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  1. #1

    Default northern hemisphere picture tubes & todays tip.

    From another posting there is;

    > Billy's tip: If you brought your screen in from overseas, it may be a Northern Hemisphere model and could need several degausses to get right, if it comes right at all. If in doubt, turn it upside down and degauss. If it looks ok upside down, that's the answer. Either take up Yoga or buy a new screen. This effect gets worse the further south you travel. I kid you not, would Billy lie?

    I would like to say that I have converted many UK TV to NZ sound and never noticed a problem with color purity,

    The only problem I get is were NZ TV parts suppliers supply sound take off components BUT no sound traps to stop sound interference on the picture, yet in Australia these components are available, it makes it look like NZ TV service people don't understand their TV theory.


    Sorry about the weeds growing,

    Also if you decide to clean your CRT screen, never spray your screen with cleaning liquid either for your monitor or the TV, as the cleaning liquid drips and-or runs down into the electronic user controls and other components and corrodes them, requiring earlier service.

  2. #2

    Default Re: northern hemisphere picture tubes & todays tip.

    Isn't the degaussing in relation to the magnetic pull that evolves from the earth. in the northern hemisphere, it is pulling in the opposite direction.

  3. #3
    Terry Porritt

    Default Re: northern hemisphere picture tubes & todays tip.

    Perhaps TVs are not so critical. I understand there was a batch of Compaq 14" vga northern hemisphere monitors brought in about 1990, I only saw 2nd hand ones but all these lacked convergence, quite badly.
    Its more than just degaussing, its the little magnetic correction bits that are stuck on to compensate that are different.
    As well as the G-M angle, the Dip angle is also quite different here as can be noticed if you try to use your NZ compass in the northern hemisphere.

  4. #4
    Billy T

    Default Re: northern hemisphere picture tubes & todays tip.

    Hi E.ric

    Picture tubes are not only made for northern and southern hemispheres, some time back I recall seeing some optimised for extreme northern or southern latitudes.

    I too have converted many UK sets to NZ standards and you are right, most can be set up for good purity but it gets harder and harder to get it right the further south you go. Also, centering of the picture is more difficult the further south you go. To simulate this, set up a test pattern on your tv or monitor and turn it upside down. You will find that the pix has moved sideways. Years ago in the days of B&W tv there was a very early console set made by PYE that could be serviced through the bottom of the chassis if you stood it on its head. That was quicker than removing the chassis completely. If you centered the pix while upside down it would be incorrect when you stood it up again.

    A little more recently (but still ancient history) CEI's TVC2 chassis lacked vertical and horizontal centering controls. To centre the pix vertically you had to add a 330 ohm bleeder across the vertical scan coil coupling cap, and out of tolerance horizontal needed a small horizontal shift circuit added. The latter was more often required in the South Island because of the additional shift caused by the lower latitude. We put it down to CEI buying the wrong CRTs. We installed one upside down once to prove the point and the pix was perfectly centred Of course the quick answer was to increase the width but in the days of all morning test patterns (remember test patterns?) customers often complained that the picture was not in the centre of the screen.

    Now that CRTs have (semi) fixed convergence and purity adjustments one that is a little out of tolerance might show purity errors that cannot be corrected by degaussing alone.

    I stand to be corrected of course, but I am unaware of any technological advance that can compensate for the different geomagnetic field characteristics between hemispheres.


    Billy 8-{)

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