LED screen not backlit

I'm assuming I had a power surge because my modem is completely dead (no surge protector!). After holding the power button on the iMac there was a short alert/error noise. Sounds like HD is booting and sometimes all the fans start. Screen remains dark.

I'm in an old house that has less than perfect electric supply. I tried some other outlets

on different circuits-no luck. Seems like the screen is the problem. Any way to find out?