I powered on my R720 after 2 months (it was also unplugged from the mains) only to find that the fans are spinning at full speed, front LCD panel does not work (is dead) and output via both front and back VGA is scrambled/corrupt from the BIOS screen onwards. It does not even get to the OS.
Scrambled display output:
Before all of this happened, the system had the latest firmware and bios updates as of September.
Troubleshooting steps:
-Reseat all raiser cards
-Reset BIOS via jumper
-Reset BIOS via taking the battery out
-Reconnected LCD panel board cables