Good to hear this is coming along, considering my break from early color 21-fun (till I'm driven indoors by cold) I have nothing new to report.
A video posted by Shang066
https://www.youtube.com/watch?v=caS-GKl19KA highlights the desirability of an RCA CTC16XL and how its easier to diagnose than a Zenith 24NC31, which will requires advanced troubleshooting!~
For my CTC20, a few issues remain including focus taking a few minutes to dial in, sound issue due to PC board connection, it did take a replacement of all the electrolytics to fix the pesky sync issue.