I did the soldering for the keyboard for our arcade machine. It has 27 wires and it's separated into 2 set, column and row. So, we have 18 columns, lets say column is A to R and Row is 1 to 9. When we press Y, it connect the row E and column 2 together, then the signal from the keyboard will be sent to the PC. Here is the photo of the keyboard chip.
We are planning to complete wiring the keyboard logic board to the controller the end of this week.