Casio CZ/ VZ/ FZ - Pro Series

Hello,
I just bought a beautiful Casio CZ-1 at a pawn shop for $85, but it has 
some issues.  It won't make sound unless I slide the volume and chorus 
around a bit.  Then the sound fades after a few seconds, and I have to 
switch it off and on again to get sound.    

All buttons power up and seem to work fine. Display work fine as well.  
I'm almost sure the problem is in the chorus circuit as it seems to 
affect the volume.  It could bad capacitor, but it could also be a 
short.  

Does anyone have any suggestions of where to start?  

Thanks for your help,

Roland