Died of PSU failure? Odds are one the components on the board was vaporized. An obvious sign would be a black mark near the PCIe power sockets.
Otherwise, any sort of burnt component. Failing that you'd have to go through each resistor and capacitor with a continuity meter to see if the component is OK or not. eVGA is not going to do that, though they do have quality testing equipment which can detect such failures in manufacturing so I would assume that they can also do that with a card that's been RMA'd.