How to get tube type RCA to look as good as Zenith Chromacolor 2?

[Chad Hauris]

Recently I have been working on a 1967 RCA CTC-28. It has a new replacement Hi-Lite picture tube put in in 1976 which tests very good on a tester. I have put in all new electrolytic capacitors and rectifier diodes and checked power supply voltages, measured HV and regulator current and horizontal output current and it all looks good.

I have a pretty decent color picture on it but it's not nearly as good in my opinion as the picture on the 1979 Zenith Chromacolor 2 we have in the living room using a very similar 23" delta gun picture tube.

On the RCA the contrast doesn't seem as good (picture can seem washed out) and it seems almost impossible to get perfect convergence. On the Zenith the convergence and linearity are perfect all around the screen...I never thought a delta gun tube could have such good convergence.

I have worked with RCA tube type color sets for around 20 years now and have almost always had problems getting a really vivid picture with good contrast and getting really good convergence. I'm wondering if it may be still be due to weak tubes somewhere or bad maroon capacitors?

I only have one RCA tube type set which has produced a picture that measures up to the Zenith and that is a portable CTC-22 which spent its life in an air conditioned office and probably wasn't used much. I know the console RCA's can produce a better picture than I've seen on most of them but don't think I've found the secret yet to doing it!