Chosen Solution
Samsung UN70TU6980FXZA 70" Class TU7000 LED UHD 4K . Has sound, backlight works, black screen (very dim blue glow from backlight). Figured it would be the T-CON board based on my research. I opened it up, no T-CON board (that I could see). I thought maybe the T-CON board is combined with the main board so I ordered that for $40, replaced it, no change in behavior. There are three skinny boards at the bottom, somewhere I think they were called “address boards”. Are they the same thing as T-CON boards? Or is the T-CON on the flip side? The problem with the skinny boards is that they seem like they might be permanently connected to the panel, seems like no practical way to replace them, the ribbon cables are soldered/glued on I believe. Am I out of luck fixing this thing? It’s only a couple of years old.
Mark Krueger you are correct. Your main board has the T-con circuitry on it. It is the same board. Let us know how you determined that the backlights are working. The safest way to test this on Samsung is to remove the cable from the power board to the main board. That would turn the backlights on. Since you already changed the main board (with the T-con board) it can be ruled out. You should also test the voltages on your power board where the backlight LCD’s connect too. Let us know what that voltage is. The boards you pointed, to are the LCD driver boards and are not DIY replaceable since they connect via fine ribbon cables to the LCD panel.
