Tony, G4CJC, one of the keen Data mode operators and of the 10 metre page on the Southgate Site. Has sent in to share some issues he has had with the Screen and power save functions on his PC.
FT8/FT4 and “screen savers or power savers”
This is a short article which could explain a phenomena that you may have 
experienced. It affects FT8, FT4 and maybe other data modes. The following 
happens after a normal start up and transmitting/receiving session of any length. You
leave your computer still switched on with FT8 running and go away to make a 
tea/coffee/sandwich whatever. When you return the computer screen is blank. Ah, 
you think, the screen saver has come on. When you move the mouse or touch a key,
the picture returns and FT8/4 is receiving as normal. Till you try to transmit! The 
radio will key up but no data goes out. This is reproducible. In Control Panel I tried 
setting all the USB ports so that they could not be powered down but without 
success.
There are several work rounds. One for WSJT-X is to go to Configurations and 
“switch to” a copy Configuration you made earlier. You did make one didn’t you? Or 
you could close down and restart WSJT-X. But the best thing to do is to go to Control
Panel, Power Options, Chose or customise a power plan, Change plan settings, Turn
off the display. Set Turn off display to Never. Make sure that it is Never for each plan 
you might use. Now the screen will stay on all the time. So you may want to set a 
screen saver. Go to Windows button, Settings (gear near bottom left), 
Personalisation, Lock Screen, Screen saver settings. Now if you are like me and you
don’t like swirly coloured patterns across your screen you set Screen saver to blank 
after a suitable time. Might be a good idea to restart the computer at this point.
Of course, the real easy way to save power is to press the off button on the monitor. 
This works whatever OS you have. Just for information mine is Windows 10 Home, 
version 1909, x64 based system with all Quality Updates to 22/04/2020.