Comment # 11 on bug 64850 from Alex Deucher

(In reply to comment #9)
> Ok, i tested a few things:
> 
> Turning the monitor off/on dosen't do anything, its still black.

sorry, I meant using xrandr; e.g., 

xrandr --output DVI-0 --off
xrandr --output DVI-0 --auto