Sharp MZ

So I have two MZ-821 now. The first have the usual video outputs : DIN8 + RF + composite. The second has no RF output and no composite as well: the expected composite plug appears to be just a video output for some SHARP monochome monitors.

The one with composite signal: The other without composite signal: Here is what I get trying to get it as a composite: Not so great, right?

I tried to capture the video output signal to see how it is.

First a real composite signal through my first MZ-821 (with composite signal) :
The signal has a color-burst and looks like a composite one.

Now the unknown signal through my second MZ-821 (without composite signal): Now wonder there is no color: no color-burst. There is also an interrupt "MONITOR <-> TV" but I got the same results.

So I guess the only way to get colors is doing so through the RGBI (DIN8).