First Color CRT Sizes (before truth in advertising)

[old_tv_nut]

Originally Posted by trinescope

Looking through the Buyers Guide, the 23" (or 274 square inch) screen size is the infamous 23EGP22. It was based on an existing "23 inch" monochrome tube and has a different overall screen shape than the RCA designed rectangular color CRTs. The aspect ratio of RCAs tubes was more like 5:4 instead of the standard 4:3 associated with NTSC, they also had a bit more curvature at the edges compared to the 23EGP22.

The 1970 25V and 19V types were different from the earlier types, they had a true 4:3 aspect ratio, sharper corners, and a flatter faceplate.

The narrower aspect ratio, cropping the left and right a bit, allowed longer horizontal retrace time, which reduces the peak pulse amplitude in the horizontal output. Not a terribly crucial thing for tube or hybrid sets, but very helpful in designing transistor horizontal outputs when the industry was just barely capable of making transistors with the required breakdown voltage.