
When Televisions Emitted X-Rays - Hooke
https://www.theatlantic.com/technology/archive/2018/09/when-televisions-were-radioactive/570916/?single_page=true
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mnw21cam
Back in the late 90s, I saw a demo of a 3D television in a university, where
they had a row of ten or so cameras, and had developed a television with an
LCD shutter in front of it that allowed it to project ten images, so you would
see a different image in each eye, and you could move your head around the
television to see around the objects portrayed on it. It was nifty technology
back then.

The disadvantage was that the television had to draw its images ten times
faster than a normal screen, in order to project each image in turn. In order
to do this with an acceptable brightness, the electron acceleration voltage
had to be quite high, and the tube produced an appreciable dosage of X-rays.
To cope with this, the cathode-ray tube was actually pointing at the floor,
with a mirror underneath it so you could see the image. At the bottom of the
unit was a chunky block of concrete to absorb the X-rays and protect the
people working on the floor below.

~~~
spongeb00b
I can remember something similar about the same time being shown on BBCs
Tomorrows World. Back then the idea of 3D TV was that you could change the
perspective of what you were seeing by moving your head. From memory I think
the screen had some kind of honeycomb pattern over it which was to do with
their implementation of the different perspectives.

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tlb
"Radioactive" is the wrong word, as there's no nuclear decay involved. The
concern was X-rays. A CRT looks a lot like an X-ray tube, where you accelerate
electrons through 10^4 volts and smash them into a metal target, producing
photons with 10^4 eV energy. These X-ray photons penetrate the body and cause
tissue damage over time.

~~~
dang
Ok, we've edited the title accordingly. Thanks!

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Jeema101
The main source of X rays in old tube televisions wasn't actually the CRT as
far as I know - it was the high voltage rectifier and shunt regulator tubes.
Later versions of some of these tubes apparently used leaded glass
specifically to mitigate this.

This guy I watch on YouTube who repairs old electronics explains it here in
one of his repair videos:

[https://www.youtube.com/watch?v=mdcA93xJh2g#t=5m40s](https://www.youtube.com/watch?v=mdcA93xJh2g#t=5m40s)

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EADGBE
Cool resource.

All this discussion made me really question my tube amp (guitar) collection,
though.

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justtopost
I will protect your from the dangerous tube-rays. Fedex me your amps, and I
will send you nice, safe, solid state ones.

~~~
EADGBE
Thank God!

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jshprentz
Radiation King TV on the Simpsons (12-second clip):
[https://www.youtube.com/watch?v=2ScUjHWUL34](https://www.youtube.com/watch?v=2ScUjHWUL34)

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jtr_47
In late 70's and 80's we had a TV (x-ray gun) - an RCA that sat on the floor
of our living room. Our carpet in the living room, which was never shampooed,
in front of the TV turned much darker than the rest of the carpet in the
living room over time. This was noticeable when the original RCA died and we
got another in the late 80's.

I used to sit close to the TV sometimes. I enjoyed the static & anti-gravity
of the screen when the TV was turned on. It was cool looking at dust particles
falling into the screen :)

Those were the days!

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ungzd
Computer monitor filters were very popular in post-USSR until 2000s, and whole
paranoia about CRT radiation continued until CRT were fully replaced by LCDs.

And seems that such filters are still produced, and sometimes are marketed to
be used even on LCDs!

\-
[http://www.visioncarefilters.com/products_3M.html](http://www.visioncarefilters.com/products_3M.html)

\- [https://www.amazon.com/Anti-Glare-Privacy-Filters-Anti-
Radia...](https://www.amazon.com/Anti-Glare-Privacy-Filters-Anti-
Radiation/s?ie=UTF8&page=1&rh=n%3A15782001%2Cp_n_feature_keywords_browse-
bin%3A5502697011)

One of "folk" ways to reduce radiation was to put a pot with cactus near
monitor, which "absorb" radiation, despite complete absurdity, it was quite
popular in Russia.

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dekhn
As a kid in the late 70s I recall people telling me if I sat too close to the
TV I'd catch a cancer.

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DoctorOetker
Does anyone know what the typical X-ray spectra and intensities were for
television CRT's from 1995-2005 period?

There is no links or mention of actual levels in SI units etc...

EDIT: some extra comments:

1) The article mentions that upon closer inspection the X-rays were emitted
mostly below and above and to the sides of the television tube.

2) This makes perfect sense for Brehmsstralung ("braking radiation") since
these are emitted orthogonally to the cathode rays.

3) The article mentions also that in this plane, most x-rays were directed to
the floor. I see no basis in physics to support this. This does seem like
soothing the public (few people are positioned below a television, while
people might regularly place themselves to the side depending, say the dinner
table next to the television, in a family where a parent arrives home later
than the kids have eaten etc...). If anyone can explain from physics
prinicples why Brehmstrahlung would preferentially be emitted to the floor I
would love to hear it and correct my views.

4) It is often repeated that the X-rays came not from the picture tube, but
from a rectifier tube. How do the voltage and current across this tube compare
to the one through the picture tube? How do you commensurate this explanation
with the observation that X-rays are detected in the plane of the picture tube
(orthogonal to cathode rays as expected)? Wouldn't these rectifier tubes be
positioned in different orientations depending on make and model? Why was the
bulk of the radiation detected in the same plane as the picture tube plane?

5) I recently (~2 years ago) moved to the appartment I currently live in. It's
in a city block so from the balcony on the rear side I can see the rear side
of all the brick buildings on the other side of the same city block, about 80m
away, so they are on a street parallel to mine. The contract stated we weren't
allowed to have CRT televisions in our appartment (which I thought was weird
or strange, but didn't care about since I had no CRT tube). A while later I
walked around the block, and while walking through the street parallel to
mine, I noticed a private radiologist on the other side of that street, then
the very next neighbour _also_ housed a radiologist, a competitor! and a few
houses on another one. So a couple of radiologists are clustered together. It
is clear that with the historically larger radiation doses in radiology
(before the much more sensitive modern scintillators and phosphors became
available), that this was an organized pattern by authorities (to minimize
radiation to the public) and/or the radiologists (to minimize noise from
picture tubes decreasing contrast on their images). From inside my apartment
to the radiologists there are 2 brick buildings: half a building from inside
my appartment to the back yards. Then a full building of street house to the
street of the radiologists, then another half building into the radiologist.
The total distance is about 100m = 80m + 20m (it's a wide street). So there is
probably a radius of 100m where CRT tubes are banned.

I am asking about the typical intensity spectrum of X-rays, since it would be
cool to use a CRT tube as a flying spot scanner, with a single detector
camera. Making X-rays of PCB's hands etc. Who cares if the level is low, it'll
just take time. And if it's _that_ low, why ban CRT's within 100m radius and 2
full brick buildings in between?

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peter303
I have thought it irironic that some people worry about high voltage
transmission lines in their, yet carry a high intensity electromagnetic
radiation source next to their privates most of the day- cellphone in their
pants pocket. Neither situation has been proven dangerous in a scientific
study. But the former is occasionally protested by scientifically ignorant and
later overlooked by feeelings of convenience.

~~~
saagarjha
Believe me, many parents love to bring up phones as a “source of radiation” to
get their children to stop using them.

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toss1
Reminds me of a story a friend told me from the days of working IT supporting
10BaseT coaxial Ethernet cabling, where if you broke the line at any one
T-connector, the whole set of nodes on that cable went offline. One secretary
was annoyed by something about the line under her desk and kept disconnecting
it despite requests.

He finally came up with the idea to explain her that the cable end "leaked
radiation" when unplugged -- technically true, just not at levels relevant to
human health. From that day forward, no more issues...

