I can find no way to completely turn off the display on a late 2013 iMac running 13.10 (Saucy). In the power management settings, I configured the display to "turn off" after one minute to see what would happen. The dimness goes all the way down and everything disappears, BUT the LED backlight remains on. When I try the "xset dpms force off" command, absolutely nothing happens--the command is accepted (no error or warning), but nothing changes.

I then wiped everything clean and installed 13.04 (Raring). Both methods (dpms and waiting for sleep) work perfectly there, so something has changed in this new version.

The problem can be replicated simply by booting from a bootable USB stick. So, I also gave version 14.04 (Trusty) a try in this manner and it has the exact same issues as 13.10.

P.S. I would gladly use 13.04, but the catch there is that I can not get the network card to function. I have spent a week now reading everything i can find on both of these matters with no luck at all. Thank you in advance for any advice.