Maybe a service manual would do good, or maybe your friend that took the keys from the other KN could guide you how to replace?

The servicemanual would be good to have, but unfornately I dont have any.
Another long shot could be to ask Walt Tenay if he still have the servicemanual avalable?

http://www.synthzone.com/forum/ubbthreads.php/topics/395521/Service_Manual_for_SXKN2400_an

But, it's quite a long time since this post was published, and I have not seen any post by Walt for a very long time.

Last post was September 2015 as far as I have found out by a search:

http://www.synthzone.com/forum/ubbthreads.php/topics/408097/
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GJ
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"Success is not counted by how high you have climbed
but by how many you brought with you." (Wil Rose)