I made the update with version 2.25 using the firmware of the AOC itself and when I went to try to tune the channels using as the antenna a piece of wire I realized that no channel had been tuned and nor the sound had.

To get started, enter the factory mode (Menu + 1 + 9 + 9 + 9 + Back) and reset the settings.
Or change tuner settings (or change tuner type) in the service menu.
Then connect a normal antenna to the TV and try again.

If you can throw the firmware (U406 - W25Q64 and U406 - NAND) on the e-mail : Этот адрес электронной почты защищён от спам-ботов. У вас должен быть включен JavaScript для просмотра.

I got into service mode. Where do I check the tuner part? It would be where it says:

ADC
GAIN: R0 G0 B0
OFFSET R0 G0 B0

or

Scaler
Gain R122 G126 B114
Offset R512 G512 B512

The first is the ADC RGB adjustment, and the second is the adjustment Scaler RGB.
And you need to change tuner settings (or change tuner type).
But first you need to reset setting in the service menu (select and press "Reset" in the service menu).

And if it fails, select and click "EEPROM Init".
Then connect a normal antenna to the TV and try again.

I tested the TV, using the PC input, and the computer image appeared on the TV screen, so everything was perfect.

put a rca cable into the video output of a DVD player and the other end of this cable into the SPDIF input of the TV, the picture did not appear.

I am beginning to suspect that the main board is faulty, only replacing it.

And if this does not work, take the service manual and proceed to repair. Or try to reflash.

S / PDIF (Sony * / Philips * Digital Interface Format) is an audio transmission interface format that supports the transfer of digital audio signals from one device to another without the conversion procedure to an analog signal, thus avoiding degradation of sound quality.

In your case it is better to replace main.