7.1 text-based on RS6K

I'm using an IBM 3153 ASCII terminal connected to a RS6000 B50 to install 7.1. Unfortunately, the screen does not refresh or display correctly and becomes unusable after loading YAST. I've experimented with different setup settings (Emulation, AutoScroll, etc) and I've had no luck. Any suggestions for setting up a terminal to use a text-based install?