Originally from : "Budi Lewiyanto" <[EMAIL PROTECTED]>
Originally dated: Thu, 30 Dec 1999 11:32:09 +0700
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<e-Software>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~Forum Diskusi Software dan Internet untuk Kristen-Katholik~~~~~~~
Dear Pak Ronny,
Memang pakai logam tapi logam yang ber aliran Magnet yang kuat.
dibawah ini saya copykan informasinya :-)
Question :
My four-year-old son was fooling around with a magnet, and when I was turned
away, put it right on our TV screen. I then saw him doing this, and before I
could bring myself to think consequences, we were both mollified by the
amazing and colorful patterns it created on the screen. He sort of moved it
around the screen, like you would an eraser on a black board. Well, when he
removed the magnet, the screen had been drained of its normally saturated
colors, and what we now have left is a color TV with only three colors,
basically green, blue, and red. And they are not solid and deep like they
were before. They are rather faded, and arranged in three distinct blotches,
if you will. Are we stuck with this situation forever, or will this
aberration fade with time, back to normal? And, why did this happen? --
E-S.B.
Answer :
Your son has magnetized the shadow mask that's located just inside the
screen of your color television. It's a common problem and one that can
easily be fixed by "degaussing" the mask (It'll take years or longer to fade
on its own, so you're going to have to actively demagnetize the mask). You
can have it done professionally or you can buy a degaussing coil yourself
and give it a try (Try a local electronics store or contact MCM Electronics,
(800) 543-4330, 6" coil is item #72-785 for $19.95 and 12" coil is item
#72-790 for $32.95).
Color sets create the impression of full color by mixing the three primary
colors of light--blue, green, and red--right there on the inside surface of
the picture tube. A set does the mixing by turning on and off three separate
electron beams to control the relative brightnesses of the three primary
colors at each location on the screen. The shadow mask is a metal grillwork
that allows the three electrons beams to hit only specific phosphor dots on
the inside of the tube's front surface. That way, electrons in the "blue"
electron beam can only hit blue-glowing phosphors, while those in the
"green" beam hit green-glowing phosphors and those in the "red" beam hit
red-glowing phosphors. The three beams originate at slightly different
locations in the back of the picture tube and reach the screen at slightly
different angles. After passing through the holes in the shadow mask, these
three beams can only hit the phosphors of their color.
Since the shadow mask's grillwork and the phosphor dots must stay perfectly
aligned relative to one another, the shadow mask must be made of a metal
that has the same thermal expansion characteristics as glass. The only
reasonable choice for the shadow mask is Invar metal, an alloy that
unfortunately is easily magnetized. Your son has magnetized the mask inside
your set and because moving charged particles are deflected by magnetic
fields, the electron beams in your television are being steered by the
magnetized shadow mask so that they hit the wrong phosphors. That's why the
colors are all washed out and rearranged.
To demagnetize the shadow mask, you should exposed it to a rapidly
fluctuating magnetic field that gradually decreases in strength until it
vanishes altogether. The degaussing coils I mentioned above plug directly
into the AC power line and act as large, alternating-field electromagnets.
As you wave one of these coils around in front of the screen, you flip the
magnetization of the Invar shadow mask back and forth rapidly. By slowly
moving this coil farther and farther away from the screen, you gradually
scramble the magnetizations of the mask's microscopic magnetic domains. The
mask still has magnetic structures at the microscopic level (this is
unavoidable and a basic characteristic of all ferromagnetic metals such as
steel and Invar). But those domains will all point randomly and ultimately
cancel each other out once you have demagnetized the mask. By the time you
have the coil a couple of feet away from the television, the mask will have
no significant magnetization left at the macroscopic scale and the colors of
the set will be back to normal.
Incidentally, I did exactly this trick to my family's brand new color
television set in 1965. I had enjoyed watching baseball games and deflecting
the pitches wildly on our old black-and-white set. With only one electron
beam, a black-and-white set needs no shadow mask and has nothing inside the
screen to magnetize. My giant super alnico magnet left had no linger effect
on it. But when the new set arrived, I promptly magnetized its shadow mask
and when my parent watched the "African Queen" that night, the colors were
not what you'd call "natural." The service person came out to degauss the
picture tube the next day and I remember denying any knowledge of what might
have caused such an intense magnetization. He and I agreed that someone must
have started a vacuum cleaner very close to the set and thus magnetized its
surface. I was only 8, so what did I know anyway.
Finally, as many readers have pointed out, many modern televisions and
computer monitors have built-in degaussing coils. Each time you turn on one
of these units, the degaussing circuitry exposes the shadow mask to a
fluctuating magnetic field in order to demagnetize it. If your television
set or monitor has such a system, then turning it on and off a couple of
times should clear up most or all of the magnetization problems. However,
you may have to wait about 15 minutes between power on/off cycles because
the built-in degaussing units have thermal protection that makes sure they
cool down properly between uses.
-----Original Message-----
From: Ronny Purwadi <[EMAIL PROTECTED]>
To: e-Software <[EMAIL PROTECTED]>
Date: Thursday, December 30, 1999 10:21 AM
Subject: [i-kan-software] Re: Speaker ?
Originally from : Ronny Purwadi <[EMAIL PROTECTED]>
Originally dated: Thu, 30 Dec 1999 10:14:38 +0700
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<e-Software>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~Forum Diskusi Software dan Internet untuk Kristen-Katholik~~~~~~~
Kalau magnetic field, apa mungkin bisa dihalangin pake logam ??
rp-
Budi Lewiyanto wrote:
I-KAN %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% e-Software
Permulaan hikmat adalah takut akan TUHAN! Mazmur 111:10a / Amsal 9:10a
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