Bought a brand new Samsung LN46C630 .Turn it on and sound comes on and a blue screen and the goes black. Any suggestions ?

This explains the issue you are facing

https://www.fixya.com/support/r29790007-repairing_own_television

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis. http://electronicshelponline.blogspot.com/ To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

Check and replace the back-light inverter board. It is faulty. There is no back-light now. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" will make surf easy.
http://electronicshelponline.blogspot.com/

its broken buy new one

t-con board

You probably have some bad buffer boards as well as a bad Y-main bd and or a bad X-Main bd. Have a trained samsung tech troubleshoot the set.

u need the main digital board for this model cost about $250 - $350

I have the exact same problem. Can anyone help?

> brand-new out-of-the-box

Presumably, it has a "warranty".

So, take it back to where you bought it, and demonstrate the problem to them, and make them repair/replace it, under warranty.