I got an old G4 from eBay that was having logic board problems. This afternoon I took off the bottom plate to try to re-solder the chip that seems to most commonly be the problem. After completing the procedure, I put the heat shield back on the bottom to protect the bottom of the board to flip it right side up. I plugged in the power cable and I pushed the power button. A spark flew from the metal frame to the heat shield and everything went quiet. The adapter is no longer glowing and I can't get any response. What have I done and is it fixable? I'm super bummed, so any help would be enormously appreciated.