this is the assembly service to modify your korg keyboard.
The input is for a analog Clock signal, which means just the speed signal without start/stop commands.
It´s perfect to have the same clock as a SH-101 for example.
I offer a clock input as descibed:
https://dsl-man.atlassian.net/wiki/spaces/DSO/pages/1147638/Arp2600+keyboard+3620+clock+input+Modification
you have to send only the controller with panel to me, on your own costs.
you have to remove the controller from your keyboard, by removing few screws,
you get an instruction of the removing from me,