KawaiK3Zone

Sounds like you have a bad voice. Could be one of the filter chips, or  
it could be something else.

Some of the chips are replaceable, and using an IC extractor/insertion  
tool, you can pull out each one and reinsert it to make sure the  
connections are good. Finding the schematic online shouldn't be too  
difficult so you will know which chips are relevant, but in general if  
you look inside you will find that there are six groups of chips that  
represent each voice. Look for other kinds of damage to the resistors,  
capacitors, and circuit board itself. Sometimes corrosion, or a dead  
battery, can destroy nearby components.

As cheap as a K3 is, you might find it more convenient to find another  
one. I used to have a K3m with the same problem and I eventually just  
sold it on eBay because I already had another one as well as the  
regular K3. -pc