A:Answer I have the Samsung UN55F9000, which had the same problem of not showing 4K on the screen. I researched this on the Internet and purchased the SEK-3500U to see if it would truly upgrade the picture and TV. It does enhance the picture greatly and allows for 4K. One caveat is that if the 4K is 60fps from the source (Xbox One X) then motion blurring is turned on by default and cannot be turned off. Not a huge issue and hopefully fixed in the next firmware upgrade.
I should point out that there are proper steps to switching out the original box and installing the SEK-3500U, which are below:
1. Update the firmware on your TV.
2. Menu > System > Evolution Kit Backup (run this even if you don't have an evolution kit or one connect box attached).
3. Completely power down your TV. Unplug the power cord and depress the (joystick) power button on the back of your set to ensure that all power is dissipated.
4. Connect the SEK-3500 to your TV and reconnect the electrical power cord.
5. Connect antenna, Ethernet, HDMI and USB cables directly to the SEK-3500.
6. Turn on the tv and follow directions.
7. If you are using a Bluetooth remote, you may need to (re)pair it to your TV.
Alternatively, you may simply need to reinstall the apps that aren't performing.
Additionally, some have reported that the internet experience on the set is remedied by changing the DNS from automatic to 8.8.8.8