COLOR CRT MANUFACTURING in the Mullard Plant

[julianburke]

As you know the color CRT is the heart of a color set. It has many mysteries of how it was made and myself once being involved of their manufacture, would like to amplify this subject. Every manufacturer had their own "trade secrets" of how they made their brand of tubes and I have given talks of CRT manufacture but this is the best film I have seen yet. I once visited a plant to learn techniques for a rebuilding plant I worked at in high school but no pictures were allowed.

If anyone wants to see how color CRT's are made, here is a great piece of British footage of instructional nature. It seems that the Brits made many television instructional films of a highly technical nature for home use! This one was made in the Mullard plant which would be a rare thing for them to do. It also has rare footage of how the delicate shadow mask was "developed" as well as the faceplate which unlocks this mystery! This information was highly proprietary hence this extremely rare footage. ENJOY!

This YouTube is in two parts.

http://www.youtube.com/watch?v=eiKp4...eature=related


They don't show the tubes being placed in their ovens for evacuating as this is the last step in manufacturing. They are evacuated in a 400 degree gas fired oven to expand the atmosphere inside the CRT to help draw a harder vacuum with fewer impurities. Yes, occasionally one will implode in the oven due to a flaw in the glass somewhere and at that moment someone (usually me at my plant) will scurry over to it to shut down the vacuum pump on that tube to prevent further contamination from getting into it, and oil in both mechanical and diffusion pumps would have to be changed. (not a fun job!)

[Duke Nukem]

The BVWS (British Vintage Wireless Society) (blatent plug )have released a number of DVD's of this type of material over the years (including the one referred to on YouTube), having had permission from Philips/Mullard to do so. I know as I authored some of the DVD's.

Fascinating and informative these films certainly are, I don't think anything really proprietary/secret is shown - the general principles are largely the same, its the fine details that would be secret. For example temperature/time/heater drive during activation.

TTFN,
Jon

[andy]

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[Eric H]

He calls the little plates control grid cooling fins but would "cooling fins" really work in an airless environment?

[Tom_Ryan]

Originally Posted by Eric H

He calls the little plates control grid cooling fins but would "cooling fins" really work in an airless environment?

Yes. Eric, in vacuum tubes virtually all anode heating comes from the kinetic energy of electrons striking the anode. The actual resistance of materials in the anode (and other elements in the tube) is very low, and the relatively small amount of heating is dwarfed by electrons impacting the surface of materials in the tube, including the control grid. Those little plates help to dissipate heat given off as infrared radiation, which passes through the vacuum and is absorbed by the glass neck, or envelope, of the tube, ultimately transferring to the surrounding air on the outside.

[John Marinello]

Appears these were evacuated at room temp?

[old_tv_nut]

Originally Posted by John Marinello

Appears these were evacuated at room temp?

No, they proceed into an oven. The film shows only the cart loading area.

[RCAkid]

Really cool to see these videos. It's amazing how much one can learn in less than 20 minutes.

I always wondered how these were really put together and it is enlightening.

[jeyurkon]

After seeing how much labor was involved it makes me wonder how we could have ever afforded a color CRT.

John

[Sandy G]

Tres Kewl ! Learned a lot from these 2...

[old_tv_nut]

This is the first film I've seen that showed all the steps to this degree. Some of the details that you might not think of as proprietary actually could be quite critical, for example the exact tilt and rotation rate of the faceplate while the phosphor is applied. At one time, Sylvania was leading the pack in incremental improvements in tube brightness, and they came up with a particularly thick phosphor slurry that improved brightness. Motorola had no problem duplicating the results, except that first trials resulted in visible swirl marks in the picture, until they also discovered the required tilt, rotation speed, and application volume/rate. At one point, employees were requested to take home two identical receivers and watch them side by side, the only difference being the new process in one tube. We were to observe silently and ask others to compare the sets without any prompting of what the difference might be, to see if swirls were visible to untrained eyes.