White Screen no apple logo
2007 20" EMC 2133
White Screen: I can access the internal HD via (T = Target disk mode) all is well there. The external monitor does not work via mini display port to HDMI. Also have exhausted all Startup commands. Also unhooked the internal HD to try to boot from DVD zilch. Wont boot (via option @ start) from USB stick or DVD will spin up but zilch. My best guess is the video card. Could it be the logic board or LCD issue? Also there is a dark gradient from the bottom to mid screen. This was happening prior to the white screen of death. Any help or thoughts would be appreciated. Thanks in advance.