What is the theory behind low voltage focus CRTs?

[ARC Tech-109]

I notice the same effect on my Panasonic Tau series with the velocity modulation, basically the same effect using a magnetic field to squeeze the beam. It has a horizontal & vertical plane focus and when they're adjusted right I can clearly see the moire from the mask. The problem with this is running in 1080i I get a third beat on the fine details and patterns and have to run the focus out slightly, granted this is a slot matrix but the effects are about the same and it seems like a step back given the limitations of the CRT. This is one reason why I'm not going LCD any time soon, too much emphasis on the fine details at the cost of the big picture. Just my $0.02, half went to taxes.

I do have a 1970 model Astro Sonic with all the bias and drive controls plus the tube focus rectifier that would benefit from this. At some point I will design a betacam component input interface for it using tubes, that will give it something to show.

[zenith2134]

General Electric was still using the focus stakes into the 80s with their PC chassis sets. Which made a stunning picture and not "just okay for a GE".

Some of you may recall when I got my '66 portacolor
years ago and was attempting to obtain better focus from it. No dice, the 11SP22 just had that compromise phosphor pattern you could have shot holes through. Convergence was also an issue even though it
was a small tube.

It was a runner though. Interestingly enough, 20+ years after the tube portacolors, GE came out with an under the counter kitchen set #7-7650; with a Matsushita sourced 5" color inline tube....VERY coarse phosphor pattern too. But this time, (1986-88), it had a focus pot off the flyback in addition to a builtin degausser.

[ChrisW6ATV]

Originally Posted by LukeSimon

When life gives you pigs, you might as well put lipstick on them.

I love this comment! I may find a good place to use it in the future, I hope you do not mind.

I am also in the Bay Area, and there are several early TV-set collectors in this area and adjacent regions. You are right that not a whole lot of older TV sets show up for sale around here, but over time you may get lucky as I have.