I replaced logic board on my UF75F6300AFXZA BN4400621C. Worked for 1month then started power cycling again. Got a power board fix on eBay that changed capacitors. Worked for about 2 months. I contacted the repair service from eBay, and they told me to reverse the cable that connects the logic board to the power board. It worked for about 8months. Now the power cycling is back. I find that if I hit the tv in the back a couple times, it stays on, but will occasionally turn on and off. No more samsung televisions for me.