One of the great things about flat-panel displays is that they don't need
purity or convergence adjustments. I'd like to tell you about two purity
problems I've had with my own equipment (hmmm...) and get your views on the
second.

Case 1: When I purchased a Toshiba CZ-3299K IDTV, the set arrived with a
severe impurity splotch at the lower-right corner. This appeared to have
been caused by a shock to the shadow mask during shipping. I put up with it,
until I moved to a condo in 1998. Lo and behold, the splotch vanished! The
"shaking about" during the move must have de-warped the shadow mask, or
perhaps knocked it back into place.

Case 2: About five years ago, someone in this group had a question about
removing impurities. In my desire to demonstrate that there was no degree of
magnetization that could not be removed, * I held a bulk-tape eraser
designed for metal-particle tape near the lower-right of my 400-series Sony
WEGA IDTV, and shut it off. Naturally, the aperture grille was badly
magnetized. Much to my dismay, I could not completely remove the impurity!

It persisted, in varying degrees, until yesterday. I had the Magnolia guys
move the set into the bedroom -- and it was gone! (I should note that the
set now sits at 90 degrees with respect to its initial position. But it's
unlikely that the original impurity had anything to do with the Earth's
field. There was no impurity before I'd "zapped" the set.)

Thoughts, anyone?

* This is at least theoretically true, as there is a limit to how much any
magnetic substance can be magnetized, and it cannot be greater than the
magnetizing force. (I think.) (Please note that I'm talking about magnets,
not solenoids.)

On Mar 22, 7:15*am, "William Sommerwerck"
wrote:
One of the great things about flat-panel displays is that they
don't need
purity or convergence adjustments. I'd like to tell you about two
purity
problems I've had with my own equipment (hmmm...) and get your
views on the
second.

Case 1: When I purchased a Toshiba CZ-3299K IDTV, the set arrived
with a
severe impurity splotch at the lower-right corner. This appeared to
have
been caused by a shock to the shadow mask during shipping. I put up
with it,
until I moved to a condo in 1998. Lo and behold, the splotch
vanished! The
"shaking about" during the move must have de-warped the shadow
mask, or
perhaps knocked it back into place.

Case 2: About five years ago, someone in this group had a question
about
removing impurities. In my desire to demonstrate that there was no
degree of
magnetization that could not be removed, * I held a bulk-tape
eraser
designed for metal-particle tape near the lower-right of my 400-
series Sony
WEGA IDTV, and shut it off. Naturally, the aperture grille was
badly
magnetized. Much to my dismay, I could not completely remove the
impurity!

It persisted, in varying degrees, until yesterday. I had the
Magnolia guys
move the set into the bedroom -- and it was gone! (I should note
that the
set now sits at 90 degrees with respect to its initial position.
But it's
unlikely that the original impurity had anything to do with the
Earth's
field. There was no impurity before I'd "zapped" the set.)

Thoughts, anyone?

* This is at least theoretically true, as there is a limit to how
much any
magnetic substance can be magnetized, and it cannot be greater than
the
magnetizing force. (I think.) (Please note that I'm talking about
magnets,
not solenoids.)

I don't know about the Toshiba but on Sony I had a broadcast BVM-1910
that got the aperture grille wires criss-crossed from a hand held
degaussing coil. On a tour at the San Diego Sony plant in '86 I saw a
guy whose job it was to hit each new CRT (hanging conveyor) in the
face with a rubber mallet. 3 or 4 smacks later, the monitor was fine
again. Sometime percussive maintenance works.

G²

...I had a broadcast BVM-1910 that got the aperture grille wires
criss-crossed from a hand-held degaussing coil. On a tour at the
San Diego Sony plant in '86 I saw a guy whose job it was to hit
each new CRT (hanging conveyor) in the face with a rubber mallet.
3 or 4 smacks later, the monitor was fine again. Sometime percussive
maintenance works.

The thought of "whacking" the faceplate never crossed my mind. The small
vibrations of moving the set and laying it down on another stand must have
been enough to "detangle" the wires.