Hi Chris,
Yep, sounds like a main board fault. Samsungs should have a test pattern generator on the control (logic) board which will confirm if it is the main board. You need to disconnect the LVDS lead from main to control, disconnect psu to main at the main and short the PSU-ON pin to ground (return). Apply power and short out the generator pins on the control board. If you get test patterns, then the TV, apart from the main, is all operational.
Haven't had much luck cooking Sam boards, mostly seems to work with LG. Must be something to do with LGs soldering techniques for ball joints.
Anyway, election's on and a few more terrorists gone to wherever they go. Bruce