NotTaR of Television Sets : B/W TV size, position, and geometry adju..  
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B/W TV size, position, and geometry adjustments

These tend to be a lot simpler and less critical than for color monitors or TV sets.

On a B/W TV you will probably see some of the following adjustments:

  1. Position - a pair of rings with tabs on the neck of the CRT. There may be electronic position adjustements as well though this is not that common on small TVs.

  2. Width and height (possibly linearity as well) controls. There may be some interaction between size and linearity - a crosshatch test pattern is best for this. Vertical adjustments are almost always pots while horizontal (if they exist) may be pots and/or coils. Size will normally be set for 5-10% overscan to account for line voltage fluctuations and component drift. Confirm aspect ratio with test pattern which includes square boxes.

  3. Geometry - some little magnets either on swivels around the yoke or glued to the CRT. If these shifted, the the edges may have gotten messed up - wiggles, dips, concave or convex shapes. There may be a doxen or more each mostly affecting a region around the edge of the raster. However, they will not be totally independent.

Check at extremes of brightness/contrast as there may be some slight changes in size and position due to imperfect HV regulation.

There may be others as well but without a service manual, there is no way of knowing for sure. Sams' often has folders for B/W TVs.

Just mark everything carefully before changing - then you will be able to get back where you started.

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