out of range - new monitor

I got myself a new tft monitor, it works well in graphics mode (runlevel 5), but when I startup the system or try to switch to a console (tty1 or tty2), the monitor displays a 'out of range' message on a black screen. I can setup the monitor in yast for runlevel 5, but where do I setup the monitor for text mode? Thanks for your help peter