[time-nuts] [OT] degaussing

Arnold Tibus Arnold.Tibus at gmx.de
Sat Apr 17 08:04:41 EDT 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
>a trinitron.

>Can you find some references?  I'd  like to read up on it.

>-Chuck  Harris

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