Discussion about the Korg PolySix synthesizer

Hi,

Just dug out my P6, and the voice buttons no longer function, i.e. 
you can press the buttons but the lights / voice does not change, the 
synth produces sounds, but no control. 

Had the cover off, no battery leakage anywhere, any ideas?

I think it might be a CPU problem, I am thinking on doing the MIDI 
upgrade [not sure of the name, but it replaces the CPU board] so if 
you guys think it's a CPU problem, I will go down the MIDI upgrade 
route.

Thanks in advance for your help.

Sean