Vintage Synth Repair

>Ok.. I have just opened it up. I see the battery and it looks like
>there's some kind of corrosion or brown stuff around the solder points
>  on the board but can't really see much, I'll have to take it
>completely out and put some more light in here. How do you clean that?
>What kind of solution would I have to use? I am kind of hesistant
>because I'm afraid I'm gonna destroy some of the traces on the board.
>By the way my synth does not make a sound at all, it just lights up.
>About the "exploding" mod poti... how can I work around that? What did
>it to your synth when it happened? Is there a way to ground the pot
>elsewhwere other than over the power supply?

The problem with leaky batteries is that the electrolyte solution corrodes 
the board traces and messes everything up- you'll have to replace the 
affected components and somehow rewire the corroded traces.  There's a 
repair guide here for the Polysix, which also uses NiCd batteries.

I'm not sure about the pitch wheel problem- on mine it shorts out when in 
the center position.  I think I stuck a resistor or something in there, it 
messes up the pitch wheel response, but okay for a temporary fix considering 
there are bigger problems right now and I don't really care for pitch bends 
anyway.  If yours is okay now then don't worry about it, but if the fuses 
blow suddenly for no apparent reason, it's worth checking.