얼마전에 st-4를 중고로 구입했습니다.
다까하시나 빅센은 오토 가이더 배선연결이 쉽던데 제껀 켄코라서 배선연결이 쉽지 않군요.
인터넷을 뒤지다가 켄코 핸드 컨트롤러에 st-4를 물려서 쓰는 사람을 발견했는데 그사람 답변을 읽어봐도 회로에는 까막눈이 되서 어떻게 연결해야 할지를 모르겠습니다.
그사람 답변과 기판 뒷면 사진을 보내니 힌트라도 좀 주시면 고맙겠습니다.

Hi Jung,
thank you for the comments! There is a simple way to connecto Kenko NES to ST4, you need to build a cable with at, an end, a ST4 connector (Reley Connector, 15 pin) with
pin number        function  (see ST4 manual, appendix A)
11                     +X, common
10                     +X, Normally Open (NO)
5                       -X, common
4                       -X, Normally Open (NO)
14                     +Y, common
13                     +Y, Normally Open (NO)
8                       -Y, common
7                       -Y, Normally Open (NO)
At the other end of the cable (simple 8 wire cable) you need to join with a welder the wires to the buttons of the Kenko NES handpad (remove the cover), better if you make a hole in the lateral part of handpad for let the cable pass. Then place the cover on it's place.
The +X cables need to be joined to the right button, -X left, +Y up and -Y down.

Obviously be aware that this modify will void the warranty, but if well done it will not damage anything and will be forever.