I was working on a SNES today, and I wired up a controller for it. And believe it or not, I had the same problem! the SNES worked After I Unplugged the controller.
And I was confused! were the pinouts I created wrong!? But alas, after checking them 4 times, they were not!
Confusing, eh? Well listen to this. I unplug the +5V line off of the controller, and the dang thing turns back on! I hate it! So I have 2 Ideas.
#1 The controller could be dead or Fried
#2 some unexplained problem Within the controller or the controllers ability to function.
SO My advice. Try another controller! I would, except I need to find one first

