What is the theory behind low voltage focus CRTs?

[LukeSimon]

Originally Posted by Electronic M

You may be trying to put lipstick on a pig going to those lengths for a portacolor...the first gen portacolor sets had a phosphor dot pitch too coarse for good NTSC.
The first gen portacolor CRTs instead of doing the right thing and making a new shadow mask with enough holes for the right number of phosphor triads to achieve full NTSC resolution, GE got lazy and simply cut the center 10" diagonal square out of a 21FBP22 roundy shadow mask and called it a day with something like 1/4 of the the triads it should have had...

Later with the IIRC 11WP22 in the second chassis generation portacolor they actually bothered to make a new shadow mask with a finer more appropriate dot pitch (I'd like to find one of those one day).

I am sure you are right, that is, moire effect will become very bad due to the bad dot pitch. My main goal is to learn new things and to see how far I can push things. I find CRT technology to be fascinating, and after getting into 1960s TVs… I am finding that non-solid state TVs are even more fascinating.

This is my first tube color TV. Sadly, in my area, vacuum tube TVs are very rare. This portacolor was a 6 hour drive round trip. A high end color tube TV like an early 1960s RCA… I may never get my hands on one. When life gives you pigs, you might as well put lipstick on them.

I am always accepting better color tube TVs, if anyone wants to donate one to me.