To get a feel for what's involved, look
here.If it's just the joystick direction (up) that's not working, then I'd suspect the 74HCT166 (U975), one of the EMI beads, or maybe the pull-up resistor pack. As Antony mentions, it may also be a battery that corroded some of the traces when it leaked. All the info is there - have a look.
banzai
