If upon powering on your Vizio VS420LF1A the Vizio logo turns white, but the backlight does not come up there is a good chance the problem is in its main board.
If upon powering on your Vizio VW42LFHDTV10A the Vizio logo turns white, but the backlight does not come up there is a good chance the problem is in its main board.
If your Vizio XVT3D424SV LED TV initializes all right, but fails to start - especially if it starts back lights, but no image on screen - you better have your T-CON board tested and eventually serviced.