How to set TERM for Televideo?

[daisy basto]

Hello, can someone shed a little light on how to set up a terminal?
I'm trying to use an old Televideo connected to tty0 on a serial port.
After I logged on and set TERM=tvi950, the system still cannot run any
screen-oriented programs such as vi. When I try to edit a file with vi
it will respond with  [Using open mode]. Most other commands run fine.

I can see the termcap entry for the Televideo in /etc/termcap. Is there 
something else that I need to do to make it understand the new TERM entry?

Thanks, Daisy.