DPMS is specified in your /etc/X11/xorg.conf. Usually a simple
in your Monitor section should suffice, but if it isn't working you may wish to try adding a section like the following:
Code:
Section "ServerFlags"
Option "blank time" "0"
Option "standby time" "0"
Option "suspend time" "0"
Option "off time" "0"
EndSection
Of course, change "0" to the length of time in minutes that you want. See `man xorg.conf` for more details. If it still doesn't work you could try running `xset +dpms` or some such thing and see what happens.