Thank you for your reply, I checked IC202 and indeed, its output is shorted to ground. Connecting the PSU, I measured the following voltages to ground:
pin 1 (VIN) = 5.408 V
pin 2 (VSS) = 0.0000 V
pin 3 (VOUT) = 0.0002 V

Checking IC1201, pins 1, 2, 3 and 24 (anticlockwise from dot mark) are shorted to ground.
​

Update: I have successfully dumped the 25Q40 firmware, which I attached. Alas, it doesn't seem to match the failure pattern of other models....

Hello, since yesterday our Samsung UE46F6400AWXXC no longer powers on, with the standby LED off. It turned off when someone attempted to clean it, not sure if related. A few days ago, there was a similar issue, but it was solved after unplugging and replugging the power. Additionally, another user of this TV reported issues of the screen turning off randomly, which were solved changing the channel.

I originally suspected the PSU, but if the mainboard is unplugged the PSU relay closes and the backlight turns on. It's only when the mainboard is connected that the relay doesn't close...

Hello, I'm an electronics hobbyist, found this forum trying to repair a Samsung TV