To give direct video input another shot, I disconnected the output from the video detector to the 1st video amp, and injected a video signal to the video amp grid. I started with a B/W crosshatch pattern so that I could adjust the screen background, etc., to make a normal display.
Then I switched to a color bar pattern.
Adjusting the Color control, etc., gives nothing like a normal color-bar progression, so I'll check out the color circuits.
Phil Nelson