Take the rear cover off the tv, then look for swollen or enlarged capacitors on the power board. You can desolder the bad ones out, then re solder new ones in. It may sound like a difficult task, but it is pretty easy.
Hi there,
I was a Samsung tech for 3 years, and T-cons are a common problem. But it sounds like a loose wire to the T-con, I have came across the same issue in the field. I would break it apart and look for a loose connection.
Thanks,
Jason If you need further help, I’m available over the phone at https://www.6ya.com/expert/jason_70466cb634a57543
Main board is bad since it works with both video and audio. Ur backlights are ok so that omits the inverter board. And the T con board is for video only - since you have hassles with audio and video that leaves the main board. Do not think it is the power supply since your inverter board is powering up the back lights.