Vintage Synth Repair

First off:  I have a Crumar Bit One in really nice shape except for 
the fact that there is a scratchy noise associated with the first 
voice.  Even when I swap the chips out, it's always the first voice so 
must be a problem with something other than the chip.  I'm wondering 
if this is common or if anyone may have any insight into fixing this.

Second:  I have a Siel DK80 that only seems to work when it wants to.  
It was working just fine one evening, but when I moved somewhere else 
and came back, the display was off and the unit would no longer 
sound.  When amplified, you can hear power running through it as you 
turn it on or off, but it won't light the display or output any 
sound.  I am wondering if this could be a battery issue, or if I am in 
deeper trouble than that.  If it could be the battery, I was wondering 
if anyone knew what kind of battery the DK80 took before I desolder it.