[time-nuts] [OT] degaussing
Arnold.Tibus at gmx.de
Sat Apr 17 12:04:41 UTC 2010
The dotpitch of Trinitron and Diamondtron tubes (Mitsubishi)
is at 1/100 inch (0.24 mm to 0.27 mm), which defines the distance
of these shadow wires. What tube width do you have? ;-)
The wires are very sensitive to vibrations which makes the horizontal
stabilizing wires necessary (in most cases 2, max. 3). These are visible
with a bright and uniform picture.
All such tubes are equipped with a degaussing system
(electromagnetic coil in a black hose) which are normally activated
always when switching the monitor/ TV on. There is normally no
forther degaussing needed.
One can apply stronger magnetic fields from the front side by using
cannibalized coils in parallel with an adequate 50/ 60 Hz system
stepping the field continuously down. Attention, strong dc H- fields
may result in sticking some wires together, which may be very
difficult to get it corrected!
The small magnets on the back of the tube are necessary to
linearize the dynamic field of the deflecting coil and to compensate
other small steady magnetic distortions around the tube.
There are some more magnets on the neck of the tube for
convergence and beam forming.
A long and distracting work to to when you had to replace the tube
or coils and then to adjust for white and clean colors and sharp
Older systems needed an earth field compensation in situ.
(Don't try it when you are not experienced with it, you will turn crazy -
and the professional serviceman later will as well!)
On Fri, 16 Apr 2010 21:05:31 EDT, SAIDJACK at aol.com wrote:
>point of trivia:
>can you count how many vertical wires are strung across a Trinitron
>monitors' shadow mask??
>I used to work at Sony for a long time, we had a TV assembly line next door
>If you can see the vertical wires, you still have very good eyesight...
>In a message dated 4/16/2010 04:55:35 Pacific Daylight Time,
>cfharris at erols.com writes:
>Are they really? For some reason, every Trinitron I have ever seen
>has clusters of little stick on magnets placed here and there on the
>back of the glass envelope.
>The trinitron has a shadowmask. It is a grill of highly tensioned wires
>that are positioned just behind the screen. The original trinitron tube
>was a little 5 inch diagonal CRT. It had to be small because the wires
>tended to vibrate if the set was bumped, and that made for some very odd
>displays. The later larger tubes had horizontal titanium wires welded to
>the backs of the shadow mask wires every 5 or 10 inches, to prevent the
>psychedelic color fest that happened when the CRT got bumped.
>The trinitron has three very carefully aligned cathodes in the gun. They
>are positioned side-by-side, creating the slight different projection
>angles necessary to cause the long vertical slots formed by the shadow mask
>to eclipse the appropriate color bands on the screen.
>I'm not sure what you are describing; it sure sounds cool; but it isn't
>Can you find some references? I'd like to read up on it.
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