Ubuntu – How to stop screen going black after 10 min

My OS is Lubuntu 13.04. After 10 mins of inactivity the screen goes black. What I did to stop it without effect:

• uninstalled xscreensaver completely
• in power setting I set to never blank the screen
• run some command found in the internet with "xset" which was said to solve it (but maybe it was wrong command, if you know proper please write it)

And still nothing. I don't know why lubuntu wants so hard to keep going black when watching films. For example on kubuntu/ubuntu I just set in power settings to never go black and it works. Maybe lubuntu uses customized kernel with hard-coded extreme energy savings that can't be turned off?