This arose from a conversation with my brother in law who is a musician, he was talking about people using "TV tubes" as guitar amp valves - without realising he really meant valves from TV's back in the day. But anyway it got me thinking about it.
So my two trains of thought were running it with no EHT as dp says, or with EHT but very unfocussed so the whole screen gives a gentle glow, which might visibly vary. I know when I messed about with CRT's in the long and distant past I had full screen glow happening when I wanted a spot.
I think I saw your radar screen thread dp.
Lissajous figures would be cool
The next question is, how do you run a valve in current mode? It had never even occurred to me as a thing...
My OTHER other thought on visualisation was to generate a raster and see if any visible patterns develop. Of course then you have the problem of the scan signal getting back into the audio.
I wonder how well A1 and A2 would be at acting like pentode grids G2 and G3?
But first I have to get the old TV off him...
My next other other other thought is it's a colour tv so I get 3 guns to play with