Videokarma.org TV - Video - Vintage Television & Radio Forums

- Early Color Television (http://www.videokarma.org/forumdisplay.php?f=36)

- - CT-100 mumetal shield removal (http://www.videokarma.org/showthread.php?t=272266)

Aha! Now I see that the fifth one is +/- I and Q. It was satuated to full red/cyan/green/magenta before.

There was a minor problem shown in these pictures, best seen in the one of
the children bearing leaves and the leftmost B&W intensity step pattern. You
will note that the left half of the screen was a bit reddish. This was clearly
visible with contrast all the way down (which in a CT-100 turns color all the
way down too) and brightness way up. (The background in the Christmas picture
is supposed to be a yellowish off-white.)

It was caused by a modification I made after the first internal arc in the old
CRT. I added 100K resistors in series with each CRT screen grid (G2). These
are used in all the RCA 21AXP22 and 21CYP22 sets to protect against damage
from arcs to or from G2, which is connected to a big fat 80 uF cap.
I did not remove them.

This allowed capacitative pickup from the multi-hundred-volt dynamic focus and
convergence waveforms. It was cured, with no loss to the protective function,
by bypassing the three resistors with 1 kV 1nF ceramic caps.

P.S. .... the children, of course, were back in 1954 wishing for a CT-100,
just like me!

Yesterday I made one more try at doing the settings on my CT-100. Since I have
a carefully calibrated Sony 55 inch LCD TV, I decided to compare them. I have things
arranged so that the output of my NTSC modulator goes back into my OTA antenna
distribution. So I checked that the Sony produced the same color and gamma on both
digital and remodulated NTSC of the same OTA signal. For color they are identical,
and gamma is quite close. Then I went to adjust the CT-100 to be the same.

However ... it already was the same color as the modulated signal! Even the gamma
was very close. The only adjustment needed was a tiny tweek of the blue background,
really tiny. (Both sets had been calibrated for "sunny clear day" color temperature.)

Every color all around the CIE chart was the same. This was never achieved with the old 15GP22.

I also did another test. Since the Sony is LCD, it produces 100% polarized light.
Therefore brightness can be reduced simply by looking through a large sheet of tilted
Polaroid film, and the amount of reduction calculated from the angle, measured by
a protracter. This test says the Sony is about 4.5 times brighter than the CT-100.