Hi, I'm working on a mac with little success. Any advice would be appreciated. Macbook Air a1369 Computer displays white screen when powered on. No chime, no other screen activity. Seems unresponsive to any keyboard boot commands, i.e. Option-Command-P-R have tried all available boot commands There is no obvious physical damage to the computer Was noted that the computer slowed and locked up before going to white screen. Anyone else run into a similar problem?