Delta Gun Hype/understanding

[trinescope]

Originally Posted by Yamamaya42

Since this thread is about the delta-gun types, there is something that I have always wondered, which was / is the better CRT from a technical / longevity standpoint?
The roundies or the rectangular types?
Granted, you lose a small % of the pic with the roundies, but I don't even think it was really noticed much in it's day.

I'm pretty sure the round CRT shape with the spherical faceplate was used because it has lesser demands on the electronics and the CRT hardware for purity, convergence, and pincushion distortion. When Motorola started making sets with the first modern rectangular tube, the 23EGP22, they had to include extra circuitry for pincushion correction. I'm sure there were changes to the convergence circuits as well since this CRT had a flatter faceplate than the 21" round tubes.

As far as longevity goes, that's more a matter of materials, manufacturing, and end usage by the customer than the shape of the CRT. I would say that on average the later CRTs should hold up better since they had more efficient phosphors and therefore didn't need to run the electron guns as hard.

[old_tv_nut]

Originally Posted by trinescope

... When Motorola started making sets with the first modern rectangular tube, the 23EGP22, they had to include extra circuitry for pincushion correction. I'm sure there were changes to the convergence circuits as well since this CRT had a flatter faceplate than the 21" round tubes...

Correct. Rectangular sets required at least third harmonic horizontal-rate dynamic waveforms in addition to the sawtooth and parabola of the roundies. This adjusted the convergence midway between screen center and the left and right edges.