Need to know what the back light inverter looks like on a LED39B45RQ RCA TV

http://www.specsserver.com/CACHE/FRXSWBMUJWAT.PDF

https://www.diyforums.net/rca-led39b45rq-39-power-issue-139866.html

What boards did you replace? Not knowing what you did it seems tv set is dead and that it just may be a power supply issue, a common ailment.

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 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.

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.

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/
In some models of LCD TVS; the backlight inverter and its T'Con board will be a part of the panel itself, and will be a built-in type inside the LCD panel. If so, they can't be replaced. In this case; a panel replacement is the only repair. For some other models, the backlight inverter section circuit will be a part of the main power supply regulator [SMPS]. To such sets, the power supply section circuit too should trouble shoot. Contact any service technician. The circuit will differ with models and versions.

look in ur phone book under electronic there might be a tv repair shop or just do a quick google search or just buy a new one