Rca ctc-5

[old_tv_nut]

Originally Posted by DaveWM

Yes I am using the gated rainbow pattern. The petals are roughly circular now, but not very pretty (somewhat misshapen pointy, sickle shaped), so I am sure more work could be done, but I am not sure if its a fault of the demodultor or the chroma signal coming from the video detector or maybe just the design. I plan do do an IF and Chroma sweep alingment later with a BK 415.

It may be fun to play with some of the chroma tubes just to see the effect.

it's hard to say exactly what shape the petals should have. Remember that the signal that's being gated is changing phase across the width of each bar, so even if phase response of the chroma is perfect, the trace will go outward from the center and back to the center while changing phase at a rate determined by both the varying phase and the final demodulated chroma bandwidth. Sickle shape is an indication of some phase distortion (rising waveform is different from falling), but this can be affected by fine tuning, adjustment of the sound trap(s), etc. and can be very hard to get perfect. On the other hand, if it's very bad, it will show up as edge discoloration on strongly colored objects.

If you really want to look for distortions, you need regular color bars, which have the same phase across the whole bar. Then you can make out things like the green-magenta transition not going directly across the gray center point, or other transitions not going straight between bars.