Did I destroy my friend's TV with a magnet? (2022)
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Re: Did I destroy my friend's TV with a magnet? (2022)
#2There'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.
Re: Did I destroy my friend's TV with a magnet? (2022)
#3Is 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?
Re: Did I destroy my friend's TV with a magnet? (2022)
#4Is 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 grid of thin wires in certain cases) that is easily magnetized.
Re: Did I destroy my friend's TV with a magnet? (2022)
#5There'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.
Correct, the field of the Earth is weak and won’t mess up the image on the TV.
Re: Did I destroy my friend's TV with a magnet? (2022)
#6Is 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…
And can be repaired, most of the time, with a degaussing coil.
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.
Re: Did I destroy my friend's TV with a magnet? (2022)
#7There'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.
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 90's. the reversal in the Earth's magnetic field between the northern and southern hemisphere's meant I could never completely get the RGB guns to line up correctly.
Re: Did I destroy my friend's TV with a magnet? (2022)
#8There'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've had TVs move room to room and face a different direction and need to be fixed with a degaussing coil. I'm told it's from the Earth's magnetic field. Could also be that they were next to other TVs (arcade machines in this case).
Re: Did I destroy my friend's TV with a magnet? (2022)
#9Earlier quoted context omitted.
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…
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.
Re: Did I destroy my friend's TV with a magnet? (2022)
#10Is 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…
I can't believe the author skipped this part. I felt terrible unsatisfied with the article. Thank you!