Korg DW8000, Mono/Poly, MS-20...

Hi!
I just purchased a DW8K.  Everything seemed fine, but when I got 
home, I found out that the DW8K is out of tune.  I've tried to 
fiddle with the "TUNE" slider, no effect.  
I put a little bit of contact cleaner and opened it up to check with 
an Ohmmeter.  The slider works fine (I got values from 7K to 97K).  
So I'm wondering, since I don't have a user's manual, if there's a 
key I should hold down while I'm move the slider or some trick of 
the sort to set the pitch straight?

Thanks!

Alain