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Did I destroy my friend's TV with a magnet? (2022)

fleet.org.au

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Re: Did I destroy my friend's TV with a magnet? (2022)

#11

Post by cardiffspaceman »

degauss wrote: post #7
db48x wrote: post #5

Earlier quoted context omitted.

Correct, the field of the Earth is weak and won’t mess up the image on the TV.

Incorrect. The earth's magnetic field definitely affects Cathode Ray Tubes and many other things. High end CRT computer monitors came with a built in degaussing system and some had controls for aligning the R,G & B electron beams. https://en.wikipedia.org/wiki/Degaussing https://hackaday.com/2016/05/25/wtf-is-degaussing/ From personal experience, I took a 20" Sony Trinitron from Los Angeles to New Zealand in the mid…

I used to move 20-inch CRTs around in the office and have to degauss them. But stationary ones also needed this and the built-in coil was great.

Re: Did I destroy my friend's TV with a magnet? (2022)

#12

Post by ksaj »

kamilner wrote: post #2

There's a throwaway comment in here about the earth's magnetic field affecting CRTs and turning the TV upside down, is that actually true? I would have thought the earth's magnetic field would be incredibly weak in comparison to the deflecting coils.

I just sent an email to my old high school buddy. I'm sure this is incorrect, and I've asked him for his remembrance of something we did on a lark.

One night David Letterman did an episode where throughout the show, the camera(s) did a full 360 degree revolution.

When the show was half-way through, it was of course, upside down. So we turned the television upside down.

I personally don't remember anything unusual about the way the show appeared, other than that the TV was upside down, and then on its side for a few minutes at the 45 minute mark.

If he responds within a reasonable time, I'll follow up to mention if he remembers this the same way I do.

Re: Did I destroy my friend's TV with a magnet? (2022)

#13

Post by ksaj »

degauss wrote: post #7
db48x wrote: post #5

Earlier quoted context omitted.

Correct, the field of the Earth is weak and won’t mess up the image on the TV.

Incorrect. The earth's magnetic field definitely affects Cathode Ray Tubes and many other things. High end CRT computer monitors came with a built in degaussing system and some had controls for aligning the R,G & B electron beams. https://en.wikipedia.org/wiki/Degaussing https://hackaday.com/2016/05/25/wtf-is-degaussing/ From personal experience, I took a 20" Sony Trinitron from Los Angeles to New Zealand in the mid…

To me, this sounds a lot like the directional flow of toilets flushing. I'd have to see this as an actual experiment before I can be convinced of what the webopedia page is claiming.

Check out my previous comment on the time a friend and I watch his TV upside down. There was zero difference that I remember.

Consider where most of the monitors are shipped from. Did they send "southern hemisphere" specific televisions and crt monitors? And what happens at the equator?

Could your monitor have been fritzed on the flight? Did it work normally when you brought it back?

This would actually be a fantastic YouTube video, whether it debunks or proves the claim being equally interesting.

Re: Did I destroy my friend's TV with a magnet? (2022)

#14

Post by ksaj »

cardiffspaceman wrote: post #11
degauss wrote: post #7

Earlier quoted context omitted.

Incorrect. The earth's magnetic field definitely affects Cathode Ray Tubes and many other things. High end CRT computer monitors came with a built in degaussing system and some had controls for aligning the R,G & B electron beams. https://en.wikipedia.org/wiki/Degaussing https://hackaday.com/2016/05/25/wtf-is-degaussing/ From personal experience, I took a 20" Sony Trinitron from Los Angeles to New Zealand in the mid…

I used to move 20-inch CRTs around in the office and have to degauss them. But stationary ones also needed this and the built-in coil was great.

I'm more inclined to blame that on the buzzy neon tube lights overhead, and the computers sitting under them.

Re: Did I destroy my friend's TV with a magnet? (2022)

#15

Post by ksaj »

lukev wrote: post #9
joezydeco wrote: post #6

Earlier quoted context omitted.

And can be repaired, most of the time, with a degaussing coil. https://youtu.be/3pVLizAHby4 There was a time with some of these larger TVs and monitors where a coil was built into the frame and would energize briefly on power up, or with the push of a button on the control panel.

