How do I make macOS properly blacken my TV screen on standby

Solution 1:

The message "HDMI 1 (Clock) No input. Check your cables, etc." is apparently generated by your TV. The first place I'd look is in the TV's menu system. See if there's any way to change what is displayed when there is no incoming HDMI signal.

If you can't find anything there, you can look at the Sony website. Note that there's a firmware update available for you TV as well. There's a chance you'll be able to control the "no input" message more easily after the update.

https://www.sony.co.uk/electronics/support/televisions-projectors-lcd-tvs-android-/kdl-43w755c#manuals

But, what you really want, I think, is to set up the Mac Mini so that it shows a blank image as its screensaver.

Solution 2:

Another way to approach this is to try (again?) to set up the TV to shut down when the HDMI signal goes down. It may not be possible with your model, and I see where some Sony TV owners are complaining about that. I did find an answer that has a chance of working for you, but I found it through an archive of a forum page, so I'll just copy and paste the (paraphrased) excerpt:

There is a setting on some Sony TVs called Auto Shut-off wherein the unit will turn off when no input signal is detected for 15 minutes. To access the Auto Shut-off setting follow these steps.

1. Press the Home button on the supplied remote.
2. Press the Right or Left arrow button to go to Settings.
3. Under Settings select Preferences.
4. Under Preferences select Eco.
5. Select Auto Shut-off then set it to On.