obscure replacement
I'm not familiar with that particular 'table but some require you move the belt to a different section of the platter or even a different drive pulley to change speeds. Take a look, that may be the case. Best, Jeff
Yes, on some tables you have to lift the platter and move the belt manually to another groove either under the platter, or on the motor.

If your table has a switch on top, maybe it is stuck or broken, but you may be able to move it manually anyway.
If I am correct the table has a switch that selects the two different speeds. When you switch it to 33, there is a divice that lifts the belt. Try to see if that little hook that lifts the belt is functioning. I had the same problem once on what I think was a similar Thorens and i just manual lifted the hook and it worked form there, it probably was a little stiff.

You should have a little "lift" that the belt sits in between. Lift the platter and make sure the belt is sitting in the lift or it wound move the belt.