Samsung un46d6450ufxza does not show a picture on screen.

I'd look at a bad panel, the defective panel damaged your main, replacing that got it working somewhat but if it's on very long I'm guessing you will damage the main board you replaced. Try unhooking the ribbon connectors one at a time and see if half the picture works ok, if so you definately have a bad panel

is the picture possibly still there but very very dim shine a bright light to make sure if u see a faint picture and have sound then its the led lights that are bad

Samsung

Hi Dale, The link below is a YouTube video showing how to fix a Samsung television NO picture GOOD sound, Also there's videos down the right side of the link that may help as well........CHEERS..
https://www.youtube.com/watch?v=cI2L61dzj6k
Samsung UN46D6000 No picture Sound OK problem FIXED BN95 00497B BN41 01662A

Problem with the Samsung Digimax S730 Digital Camera the camera s 730 works poperly in doors but dosent take pictures outdoors ( after taking the picture it show a the picture as a white screen )

Does it look like this?
http://s807.photobucket.com/albums/yy352/budm/Samsung%20LN-T3242H/

If you tap on the main board, it may come back on.

This could be an issue with your DMD board or your Video Board. Go to the menu, if the white spots show on the menu, the issue is with your DMD board, but if they don't show, the issue is with your Video board.

replace the analog board

Try this. Go to your tools menu, look for something like power saver or display off and change the duration that the screen stays on.

try to reset the monitor to its default settings.