I have only one CRT that play all my pre 480i signal system well, a Sanyo TV flat screen CRT (and my 1979 Hitachi that do a bit of color bleed and can't be seen well now in the day as the black is now light gray). If that one die i am screwed.
On a Sony trinitron (and my RCA-thompson TVs) only the C64 display ok (perhaps that is 480i also). All 240p system show different "dotted" horizontal section 1 pixel high that seem to be influenced by color or contrast (on edges mostly). In 2600 pacman, the first line of the screen is all doted and some pixel can be seen in some places. In outrun on genesis, the top line of the windshield is dotted.
I can't seem to find a solution to allow all my systems to display fine on all my CRTs. It's already a pain to shop for one, imagine shopping for one not creating the problem. Trying to pass the signal into VCR don't help.
I suspect some kind of interference with 2 identical line of a 240p signal with a slight delay between them. I can't seem to see signal processor for sale that do 240p composite to 480i composite. I also only see 240p to HDMI and never 240p to 480p without and hdmi out. Lot of my CRT (later ones) have a 480p (component connections) even if they are 4:3 but i would love a solution for those that are only s-video or composite IN.