Why does my screen go blank

I've set up a print server based on Suse7.2 To save on disc space I'm using windowmaker, cups/kups and samba. I want the print queue to be visible so that kids can see the progress of their print job the screen goes blank after a few minutes of none keyboard use. I've checked the bios and apm and they don't seem to be responsible. Where do I look next? Dave Williams