Just for the record and to help people to solve this problem, goes what i did.

taking a previous post as a start, I turned off dpms from the options in kde (control center) and gnome.

but this didn't really solve the problem, then i went to xorg.conf, and comented 2 of the 3 lines that set the times. i just left the option "off time".

# Option "standby time" "0"
# Option "suspend time" "0"
Option "off time" "25"

since i'm using Xfce, i put an Autostart script with:

xset dpms 300 300 900

notice that this command means that in 300 seconds (5 mins) the monitor goes into standby. 300 seconds later (another 5 mins= 10 mins) it goes into suspend. 900 seconds (15 mins) later it turns off the monitor.

hope this helps.