All the guides I've checked for modding console with component (YPbPr) output suggested I test by plugging composite to green input to check. If the TV reports no signal, it is not 24op capable on component. If it shows black and white image, it is capable of 240p and that I should proceed with component mod. When I tested with my Duo, I got something that is not a no signal screen but not a picture. The same port checks fine with my BD player so it is not a broken port. Switching between 16:9 and 4:3 mode did not make a difference. Does it mean a maybe? Or no es bueno?
Did you plug in other RCA cables into the Pb (blue jack) and Pr (red jack) inputs? They must not be connected on the other end, just the TV side. Also, why not use RGB on those systems with an external RGB to Component or HDMI converter? No modding needed unless it doesn't have an RGB output already. EDIT: On second thought that might not have caused that image. I don't know what could've caused it so hopefully someone much more knowledgeable than me knows what that screen means.