[time-nuts] [OT] degaussing

Henk henk at deriesp.demon.nl
Sun Apr 25 11:51:21 EDT 2010


Up to the Philips 20AX tubes they used adjustable multipole units  
around the neck of the tube. These multipoles can be readjusted if  
needed. From the 30AX design on, the used multipoles that were  
internal, thus inside the neck. The required correction was measured  
during manufacture and the internal multipole magnetized.  Turning the  
tube upside down will help down under if the tube was manufactured in  
the northern hemisphere. Then tune the deflection yoke back or swap  
line and frame connections.


Op 18 apr 2010, om 04:09 heeft Max Robinson het volgende geschreven:

> I haven't been following this thread but here are my comments based  
> on the attached messages.  You may have difficulty finding a service  
> technician who knows how to adjust purity and convergence on a CRT.   
> In about 1975 they started coming from the factory with deflection  
> yokes installed and all purity and convergence adjusted.
> Regards.
> Max.  K 4 O D S.
> Email: max at maxsmusicplace.com
> Transistor site http://www.funwithtransistors.net
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> ----- Original Message ----- From: "Arnold Tibus"  
> <Arnold.Tibus at gmx.de>
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com 
> >
> Sent: Saturday, April 17, 2010 7:04 AM
> Subject: Re: [time-nuts] [OT] degaussing
>> 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
>> picture...%-))
>> 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!)
>> greetings,
>> Arnold
>> 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...
>>> bye,
>>> Said
>>> 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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