I'm running Fedora/KDE 23 on a ThinkPad T510 laptop.
If I leave the laptop open but idle for about 5 minutes
the screen goes blank, and I see no way to "wake" it.
The laptop seems to be alive, as the WiFi LED is flashing,
and Ctrl-Alt-Delete causes the disk LED to flash briefly.
I've tried everything I can to wake the laptop,
including many combinations of Fn, Ctrl, Alt and F*,
as well as what I take to be the SysReq button.
But the only solution I have found to date
is to power-off and power-on again.
gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin