Where can I find a power board part # BN44-00717A for my 65" Samsung smart tv ?

Without getting all technical your LED backlights are bad, the part of unhooking one ribbon cable and not having the repeated cycle would be normal in this model set.

Is it a LCD or LED set?

1. open the back cover of the TV, disconnect the cable between the main board & the power supply.
2. Apply the AC power to the power module, if the back lights are not light up, change the LED strips (IF the back lights are bad, in some case, the power supply also been damaged), If the back lights are light up, please change the main board.

It's the motherboard in the tv, you Will have to get it replaced, if you have warranty still, then you'll be fine if not $165-$185 for replacement, (your Samsung warranty will cover this). This is exactly what happened to me

Hi!


Check your power amp circuit. Or, check if it is feed by the power supply circuit. Good luck,


Serge.

Check and replace the back-light LED strip. Contact any service technician. http://electronicshelponline.blogspot.com/

http://www.cnet.com/forums/discussions/samsung-smart-tv-turning-off-609897/

obtain warranty support before trying to diagnose or repair

Here is what to check when your TV is turned on, power light is ON, but no picture is seen or sound is heard:

1 - Be sure the component you are using (Xbox, Cable, SAT, ROKU) is turned ON.
2 - Check to be sure all cable and cords are securely connected to the TV inputs and component outputs.
3 - Make sure you are on the correct input as some TV's will show a black screen if there is nothing connected to that input.
4 - Unplug the input you are trying to use from the TV (such as an HDMI Cable) and plug it back in.
5 - Check for signs of damage on all cords and cables from the TV to all components.
6 - Make sure the TV is not in ENERGY SAVE MODE, press the button on the remote control to go back to normal mode.
7 - Unplug the TV for 10 minutes to see if there was a temporary one time issue with the TV.
8 - Disconnect the TV from power for 2 minutes, then when plugging it back in PRESS AND HOLD THE POWER BUTTON ON THE TV FOR 10 to 20 SECONDS to try and force the TV to reset.
9 - If after checking all these different issues, you may have a Faulty Power Supply Board, A Bad Capacitor on the Power Supply Board, Loose Wire Harness, or Loose Ribbon Connector in the TV itself.
10 - Most likely when a TV has the power light ON but NO PICTURE and NO SOUND, it is the Power Supply Board that has failed.

BTW, here are solutions for you to play iTunes movies on Samsung smart TV

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/