Vintage Synth Repair

>I have recently purchased a defective Siel DK-600, hoping that it
>might be an easy fixer-upper. Now.. what it does when I turn it on
>is.. almost all leds are on, the number display in the "program
>select" area is stuck at 00 no matter what you press and none of the
>other selector buttons seem to work either. Also the led by the
>"enter" button keeps blinking. So.. from what I told you what do you
>think might be wrong? The battery? It doesn't seem to be just a loose
>cable since all areas of the synth seem to be affected. Any hints and
>suggestions are highly welcome!

Ah, I've got one of these.  Broken of course, I think most of them are at 
this point.  Take the screws out of the bottom, open it up, and lift up the 
keyboard (it's hinged).  You will most likely find that the NiCd battery has 
leaked electrolyte and corroded some stuff on the CPU board.  You'll want to 
remove the battery and clean it up before it gets worse.  On mine the 
battery leaked and disabled the button scanning circuits.. so it turns on 
and makes sound but none of the buttons work.  Until I fix it, I'm stuck 
with a bad-sounding single oscillator saw wave patch.

Another thing that can go wrong (also happened to mine) is that the pitch 
bend potentiometer can short out and blow a fuse.  It's connected to the 
power supply rails, but it's some kind of funky center-tapped 4 terminal 
pot.  I don't remember the exact configuration, but basically when it wears 
out it will short to ground and blow a fuse.