georgeh@cognos.UUCP (George Hagilaris) (11/29/89)
Hi. A friend of mine is having a strange problem with his monitor and I was
wondering if someone on the net may have an idea of what is causing it.
The monitor is a monochrome graphic display Packard Bell monitor. The model
number is PB 1272A. He has it hooked up to an XT clone (IBC) with a Hercules
card.
The problem is that a faint amber glow (it's an amber monitor) is forming on
the upper right side of the screen. The glow sometimes gets brighter and then
fades away again. Sometimes the glow will flicker a bit. The monitor is still
useable since the text is still brighter than the glow is, but the problem
is starting to get worse. When it's at its brightest, the glow will cover
almost half the screen, but that doesn't last very long (and the text is still
brighter). Does anyone have any idea what the cause might be? Someone
mentioned to my friend that some kind of magnetic field may have formed and
that the monitor needs to be de-Gaussed (sp?). If this is true, how do you go
about de-gaussing a monitor? Is it possible that it could be a problem with
the graphics card (doesn't seem like it)?
The monitor is just over a year old and the problem has never occurred before.
The problem _just_ started about an hour ago, so it could get a lot worse very
soon. If anyone has any ideas, please help. Thanks.
George
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_ _ _ _ _
George Hagilaris / / \ / _ |\ | / \ |_
UUCP: uunet!mitel!sce!cognos!georgeh \_ \_/ \_| | \| \_/ _| INC.lpb@cbnewsi.ATT.COM (louis.p.barbuscio) (12/01/89)
It does sound like degausing would help. Basically Cathode Ray Tubes
consist of an electron beam aimed at a phosphor screen and focused and
deflected by electro magnetic coils wrapped around the neck of the
tube. All these magnetic fields sometimes have the effect of magnetizing
things in the vicinity of the screen which results in the kind of haloing
or shadowing you are experiencing. The way to get rid of this is simnply
to take a large coil of wire and connect some AC power to it and move it
around the screen like a divining rod (The coil is referred to as a degausing
coil and you can probably get a commercially made one from Radio Shack).
You might get the same affect by taking one of those plug/transformer
power adapters, like the ones used for battery adapters, plug it into
an extension cord and wave it around the screen. The trick is to slowly
increase the distance between the screen and the coil. Sudden movements
have the effect of leaving the spot magnetized.
Finally, it should be noted that most (if not all) modern Color TV's
and I suspect PC monitors have built in degausing coils that operate
every time the monitor is powered up. It's a cheap circuit (2 turns
of wire around the face of the tube and a timed pulse of AC while the
power supply is getting up to speed. Of course if you never turn the
monitor off it never operates. Or it may be inoperative in your monitor.
You can check for the presence of a working built in degausing coil by
doing the following:
1: Take a small permanent magnet (the kind you use to stick things
on your refigerator) put it against a spot near the edge of your
PC screen. You will notice that when you take it away a spot
remains on the screen.
2: Power down the monitor and turn it on again, if the monitor has
its own degausing coil the spot will be gone. If not, well it's
time to find the AC adapter for your kids SONY Walkmen and start
doing the degausing boogie.
_____________________________________________________________________________
Lou Barbuscio, AT&T Bell Labs, Holmdel NJ, lpb@cbnewsi 201-949-7687
Disclaimer: | "Happy the man whose mouth (or
After 34 years I'm not sure if I speak| keyboard) brings him no grief "
for the company or it speaks for me. | Sirach 14:1poffen@molehill (Russ Poffenberger) (12/05/89)
In article <1337@cbnewsi.ATT.COM> lpb@cbnewsi.ATT.COM (louis.p.barbuscio,ho,) writes: >It does sound like degausing would help. Basically Cathode Ray Tubes >consist of an electron beam aimed at a phosphor screen and focused and >deflected by electro magnetic coils wrapped around the neck of the >tube. All these magnetic fields sometimes have the effect of magnetizing >things in the vicinity of the screen which results in the kind of haloing >or shadowing you are experiencing. The way to get rid of this is simnply >to take a large coil of wire and connect some AC power to it and move it >around the screen like a divining rod (The coil is referred to as a degausing >coil and you can probably get a commercially made one from Radio Shack). >You might get the same affect by taking one of those plug/transformer >power adapters, like the ones used for battery adapters, plug it into >an extension cord and wave it around the screen. The trick is to slowly >increase the distance between the screen and the coil. Sudden movements >have the effect of leaving the spot magnetized. > Keep in mind the original posting. He stated quite clearly that the monitor was an amber monitor. This obviously implies monochrome. Monochrome monitors don't have degaussing circuits, nor have I ever known one to need it. Certainly no harm should come to the monitor if done correctly, but I doubt seriously that it will help. There is probably something wrong with it. Either that or maybe he has something in close proximity to the monitor that generates a magnetic field. Russ Poffenberger DOMAIN: poffen@sj.ate.slb.com Schlumberger Technologies UUCP: {uunet,decwrl,amdahl}!sjsca4!poffen 1601 Technology Drive CIS: 72401,276 San Jose, Ca. 95110 (408)437-5254
pipkins@qmsseq.imagen.com (Jeff Pipkins) (12/05/89)
I've heard that you can just run a decent magnet over the surface of the monitor to fix the burned-in image problem. I don't know whether it is true, I've never tried it. I've heard similar rumors about those bulk cassette tape erasers based on electromagnets. Try it only at your own risk. Apply standard disclaimers here.
kurtk@tekcae.tek.com (Kurt Krueger) (12/06/89)
All sorts of stuff can cause a glow on a TV type tube. Try checking for the
following:
1. Overscan. The beam is striking the sides of the tube. Adjust if possible.
2. Gas. Turn the whole screen on. If it is serious enough you will see a cross
pattern. Otherwise, if you can see the neck of the tube, check the "getter"
material (the blackish, silverish spot). If it has white fringes, you have
gas. Time for a new tube.
3. Junk/crud. Some small piece of metal, glass, or phosphor has gotten near the
the high voltage end of the tube. Not much you can do. You might be able
to dislodge it by shaking the monitor but if there is loose junk inside you
may make matters worse. Don't get rough with the tube, they do break and
are potential bombs.
4. Maybe all the smoke leaked out :-) .
________________________________________________________________________________
|
kurtk@tekcae.CAX.TEK.COM (Kurt Krueger) | Everything runs on smoke. When the
Electrical Simulation Group (ECAX) | smoke leaks out, it stops working.
Ex CRT designer |
D.S. 59-432 (503) 627-4363 |
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