Inductor with a Magnet

[Graham W]

"Watson A.Name "Watt Sun - the Dark Remover"" <NOSPAM@dslextreme.com>
wrote in message news:bor1aa$4qg7b$1@hades.csu.net...

Graham W wrote:

Watson A.Name - Watt Sun, Dark Remover wrote:

I pulled some ferrite core chokes out of a Compaq monitor and one had
a magnet on the top, held on by heat shrink tubing. I measured the
inductance with the magnet on, and it measured 8.2 uH. I cut off the
HST and removed the magnet, and the inductance shot up to 35 uH. I
think this has something to do with varying the permeability.

I don't remember seeing anything about this kind of choke in any
electronics manuals, so I thought I'd do a web search but I came up
with nothing. I tried magnetically polarized inductor and magnetic
core inductor, but neither gave any info that I could find. Do you
know what they call these devices? Thank you.


It is a horizontal linearity control.

But it doesn't have any adjustment.

The core in the coil may screw up and down OR the magnet may in a
rotatable clip (unlikely in your item) OR there may be another coil in
series with this one. Review the horizontal deflection circuits of as
many TVs and monitors as you can find and you will see it is a very
common component.


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[Mark Jones]

In news:6wasb.7090$lm1.49559@wards.force9.net (Graham W):

"Watson A.Name "Watt Sun - the Dark Remover"" <NOSPAM@dslextreme.com
wrote in message news:bor1aa$4qg7b$1@hades.csu.net...
Graham W wrote:

Watson A.Name - Watt Sun, Dark Remover wrote:

I pulled some ferrite core chokes out of a Compaq monitor and one had
a magnet on the top, held on by heat shrink tubing. I measured the
inductance with the magnet on, and it measured 8.2 uH. I cut off the
HST and removed the magnet, and the inductance shot up to 35 uH. I
think this has something to do with varying the permeability.

I don't remember seeing anything about this kind of choke in any
electronics manuals, so I thought I'd do a web search but I came up
with nothing. I tried magnetically polarized inductor and magnetic
core inductor, but neither gave any info that I could find. Do you
know what they call these devices? Thank you.


It is a horizontal linearity control.

But it doesn't have any adjustment.

The core in the coil may screw up and down OR the magnet may in a
rotatable clip (unlikely in your item) OR there may be another coil in
series with this one. Review the horizontal deflection circuits of as
many TVs and monitors as you can find and you will see it is a very
common component.

A customer called in today, storms went through her area and both her TV
and monitor are hosed. The TV's image is "pinched," and the monitor's image
is "skewed" and "all color-banded like the old TV's were."

What do you think... electrical damage, or EMI magnetization?

 

[Watson A.Name - "Watt Sun]

In article <Ws6dnaISOOdSMCyi4p2dnA@buckeye-express.com>, "Mark Jones"
<127.0.0.1> mentioned...

In news:6wasb.7090$lm1.49559@wards.force9.net (Graham W):
"Watson A.Name "Watt Sun - the Dark Remover"" <NOSPAM@dslextreme.com
wrote in message news:bor1aa$4qg7b$1@hades.csu.net...
Graham W wrote:

Watson A.Name - Watt Sun, Dark Remover wrote:

I pulled some ferrite core chokes out of a Compaq monitor and one had
a magnet on the top, held on by heat shrink tubing. I measured the
inductance with the magnet on, and it measured 8.2 uH. I cut off the
HST and removed the magnet, and the inductance shot up to 35 uH. I
think this has something to do with varying the permeability.

I don't remember seeing anything about this kind of choke in any
electronics manuals, so I thought I'd do a web search but I came up
with nothing. I tried magnetically polarized inductor and magnetic
core inductor, but neither gave any info that I could find. Do you
know what they call these devices? Thank you.


It is a horizontal linearity control.

But it doesn't have any adjustment.

The core in the coil may screw up and down OR the magnet may in a
rotatable clip (unlikely in your item) OR there may be another coil in
series with this one. Review the horizontal deflection circuits of as
many TVs and monitors as you can find and you will see it is a very
common component.


A customer called in today, storms went through her area and both her TV
and monitor are hosed. The TV's image is "pinched," and the monitor's image
is "skewed" and "all color-banded like the old TV's were."

What do you think... electrical damage, or EMI magnetization?

I think she'd be better off with a flat panel display. :-O

Try the degaussing coil and if that doesn't fix it, then it seems to
be something more serious.

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