Sega Genesis Crashes when pressing "UP" on P1 Controller.

If it's crashing, I think it's unlikely to be the controller. Especially as it works on p2.

Souhds like the logic that decodes the controller input to me. I will have a look at schematics when I get time for some suggestions.

 

I have a controller that also exhibits some odd behaviors. I cleaned the thing, but the pcb keeps registering weird things to the Genesis. I might as well go search for some busted controllers to do the pcb swap.