As i watched my LG last night it made a rather loud pop and shut down, the audio came back but no video. Any thoughts

Replace the mainboard

Well, that means something got realy hot under load. could be the main i.c. under the heatsink on one of the sustain boards. look for cook marks or discolorations on the backside of those boards. could also have been some condensors somewhere that popped but usually it wont be loud enough to hear and they may whistle instead and usually on the power board.

if the i.c. on (y-sus) popped on ya. it may have blown the upper and lower buffer boards it has attached to it. check with a meter to verify they are good or shorted (constant beep)

good thing is, lg has alot of boards out there.. shouldnt be a problem finding what you need.