Michael Shell wrote in
news:20100228004851.0c71229b@bashir:

On Sat, 27 Feb 2010 20:25:26 -0800
David Nebenzahl wrote:

Well, I tried cleaning the dust out of my Dell-branded Trinitron tube.
In so doing I seem to have knocked the convergence out of whack, even
though I was really careful vacuuming around the CRT.

There's an on-screen convergence control, but even with it cranked all
the way over (to 100/100 for the horizontal control, 76 for the
vertical), there are still highly visible "ghosts" on screen.


Try demagnetizing it first, especially if your monitor has a built-in
degaussing button. The next step is to degauss with an external
demagnitizer. There are TV degaussing coils for this (check Ebay), but
you might be able to make do with something like a bulk tape eraser
if you already have one.

Color convergence problems will show up as red, blue or green outlines
and/or duplicate images - like when the colors don't align on newspaper
comic sections. If the ghosts you see are not in different colors,
then it is not a convergence problem. The focus control is often very
easy to unintentionally turn although a misadjusted focus control
generally causes blurriness rather than ghosts.


Cheers,

Mike Shell




first,there's a difference between "convergence" and "purity".

when setting up a CRT,you first adjust purity,by displaying a red screen
and adjusting yoke magnets for even color and no green or blue areas.
But before that,you degauss with an EXTERNAL coil,as the internal coils are
not powerful enough.

Convergence is adjusted by displaying a crosshatch or dot grid and
adjusting the appropriate controls to merge the R-G-B lines or dots to make
white lines or dots.
On some sets,you may also have to use adhesive magnet strips to achieve
decent convergence in the corners.I used to do this at Tektronix on their
650 and 670 series monitors.

--
Jim Yanik
jyanik
at
localnet
dot com