SamyGO

Bad, but not critical. theoretically ExLink could be drop back to uart, open back panel and you will see the "magic button" on the mainboard.
If lucky, pressing and keep holding it drops your rs232 to debug. (check viewtopic.php?f=4&t=1952#p16865). Can be it just resets tv to reboot though. But worth to try.
If no button soldered, it is enough to make short circuit on those contacts.

Optional if you will fail, you always can buy another mainboard, replace it (yes, at home!) and this will cost you not so much as new tv.

I told you, I've two left hands related to Hardware.
Jesus, I never open the back panel!
A mainboard costs ?195.- and the change ?95.- without bring service.
A new UE40F6510 costs ?829.- and I have RC from Android out of the box and 3D without breaking the warrenty.

used mainboard costs up to 100 euro including shipping.
And replacing by self for free looking at YouTube video tutorial...

but is up to you. Anyway, apologies you've bad experience with samygo...

I've no bad experiences with samygo.
It was my failure alone.
It would be better I have some onsite support here.
I tried to contact dasolverpaladin from Munich over PM, but this seems to be dissabled for me (just to less postings?).
If you can contact him an he will grab his ExLink cable an visit me, maybe we can bring TV back to live.
Alone I'm compledly overextended. On any hardware related things.