[time-nuts] [OT] degaussing

Max Robinson max at maxsmusicplace.com
Sat Apr 17 22:09:00 EDT 2010

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.


Max.  K 4 O D S.

Email: max at maxsmusicplace.com

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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 
>> :)
>>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 
>>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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