2 I too replaced the mainboard and powersupply
I am facing the same issue with my Samsung KS8500 , looks like it is the panel issue, I too replaced the mainboard and powersupply . I had checked all the voltages from powersupply and they were all correct , but just to take a chance changed the powersupply as well, it still having the same issue.
These TVs do not have any T-Con boards , they are part of the panel , so if T-Con is bad, there is no way to fix this.
Update (07/29/23)
It is the same issue as the OP posted in the thread.
"As of now, my after turning on my TV, I can see the backlight turning on for a second or two, then turning off for a second or two, and endlessly repeating this cycle."
I have tried changing both mainboard and powersupply and still facing the same.
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@bx2sms what is the issue with your TV? What does or does it not, do?
door oldturkey03