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Old 11-24-2017, 01:45 PM
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Update: we have been working on our RCA 21CTC55 receiver. Bottom line we intend to do a third test soon.

Below is what we wrote for our blog.

“We are very excited, proud and pleased with the results Mike and I achieved restoring this RCA 21CT55, a 62 year old television. Credit also to Dave, Kevin, Walter and Bob. I’m not ashamed to say “I like showing it off”.

A comparison test of a 1954/55 RCA 21CT55 and a 1958 RCA CTC-7 Worthington.

A new test to compare the image and color reproduction of the two sets. We wanted to show the differences in the first production 21 inch color set with wide-band, six IF stages and superior demodulation. The 21AXP22 also has the wide color gamut phosphors. The CTC-7 came four years later and considered to be the first truly reliable RCA color television. This CTC-7 has a rebuilt 21CYP22A. It must be said that both CRT’s tested “Good” at cut off, but the 21CYP22A tested very strong and the 21AXP22 tested weaker. The red gun in the 21AXP22 is the weakest.

We found a good quality, low loss signal splitter in my “pile of stuff” and hooked up both sets, so we can photograph both simultaneously. Experience with the camera I’m using (not the best) shows that ambient light in the room will influence the true color reproduction subject to the cameras limitations, because the camera is reading ALL the light in the room. Because collectors like to see the cabinet as well as the images, we can limit the ambient light interference by dimming the light source just enough to show the cabinet highlights with the majority of the lit screen composed in the viewfinder.

In photographing both CRT screens at the same time in the same frame, we must move further back and the ambient light will definitely influence the results. We must eliminate the light and photograph in near total darkness.

Both sets were adjusted and set up to RCA procedure recommendations. The two sets were first adjusted by eye individually for the best combination of color saturation, hue, brightness and contrast. No test instruments. (the eye can be the best test instrument). This is subjective, what I like, you may not like. My eyes have been “trained” to prefer ISF calibrated color starting in the 1990’s. I don’t claim to be an expert. ISF color calibration is scientific and quantitative and not subjective.

We used the Gentlemen Prefer Blondes DVD. It is known for great quality, three strip Technicolor.

We powered up both sets and let them settle in for 30 minutes and tuned off the lights. This time we had to take an “average” exposure. Unlike a good DSLR, my camera only has one focus and aperture point to set. We set the camera focus and exposure point in a darker area equal distance between the two lit screens. This created under exposed dark screen images, so we compensated by increasing the exposure with the camera to match what my eyes were seeing.

Both sets have fans added to the flyback cage to help cooling. The fans can be switched off. Both sets are protected by a Furman Discrete Symmetrical Power Model IT Reference 7.

After this test was completed, it occurred to me that we should have calibrated both sets using the SMPTE color bars from the Joe Kane Video Essentials DVD and blue filter. Maybe next time when we get a good DSLR.

Update notes and analysis: During the test which took over an hour, the 21CT55 screen images enlarged and increased in brightness. The CTC-7 stayed constant. The CTC-7 came up about 10 seconds later. In these shots and live, to my eyes, the 21CT55 consistently resolves more detail then the CTC-7. The geometry is adjusted better in the 21CT55. Look at slides 1 and 9. Blue shifted to violet. The CTC-7 could not register the bright spotlight scenes properly during the dance sequences. (Slide 26) The facial tones shifted to green and the dress shifted to violet. This could be adjusted, but we wanted to leave all setting the same from start to finish. The CTC-7 images are slightly brighter but is expected in the newer 21CYP22A. You can also see the differences in the red phosphors and the 21CT55 shows better details in the shadows and in bright areas. The results of this test show that we need to adjust the 21CT55 “warmer”, less blue and the CTC-7 should be “cooler” more blue.

Onward we go. Maybe my wife will buy me a nice DSLR for Christmas? Hint …..��❤️ The Tournament of Roses parade is coming soon. We intend to do a third test prior to the parade live telecast via rooftop antenna converted to analog, after calibration with the SMPTE color bars and blue filter.

Back on that historic day, January 1, 1954 when RCA and NBC broadcast the first coast to coast color program of the parade, folks in my hometown of Milwaukee could not view that color broadcast unless they were invited to one of the four private demonstrations or the one public demonstration at a television dealership. The color televisions used for those demonstrations were prototype Model 5 receivers.

The following year parade telecast on January 1, 1955, could be viewed on Admiral, Westinghouse, RCA, and other color sets, including a 1954/55 RCA 21CT55. Next years telcast (January 1, 2018) will be our first opportunity to recreate that historic event, but this time we will see the technology differences made possible with modern color cameras and studio chain equipment. Let’s do this.”

Once again, we can’t give you a direct link to the slide show. The slideshow and future slideshow can be viewed at the bottom page of this link:

https://visions4netjournal.com/vinta...tv-page-two-2/
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