I have a UN75Q6FNAFXZA 75 inch 4K TV that stopped coming on. I am an electronics tech by trade and since the TV is out of warranty, I decided to do a self diagnostic. I found the fuse blown and multiple burn marks on the power board. So I changed the power supply board. Now that I have power to the backlighting LED, I got a startup and power down cycle. After unplugging all forms of outside connections, I only have the mainboard and the Power board connected and the TV comes on with no power down, but I also have no picture. I have diagnosed down to the two ribbon cables on the right side of the main board. If I disconnect either cable, the TV will start up with no picture. If I plug them both up, the TV does a power loop. My question is: Since my TV doesn't have a separate Tcon board, can the LED driver board cause I power loop or it the mainboard just failing to make the proper connections to allow it to work?
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