My old science master built a TV from bits when he came back from WWII. 2.5" green picture. Open chassis, deadly EHT.
I went to visit him in recent years and reminded him that I'd given him five bob for the tube - a 4" electrostatic device.
'Yes', he said. 'We watched that for ages before we could get a new television...and for two years the picture was upside down.'