#1
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X-Rays from old CRTs
I was chatting with a test engineer recently, and he said something to the effect of "You have to watch those old CRTs, they emit X-Rays". Really? Do I have to wear a lead suit when I watch one now?
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http://nixies.us/ |
#2
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They were designed with shielding.
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#3
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Early monochrome TVs with lower voltage power supplies don't emit harmful amounts of X-Rays. Color and larger screens introduced higher and higher anode voltages, and they became quite effective producers of X rays. This was recognized as a health hazard, and beginning in the late 60s, TVs included a lot of shielding to block the X rays from leaving the set. There will be an X ray shield around the bell of the CRT, and the flyback and high voltage rectifier are fully enclosed. Provided all the shielding is in place, they were tested to produce an amount of X rays which wasn't harmful. A lot of media attention was focused on TVs and X rays around the time when standards for shielding were being introduced.
Another thing to remember is the intensity of x rays decays exponentially with distance, so sitting on your couch there is pretty much no risk with about any old TV. The conclusion I take from learning about this issue, is that the only TVs you really need to be careful about, are those with safety features which have been defeated, or pre 1968 colour or projection sets with a high (>15kV) voltage on the anode of the CRT. For those sets, the idea would be to keep a distance. Also, if a TV loses high voltage regulation, and produces excessive high voltage, it can also produce excessive x rays, so only use TV sets which are in good operating condition. There's many publications which talk about the issue of X rays and TV, and if you didn't find it already, I suggest using the resources at www.americanradiohistory.com to search the various industry publications of the era for articles on the subject. |
#4
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TV repairmen that spent 8 hours a day every day right next to operating sets never were harmed by X-RAYS...there was a big media ignoramus driven TV X-RAY scare in the 60's that was more fear mongering than science, it resulted in better safety in new sets and dummies continuing to spread the media wives tale.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#5
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Was helping a friend clean out an estate garage today, and we pitched two new-in-box "radiation shields" for use on CRT computer monitors. Looked like a hoop that went around back, and probably a screen of some type over the front. I suppose if you spent your life in front of a bank of them, it might get your attention. But likely fear mongering, as Tom remarked...
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Audiokarma |
#6
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If there was ever an X-ray problem as hyped back in the day, all my kids oughta had 6 fingers and two heads.
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#7
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Most of the X-Rays from color sets came from the 6BK4 Regulator tube, some of the early ones could shoot out signifigant amounts, but usually straight down under the set. The amount coming off the front of the CRT is negligible unless you spend all day pressed up against the face of the tube. There is a shit load of Lead in color tubes.
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#8
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This is about what I figured. Thanks for the info.
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http://nixies.us/ |
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