CT-100 mumetal shield removal
 

I've obtained a good 15GP22 for my CT-100.

I'm trying to get the mumetal shield of the old, gassy, 15GP22. Its stuck.
One can see some sort of spacers doing the sticking. What are they,
and how does one loosen them? Presumably some sort of solvent?
I don't want to just start trying at random.

Other folks surely have had this problem before.

Trying to slip some sort of tool in looks hopelessly dangerous.


Doug McDonald

I will leave it for others to respond to your question. I’ll just say congratulations on finding a good 15GP22.

Not sure if the Westinghouse setup is the same, but on that one it really is only a few rubber spacers around the small end on the inside of the mumetal shield. They seemed to be only stuck due to age and not any kind of adhesive. Mine came off with only a small amount of force. The CRT and shield seem to be a pair since they were both marked with the same handwritten four digit number.

Piano wire can be used to cut the spacers, then clean off the gummy goo after the parts are separated.
Congratulations on your 15GP22 find.

jr

These is no glue between the rubber and the glass. There may be between rubber and the mumetal.

In any case three applications of denatured alcohol with 15 minuites
between them freed the sticky rubber pieces up.

Getting the bezel properly straight took four tries.

The tube works fine. I have merely passable purity so far. The static
convergence was far out. With no magnets I've got it a bit better.
Maybe the magnets will do it. One of my magnets was originally bad.
I never found a replacement, so I'm using a steel threaded rod with
a piece of Alnico glued to the outer end.

Examination of the corpse was interesting. It does not have all-white getters.
What getters there are are nice and black except for a very faint 1/4 inch
white halo. But two of them have separated from the glass and are in pieces,
sort of frilly looking. Its possible a piece fell between two electrodes and caused the fatal arc.

Off to dinner and to relax my back.

http://www.videokarma.org/attachment...1&d=1574039391

Congratulations on finding a replacement CRT. Hopefully we'll get to see it running with the Sony monitor 'heresy' removed in the near future.

Its running nicely, except a bit of purity problem in the lower right corner.
Note: I was careful not to turn either the hue or color level control from where
they were for the Sony. Colors remained correct when gray scale was set right.

At least at the brightness I was running it, the gray scale is gray, and Dorothy's
white dress is actually white. The yellow brick road is not yellow-green.

Test pictures. These were fromn jpgs and the Wizard, all on the same Sony player.
No adjustments were made to the settings except for the convergence patter, which had the color turned off.


Edit: pictures removed for better ones, see later post

Edit: pictures removed for better ones, see later post

Edit: pictures removed for better ones, see later post

Thank you for posting these photos. I always wanted to see your avatar full screen. Very nice. The wreath is stunning.

:thmbsp:

I'm really awed by the color on these, not to mention the convergence. The color level seems just a tad high to me on my monitor, but that may just be a preference rather than a real inaccuracy. The colors are so well balanced, you can get away with that extra "pop" that really says "Technicolor."

The color level edit: WAS much too high. In actual watching I turn it down.

These pictures were made using a color level set according to
standard color bar patterns. There is a color bar in one, but not with the
"adjacent" bars for setting. I made my own ones of those, and they argre
perfectly with those for the old Digital Video Essentials DVD I also used.
My own set has provision for matching red and green as well as the
blue of the DVE set. Blue and red match perfectly. Green matches as well as
expected from the imperfections in both the green phosphor and the green filter.

Two ideas why it in fact is too saturated: One: there is something wrong
with either the DVD player or the modulator. My OTA digibox also makes
equally too-saturated colors. Two: its the imperfect DC restoration and/or
lack of DC coupling of the I and Q signals. Turning down the color gain has
no effect on the hues.

I did it this way because the last time I posted pictures I got flamed
by doing the matching visually.

Edit: the problem was that I set the color level with the fine tuning set
improperly and did the pictures with it set properly. This increased the
color level.

It's interesting that the saturation is high to your eye, and not just an artifact of the camera, web posting, and my monitor.

I found out what was wrong! The color level was set with the fine tuning wrong,
and the pictures taken with it right! All pictures will be replaced with good ones.

http://www.videokarma.org/attachment...1&d=1574373216

http://www.videokarma.org/attachment...1&d=1574373216

http://www.videokarma.org/attachment...1&d=1574373216

http://www.videokarma.org/attachment...1&d=1574373216

http://www.videokarma.org/attachment...1&d=1574373216

more next

pictures from my test collection

http://www.videokarma.org/attachment...1&d=1574373433

http://www.videokarma.org/attachment...1&d=1574373433

http://www.videokarma.org/attachment...1&d=1574373433

http://www.videokarma.org/attachment...1&d=1574373433

another test pattern from my collection: top is +- I and +/- Q

http://www.videokarma.org/attachment...1&d=1574373433

more next

Test patterns from Digital Video Essentials (DVD)
http://www.videokarma.org/attachment...1&d=1574373718

http://www.videokarma.org/attachment...1&d=1574373718

http://www.videokarma.org/attachment...1&d=1574373718

http://www.videokarma.org/attachment...1&d=1574373718

http://www.videokarma.org/attachment...1&d=1574373718

http://www.videokarma.org/attachment...1&d=1574373718

next, the Wizard

http://www.videokarma.org/attachment...1&d=1574373812

http://www.videokarma.org/attachment...1&d=1574373812

http://www.videokarma.org/attachment...1&d=1574373812

http://www.videokarma.org/attachment...1&d=1574373812

http://www.videokarma.org/attachment...1&d=1574373812

Finally, next, the classic Dorothy and the Green Gateman

http://www.videokarma.org/attachment...1&d=1574373958

http://www.videokarma.org/attachment...1&d=1574373958

These really are what the TV looks like.

Happy viewing

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.