Is it possible
to use one of these VT420 to test a LK401 keyboard,
without
anything or anything too special connected to it?
Yes, no problem. Make a loopback connector, pin 2 to pin 3 on a db25.
OR In terminal setup (F3) Under communications setup, set local echo on.
Either way whatever you type will be displayed.
Picture tubes can be replaced, so hang on to the VT420's!
There is a good pallet load of them, and so far ZERO interest from this
list, so I have serious doubts to there future, excepting maybe one I will
play with. Thanks for the tip though, I really can use something to test
keyboards with.