Oh yes, I well remember the "degauss" button on CRT monitors. We had one where it was basically a mini EMP and would make the images on nearby monitors quiver as well. Fun times. I know a magnetic field was being retained somewhere , just wasn't sure which component it was.

Everybody loved the degaussing sound and visuals. Young people don't know what they're missing.

Re: Did I destroy my friend's TV with a magnet? (2022)

#16

Post by duskwuff »

db48x wrote: post #4
lukev wrote: post #3

Is it just me, or does the article not actually answer the question in the title? It explains the components well, and how a magnet distorts the image, but does not describe which component is capable of being permanently altered by an external magnetic field. Is it the phosphor coating? The deflecting coils? Some sort of static field in the glass?

A magnet will bend the electron beams, but that isn’t permanent. A permanent color change made by a magnet only happens by imposing a magnetic field on a metallic component of the monitor, so that the beam is always deflected by it. One component not shown in that diagram is the shadow mask, which divides the screen into discrete dots to be activated by the electron beams. This is a very thin piece of metal (or a gri…

> This is a very thin piece of metal (or a grid of thin wires in certain cases) that is easily magnetized.

Worse, a strong magnet (especially a modern rare-earth magnet) can bend the shadow mask, causing color distortion which can't be corrected by degaussing.

Re: Did I destroy my friend's TV with a magnet? (2022)

#17

Post by hammyhavoc »

ksaj wrote: post #12
kamilner wrote: post #2

There's a throwaway comment in here about the earth's magnetic field affecting CRTs and turning the TV upside down, is that actually true? I would have thought the earth's magnetic field would be incredibly weak in comparison to the deflecting coils.

I just sent an email to my old high school buddy. I'm sure this is incorrect, and I've asked him for his remembrance of something we did on a lark. One night David Letterman did an episode where throughout the show, the camera(s) did a full 360 degree revolution. When the show was half-way through, it was of course, upside down. So we turned the television upside down. I personally don't remember anything unusual abo…

People frequently rotate CRTs for arcade games. They're fine.

Re: Did I destroy my friend's TV with a magnet? (2022)

#18

Post by ksaj »

hammyhavoc wrote: post #17
ksaj wrote: post #12

Earlier quoted context omitted.

I just sent an email to my old high school buddy. I'm sure this is incorrect, and I've asked him for his remembrance of something we did on a lark. One night David Letterman did an episode where throughout the show, the camera(s) did a full 360 degree revolution. When the show was half-way through, it was of course, upside down. So we turned the television upside down. I personally don't remember anything unusual abo…

People frequently rotate CRTs for arcade games. They're fine.

Actually, this is a perfectly good point - arcade games had their CRTs on a 45 degree angle, some on portrait and some on landscape direction, and they showed no "intermediate" effects that you'd expect if this gravity claim was true. There were even "table" video games where the CRT was 90 degrees upward, which should have really messed things up if this gravitational effect was at all true.

Likewise, remember the green swooping radar of days gone by? In wartime, those regularly got a wild ride through gravity, and yet you never hear of them having a problem with it.

I'm really thinking this article's "throw-away" comment is really worth throwing away.

Re: Did I destroy my friend's TV with a magnet? (2022)

#19

Post by simonblack »

All quality CRT TVs are automatically de-gaussed on switch-on. That's the 'toooong' you hear when they turn on.

A magnet might temporarily mess up the magnetic convergence with magnetised spot areas, but that should be fixed on next switch-on.

The Earth’s magnetic field can also affect the picture

That's because when the convergence controls are set correctly, they also take care of the magnetic field of the earth too at the same time. If you turn the TV upside down, you would also have to reset the convergence controls. No biggie, but it is something that needs doing.

Re: Did I destroy my friend's TV with a magnet? (2022)

#20

Post by NoZebra120vClip »

One time when I was very young, I was already such a tech-nerd that I chose to attack my father with a magnet, intended to damage his wristwatch.

I was calmly informed that he'd already selected a watch that was immune to magnetic fields. But of course that was a real danger to old-fashioned movements which had many ferrous parts that relied on not sticking together.

I never lived it down. Some of our childish rebellions are ridiculous in retrospect!

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