nes advantage

[trigonometry3]

i recently purchased an NES advantage at a local gaming shop for 3 bucks and im trying to make it work usb through the good ol' keyboard pcb method, and i don't know a lot about this but the joy stick has an up, left, right, and ground wire coming out of it and i need to connect the wires to the keyboard pcb but with a common ground it short circuits some other keys that i don't want to be there.  Im thinking to solve this problem ill have to connect some diodes to the common ground and then to the pcb but im not entirely sure how it would work out.

Edit here are 2 pictures

[trigonometry3]

no one?

[solitary]

If I understand correctly you want to connect the buttons nes advantage with a keyboard to use it as the controller for pc ? ...if you can show clear pictures the nes advantage PCB from 2 sides (back and front),then maybe i can help you