I used too high of a voltage on my GameCube , how do I fix it?

John zoidberg this will depend on how you powered it up. When you say you "forgot to use a power converter" I assume that you are somewhere where the voltage is not 110V. You usually plug the GameCube power adapter into the power converter. This time you did not and your GameCube no longer comes on. This would lead me to believe that you have blown the power adapter. To be certain we would need to know for sure how you usually power it up, what voltages you are dealing with and what voltage your GameCube power supply has.

Since you applied 220V where there should only be 12V you are most likely having multiple damaged components as well as probably a burned board. You will have to disassemble your GameCube to take a look at the boards. Start with this guide Nintendo GameCube Motherboard Replacement and take plenty of pictures. Post those with your question so we can see what you see. If you are lucky the damage will be contained to a single board only.