"BATTERY WAS CHANGED BECAUSE OF THE WELL KNOWN BATTERY PROBLEM THAT THESE CAN HAVE ,BUT THIS ONE WAS LUCKY THAT WE CAUGHT IT JUST AT THE BEGINING OF THE LEAK.SO NO BOARD DAMAGE."
Update via Jed Jorgensen in the comments: "(Shamelessly repeating this plug): Many a Korg Polysix has failed due to battery corrosion on the KLM-367 PCB. But don’t despair! Bring your Polysix back to life!
This plug is definitely welcome. Also posted here.