RCA Model 1 Converter Prototype

[ohohyodafarted]

You have to wonder how many more working CT-100's would be around if they had stuck to using the existing 16" metal B&W tube shells?
They were much more dependable at holding vacuum than the 15GP22.

I dont think it would have helped. Because all color crt's have to be made in two peices (a front and rear section) so as to allow the placement of phosphor dots and instalation of the shadow mask. Even the early metal prototypes were made in two pieces as can be seen in this photo.

http://www.earlytelevision.org/rca_developmental.html

You will note the rib just rearward of the front lip of the tube. That rib is where the front and rear sections were welded together. This tube suffers from the same leaking weld issues as the 15gp22 and the 21axp22.

Initially we thought the leaks were in the glass to metal bonds, but we have since re-thought the problem and have discovered through using a helium leak detector that it appears the leaks are most often in the weld. That is why we see so many good B&W metal tubes. B&W tubes have no weld, just glass to metal bonds which work very well. Making consistant, vacuum tight welds, is a very hard thing to do when working on light guage metal such as used in these crt's.