Restoring a RCA 21CT55

[etype2]

Ben,

Yes, that bothers me. On all the screenshots so far, women's lipstick just will not display well. The red is there though. You see it in her hair. I have a screenshot of JoAnne Worley from the Laugh In show in 1969 and her bright red feather boa displays with good red, but it doesn't pop.

On the pattern generator, all three colors look good. More adjusrtment with the color gain controls? Mike said the all three guns tested strong, just not new.

[dtvmcdonald]

Originally Posted by etype2

Ben,

Yes, that bothers me. On all the screenshots so far, women's lipstick just will not display well. The red is there though. You see it in her hair. I have a screenshot of JoAnne Worley from the Laugh In show in 1969 and her bright red feather boa displays with good red, but it doesn't pop.

On the pattern generator, all three colors look good. More adjusrtment with the color gain controls? Mike said the all three guns tested strong, just not new.

Don't expect lipstick or other really bright red things to look right in
real scenes.

Several things to check:

1) is your modulator being overdriven? That will do it. Step 2) checks this.

2) check B&W step patterns on all three guns ... be sure the red
one is not seriously overdriven. This will also check 1). I suggest lots
(like 30) of steps.

3) check the fine tuning and IF response with a full-screen horizontal
chirp test (e.g. Digital Video Essentials), with the color control all the way down.
There should not be a dark area where the chirp goes into
the color region (starting at say 2.2 MHz) . If adjustment of fine tuning does not get
a sharp picture (i.e. down more more than 25% at 3 MHz) , good amount of color
(on a color picture), and lack of the dark area, you probably need a full RF-IF alignment.

4) check the setting of the R-Y drive pot by examining the
R-G-B CRT grid waveforms with a scope, at low contrast settings, using
normal color bars. The should show all the bars at only two levels.
Adjust the R-Y pot, color level, and hue until its as good as possible on all three.

5) check adjust contrast and brightness for proper bar appearance
being sure that the red gun is just barely clipping.

6) recheck the gray step pattern to be sure it is uniform color. If
not, readjust screen and video gains. Be sure to check the red screen pot ...
all the way CW may not be best, run through the whole range. Then recheck 5).

I just did this yesterday on my CT-100 and found 6 to be a problem.
The gamma is too high on these CRTs and you may be unable to get
good bright reds and good scene visibility in dark scenes at the same time.

4) can't be reliably done by eye ... you may be setting with too much red clip.
You need a scope.

Repeat until you understand what is going on.

Doug McDonald