[time-nuts] [OT] degaussing

Mon Apr 26 04:34:35 UTC 2010

When I moved from England to New Zealand I brought my Sony Trinatron
TV with me and had the tuner replaced so it would work over here (we
still have VHF TV and a different sound sub-carrier). The set worked
fine after the conversion and I noticed no problems at all with the
picture but that's not to say that the REALLY good TV guy had not
sorted things out.

Steve

On 26 April 2010 03:51, Henk <henk at deriesp.demon.nl> wrote:
> Hi,
>
> 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.
>
> Henk
>
>
> 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
>> Vacuum tube site: http://www.funwithtubes.net
>> Music site: http://www.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
>>>> 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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>>
>>
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-- 
Steve Rooke - ZL3TUV & G8KVD
A man with one clock knows what time it is;
A man with two clocks is never quite sure.