6 ms·

When Televisions Emitted X-Rays

70 points by Hooke 8y ago

tlb 8y ago
"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 8y ago
  Ok, we've edited the title accordingly. Thanks!
peter303 8y ago
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 8y ago
  Believe me, many parents love to bring up phones as a “source of radiation” to get their children to stop using them.
  - toss1 8y ago
    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...
- Retric 8y ago
  High voltage lines have been demonstrated to harm plant life. With a few different proposed methods of action, IMO the most interesting is extracting pollution from the air the same way ionic air purifier‘s work. This will sometimes show up as significantly lower plant growth under them which reasonably makes people nervous.
  - dekhn 8y ago
    Can you provide links to high quality studies that would convince a skeptic of your claim? I am unable to find studies demonstrating strong causal relationship between high voltage lines and reduced health.
    - Retric 8y ago
      'plant life' not human health. I am not sure what you would consider high quality, but here is the method of action in a very neutral setting: 'The mechanism of pollution of insulators is governed mainly by: the pull of gravity, wind forces, electrostatic forces on neutral and charged particles, aerodynamic and surface factors of the insulators, humidity, particle size, and chemical composition' https://www.tandfonline.com/doi/pdf/10.1080/00022470.1979.10470923 https://www.tandfonline.com/doi/pdf/10.1080/00022470.1979.10...
      - dekhn 8y ago
        wrong link? article is about preventing corrosion on transmission lines. There is nothing about plant life here.
- ataturk 8y ago
  If either were really a problem we would definitely all be ill by now.
- jjoonathan 8y ago
  Dude, your cell phone is a couple of watts of non-ionizing RF at approximately 0 duty cycle. Under what standard does that count as high intensity? The latest "mice in a microwave" study I've seen shows a need to bathe mice in the human scale equivalent of 200W, 100% duty cycle RF before they see a measurable effect and even then there are strong reasons to supect p-hacking (e.g. effect is barely significant, they don't control heat input, effect vanishes in female mice, etc). The hypothesis "RF causes cancer" is easy to test (it's easy to crank up the RF dose) and, if correct, would be extremely rewarding for the researchers involved. It has, unsurprisingly, been extensively investigated -- so if it's true, why does every paper that I read with a positive result seem to have cheated in order to obtain it?
- SigmundA 8y ago
  I find it strange people worry about a 300 milliwatt gigahertz radiation source while walking around outside under a nuclear fireball emitting terahertz radiation at 1000 watt per square meter that is known to cause cancer.
mnw21cam 8y ago
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 8y ago
  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.
jshprentz 8y ago
Radiation King TV on the Simpsons (12-second clip): https://www.youtube.com/watch?v=2ScUjHWUL34 https://www.youtube.com/watch?v=2ScUjHWUL34
jtr_47 8y ago
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!
dekhn 8y ago
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.
Jeema101 8y ago
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
- EADGBE 8y ago
  Cool resource. All this discussion made me really question my tube amp (guitar) collection, though.
  - Jeema101 8y ago
    Nothing to worry about - the voltages aren't high enough in a tube amplifier. X-rays only come into play when dealing with tens of thousands of volts.
  - justtopost 8y ago
    I will protect your from the dangerous tube-rays. Fedex me your amps, and I will send you nice, safe, solid state ones.
    - EADGBE 8y ago
      Thank God!
ungzd 8y ago
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-Radiation/s?ie=UTF8&page=1&rh=n%3A15782001%2Cp_n_feature_keywords_browse-bin%3A5502697011 https://www.amazon.com/Anti-Glare-Privacy-Filters-Anti-Radia... 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.
DoctorOetker 8y ago
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?

70 points by Hooke 8y ago

tlb 8y ago

"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 8y ago
Ok, we've edited the title accordingly. Thanks!

peter303 8y ago

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 8y ago
Believe me, many parents love to bring up phones as a “source of radiation” to get their children to stop using them.
- toss1 8y ago
  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...
Retric 8y ago
High voltage lines have been demonstrated to harm plant life. With a few different proposed methods of action, IMO the most interesting is extracting pollution from the air the same way ionic air purifier‘s work. This will sometimes show up as significantly lower plant growth under them which reasonably makes people nervous.
- dekhn 8y ago
  Can you provide links to high quality studies that would convince a skeptic of your claim? I am unable to find studies demonstrating strong causal relationship between high voltage lines and reduced health.
  - Retric 8y ago
    'plant life' not human health. I am not sure what you would consider high quality, but here is the method of action in a very neutral setting: 'The mechanism of pollution of insulators is governed mainly by: the pull of gravity, wind forces, electrostatic forces on neutral and charged particles, aerodynamic and surface factors of the insulators, humidity, particle size, and chemical composition' https://www.tandfonline.com/doi/pdf/10.1080/00022470.1979.10470923 https://www.tandfonline.com/doi/pdf/10.1080/00022470.1979.10...
    - dekhn 8y ago
      wrong link? article is about preventing corrosion on transmission lines. There is nothing about plant life here.
ataturk 8y ago
If either were really a problem we would definitely all be ill by now.
jjoonathan 8y ago
Dude, your cell phone is a couple of watts of non-ionizing RF at approximately 0 duty cycle. Under what standard does that count as high intensity? The latest "mice in a microwave" study I've seen shows a need to bathe mice in the human scale equivalent of 200W, 100% duty cycle RF before they see a measurable effect and even then there are strong reasons to supect p-hacking (e.g. effect is barely significant, they don't control heat input, effect vanishes in female mice, etc). The hypothesis "RF causes cancer" is easy to test (it's easy to crank up the RF dose) and, if correct, would be extremely rewarding for the researchers involved. It has, unsurprisingly, been extensively investigated -- so if it's true, why does every paper that I read with a positive result seem to have cheated in order to obtain it?
SigmundA 8y ago
I find it strange people worry about a 300 milliwatt gigahertz radiation source while walking around outside under a nuclear fireball emitting terahertz radiation at 1000 watt per square meter that is known to cause cancer.

mnw21cam 8y ago

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 8y ago
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.

jshprentz 8y ago

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

jtr_47 8y ago

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!

dekhn 8y ago

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.

Jeema101 8y ago

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

EADGBE 8y ago
Cool resource. All this discussion made me really question my tube amp (guitar) collection, though.
- Jeema101 8y ago
  Nothing to worry about - the voltages aren't high enough in a tube amplifier. X-rays only come into play when dealing with tens of thousands of volts.
- justtopost 8y ago
  I will protect your from the dangerous tube-rays. Fedex me your amps, and I will send you nice, safe, solid state ones.
  - EADGBE 8y ago
    Thank God!

ungzd 8y ago

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

DoctorOetker 8y ago

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?