Adding Composite Video Input to my RCA CTC21 Chassis

[Electronic M]

If the entire image is hard to get horizontal lock on check that tube and replace the AFC diodes. If the monochrome has solid lock and good locking range on the control but the color has poor lock may have to adjust the chroma reference osc coil... You'll need a plastic hex alignment tool (count turns so you can get back).
Sometimes poor color lock can be exacerbated by the horizontal lock being poor or the image being locked at an extreme edge such that the burst is not being gated to sync the chroma osc.