[HN Gopher] Did I destroy my friend's TV with a magnet? (2022)
___________________________________________________________________
Did I destroy my friend's TV with a magnet? (2022)
Author : reqo
Score : 6 points
Date : 2024-01-03 19:00 UTC (4 hours ago)
(HTM) web link (www.fleet.org.au)
(TXT) w3m dump (www.fleet.org.au)
| kamilner wrote:
| 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.
| db48x wrote:
| Correct, the field of the Earth is weak and won't mess up the
| image on the TV.
| degauss wrote:
| 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.
|
| https://www.webopedia.com/insights/monitorhemispheres/
| cardiffspaceman wrote:
| 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.
| TheBigSalad wrote:
| 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).
| lukev wrote:
| 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?
| db48x wrote:
| 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.
| joezydeco wrote:
| 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.
| lukev wrote:
| 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.
| lopis wrote:
| I can't believe the author skipped this part. I felt terrible
| unsatisfied with the article. Thank you!
___________________________________________________________________
(page generated 2024-01-03 23:02 UTC)