Hi!

I recently got an ancient monochrome video monitor from a friend.

I think it might be OK to just plug it in, turn it on and go. I've done
exactly that with a number of old monitors that had been sitting for a long
time and had no problems. The overwhelming majority of "duds" were a result
of picture tubes that had simply been "used up" before the monitor was taken
out of service. I don't remember any offhand that died upon power-on.

As has been mentioned, some monitors have switch mode power supplies. These
may be stressed by low line voltage and they could fail either immediately
or after running for a while.

William