I just picked up a UN60JU6400F on this Thanksgiving for $800. After messing around with it I was slightly disappointed by the omission of 4:4:4 chroma @ 4k 60hz. A quick google search revealed the this is only possible on the 6500 and up, after comparing the specs and reviews of these TVs it became clear to me that the 6400 and 6500 are essentially the same TV but with a more populated motherboard and bluetooth. I decided that the upgrade was worth the risk and found the 6500 motherboard and a wifi/blueooth adapter on ebay for $45 with shipping. When it arrived I opened up the TV and swapped the motherboard, unfortunately as I only received the boards and no cables I was unable to upgrade the wifi/bluetooth card as the wifi cable inside my tv is missing over half the pins (cheap bastards!). After putting everything back together It booted up and works great (aside from some minor color calibration adjustments). However as the 6500 expects a wifi/blueooth adapter and all I have installed is the wifi one, the wireless is currently non operational but Ethernet for now is fine for me. (I did see resistor bootstrap configurations on the motherboard to allow for my original wifi card and a few others but would rather use the new and intended wifi/bluetooth card)
I know that this information is not news but just wanted to let anyone who has the 60" version of the JU6400 (probably other sizes and the JU640D/JU6390 as well but I cannot say) know that it is possible and works great (at least for me, please don't hate me if it doesn't work for you), and if anyone wants to upgrade I would suggest doing so while they are currently still cheap on ebay, they probably will not remain so when this TV goes out of production.
I do have one question however if anyone knows the part number for the cable that the bn59-01194f wifi/bluetooth module uses or even better, a pinout and the connectors used so that I can just make one myself instead of buying one for an insane price?
Oh and this probably goes without saying but only do these types of modifications if you know what you are doing and at your own risk, I am not responsible for sad non functional TVs!
Picture of original board installed
Wifi cable with missing PINS!!!