Questions on convergence...

Barry Watzman Watzman at
Sun Aug 13 10:30:54 CDT 2006

Convergence is the adjustment by which a monitor or TV properly overlaps the
3 separate red, blue and green images to produce a proper color image.  It
applies to all CRT based TV sets and monitors except those using a single
image forming module for all 3 colors (e.g. DLP and most (but not all) LCD
projectors, and LCD and plasma screens).

Normally there are two steps, the first is "static convergence" in which the
3 images (red, blue and green) are adjusted to overlap at the exact center
of the screen.  The second is dynamic convergence in which the rest of the
screen is "converged".  Note that "perfect" convergence is generally not
possible, but modern devices get very close.  Also note that on some newer
CRTs, some or all of the convergence adjustments are fixed at the factory
and cannot be adjusted.

Static convergence is usually adjusted using magnets on the CRT neck (again,
common practice today is that these are set at the factory and then epoxy
glued).  Dynamic convergence is complex, if it's adjustable at all there can
be as many as 30-40 controls effecting different colors in different parts
of the screen.  You also need a test pattern generator to make this
adjustment (although on a computer (vs. a TV), you might be able to do it
with a black screen and the letter "H" in various places).

I can't give you any help for your specific device, you need to locate a
service manual or you probably won't be able to do much with it.

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