[jpdylon]

If I were to make a rough guess, The main reasons why the chromas make better pictures are as follows.

1. Lower operating, fully regulated B+ voltage. Between heaters and high voltage, tubes generate heat - alot of it. This heat wears out components. When your IF strip is closed up - the RCAs are generating a hotbox for the IF strip - whereas the chromacolor remains cool - making components last longer. I'm sure if you replaced everything in the IF strip and realigned - your video response would sharpen up quite a bit.

2. Full DC restoration. Most of the RCAs of the mid to late 60s had only partial DC restoration. It was less expensive to design and was not as demanding on the high voltage supply. However partial DC restoration does not yield as vivid contrast.

3. The chromacolors have a superior high voltage supply that is fully regulated. The tripler unit also takes a load off of the horizontal output stage by requiring less current of the output stage. The solid state rectifier an regulator are not subject to "sag" like their older tube counterparts. When you crank the brightness or contrast and the full demand of the 25k is needed at high beam current - the solid state HV supply does it! Try full DC restoration and high contrast on a mid to late 60s RCA and it will bloom to black. Even the 4 tube chromacolor hybrids had the solid state power supply - just no DC restoration. Older sets with DC restoration like the CTC-2b and CTC 100 had double shunt regulators in the high voltage supply for much better stability and a brighter picture - but again it was more expensive to make.

4. The color circuitry of the chromacolors uses an IC to process the color. It operates at a low voltage and is less likely to fail. You could make the tube color set work nearly as well with component replacement and alignment - but I don't think it will ever be quite as good. I've tweaked out both my 11 and a CCII and they come close - but the chromacolor II beats it out with slightly better demodulation on top of the video amp DC restoration.

5. The convergence assemblies for the chromacolor II were made at the pinnacle of Delta Gun technology. By the mid 70s manufacturers had pretty much perfected manufacture of the gun assembly and shadow mask, as well as understood what magnetic influences were necessary to achieve that perfect convergence picture. There are some RCA sets of the mid 70s with delta guns that I've seen with near perfect convergence as well. 1966-67 around the time the 22 and 28 were made, was in the early days of mass produced delta gun rectangular CRTs. At that point I think they were more concerned with banging out the high demand rectangular CRTs than perfection. I'm sure more people were still riding on the high of color television considering it was still somewhat pricey.

6. Safety glass! Pull off the safety glass or bonded face of any color set of the 60s and you'll see the glass is heavily smoked. This was to reduce glare on the face of the tube - but severely blocks light! The CCII and other later sets with black matrix tubes eliminated the need for smoked glass as there was less of the possibility of light reflecting off the shadow mask causing glare. Want a brighter picture with better contrast? Just remove the safety glass and you'll get about 10% brighter, but if light hits the tubeface it becomes really difficult to view blacks.

Just my thoughts. Interesting post Chad! Got my brain juices flowing.