I recently acquired a mac book air from a pawn shop and it was working & I tried to reinstall the operating system with the only (unibeast multibeast?) install usb that I had available (no net connection when I was working with it) & came across information online that stated I'm supposed to select UEFI at the boot screen & after I did the apple logo did show up but nothing happened. After about 20 minutes of waiting, I forced rebooted now the laptop screen lights up with a dark screen & it constantly restarts with the mac startup chime. I took it to the apple store & was told that I need to replace the logic board & the asking price is almost what I paid to get the laptop. I know there could be a simple fix but as of right now its dead in the water. Any help would be tremendously appreciated.