NOTE: In the oldest PS/2 PCBs and even older USB PCBs joystick 1 acted like NumPad keys. In the newest USB PCBs joystick 1 now acts like the arrow keys. So you may need to make changes to your software based on this. For MAME, the newest X-Arcade controller config file makes this change for you.
Before you begin, first use the instructions here to open the X-Arcade™ controller. Then check out our video for doing the upgrade:
If you removed more than one jumper at once and aren't sure where to put them back, check out the schematic diagram below for proper placement: