REIDMP@MAINE.BITNET (Reid M. Pinchback) (03/29/91)
I've just started using a PC clone of TeX (emTeX). I noticed that the
vertical-to-horizontal screen proportions are close to the horizontal-
to-vertical proportions of an 8.5x11 sheet of paper. By rotating the
page image 90 degrees and setting the monitor on its side, you get a
good full-screen view of what the page will look like.
But... (there always seems to be a but, somewhere)
When I set the VGA monitor on its side, there is a strange distortion of
colour. It is the 800x600 resolution VGA monitor that comes with the
AT&T 6386 WGS (a 386 clone). The card is AT&T's VDC 600. Most of this
AT&T PC stuff is manufactured by Olivetti.
Questions:
1. What causes the colour distortion?
2. Is there a way to fix it?
3. Is it harmful to the monitor to use it on its side?
Thanx in advance
Reidiisakkil@vipunen.hut.fi (Mika R Iisakkila) (03/30/91)
REIDMP@MAINE.BITNET (Reid M. Pinchback) writes: > When I set the VGA monitor on its side, there is a strange distortion of > colour. > 1. What causes the colour distortion? It's the magnetic field of the Earth. The VGA pixels are so close to each other, that this weak magnetic field is enough to make electron beams to land on wrong pixels (=phosphor dots of wrong colour). The monitor contains numerous magnets, which are adjusted to compensate for the magnetic field. The calibration has of course been made to work in the normal position of the monitor. Actually, if you took your monitor to somewhere on the southern hemiglobe (sp?), say Australia, the colours would be distorted while the monitor is standing normally on the table! > 2. Is there a way to fix it? You might recalibrate the monitor to work correctly while on its side, but then the picture would be equally distorted when you turn the monitor standing upright. Hardly useful... > 3. Is it harmful to the monitor to use it on its side? I don't think so. There are no moving parts inside it. The ventilation of the monitor may not work at its best, though. Don't let it get abnormally warm.
davidsen@sixhub.UUCP (Wm E. Davidsen Jr) (03/31/91)
In article <91087.155337REIDMP@MAINE.BITNET> REIDMP@MAINE.BITNET (Reid M. Pinchback) writes: | 1. What causes the colour distortion? | 2. Is there a way to fix it? One possible cause is a change in the magnetic field near the monitor, particularly if you run near the CPU or another monitor. Use of the degaussing control *may* help this. | 3. Is it harmful to the monitor to use it on its side? Monitors depend on convection cooling, and convection depends on gravity. I would be very careful of running a monitor on its side unless the vendor was contacted and said it was okay. Reason: heat rises, and I bet the cooling slots are in the top rather than the side. Addition of a fan, should you decide to do so, will probably cause more color distortion. There are monitors designed to be used either way, but you could kill your monitor and warantee in one stroke by running some monitors on the side. So: - call the manufacturer - if you try it watch the temp closely - if it runs hotter on the side it will have a shortened life - a fan would probably help, might cause problems. That still kind of leaves you on your own, but you understand the problems. Other than heat there's no reason why *most* monitors won't run in any position. I believe the space program noted that convection cooling does work worth beans with the gravity off, and that several computer failures were cause by just that. I don't have a NASA admission of it, though. -- bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen) sysop *IX BBS and Public Access UNIX moderator of comp.binaries.ibm.pc and 80386 mailing list "Stupidity, like virtue, is its own reward" -me
antonyc@nntp-server.caltech.edu (Antony Chan) (03/31/91)
iisakkil@vipunen.hut.fi (Mika R Iisakkila) writes: >REIDMP@MAINE.BITNET (Reid M. Pinchback) writes: >> When I set the VGA monitor on its side, there is a strange distortion of >> colour. >> 1. What causes the colour distortion? > It's the magnetic field of the Earth. The VGA pixels are so >close to each other, that this weak magnetic field is enough to make >electron beams to land on wrong pixels (=phosphor dots of wrong >colour). The monitor contains numerous magnets, which are adjusted >to compensate for the magnetic field. The calibration has of course >been made to work in the normal position of the monitor. Actually, if >you took your monitor to somewhere on the southern hemiglobe (sp?), >say Australia, the colours would be distorted while the monitor is >standing normally on the table! this explaination doesnt quite sound right to me. please dont flame, 'cause im not claiming to be an authority or anything, but... unless you're real close to the earth's magnetic poles, the magnetic field lines are close to parallel to the surface of the earth (running north to south). what this would imply is that the earth's magnetic field would affect the monitor based on whether the screen is facing north, south, east, or west, as opposed to which side it is resting on. to corroborate this, i cite the following: we had a big screen tv that had buttons in it that you were supposed to change if you ever rotated the tv (they were labelled N,NE,E,SE i believe) and i just turned my monitor (nec 3d) sideways and didnt notice a color distortion. as to why the color *does* distort: perhaps something in the monitor is loose (unlikely) maybe something nearby has a significant magnetic field that causes the distortion maybe gravity is pulling the electrons down to hit the wrong dots :) >> 2. Is there a way to fix it? > You might recalibrate the monitor to work correctly while on >its side, but then the picture would be equally distorted when you >turn the monitor standing upright. Hardly useful... >> 3. Is it harmful to the monitor to use it on its side? > I don't think so. There are no moving parts inside it. The >ventilation of the monitor may not work at its best, though. Don't let >it get abnormally warm.
akm@geriatrix.cs.uoregon.edu (Anant Kartik Mithal) (03/31/91)
In article <1991Mar31.052527.9958@nntp-server.caltech.edu> antonyc@nntp-server.caltech.edu (Antony Chan) writes: >iisakkil@vipunen.hut.fi (Mika R Iisakkila) writes: >this explaination doesnt quite sound right to me. >maybe gravity is pulling the electrons down to hit the wrong dots :) Actually, that's not likely. Electrons are negatively charged, so gravity would pull (push) them upwards. :-) :-) Sorry, I couldn't help it... kartik -- Anant Kartik Mithal akm@cs.uoregon.edu Research Assistant, (503)346-4408 (msgs) Department of Computer Science, (503)346-3989 (direct) University of Oregon, Eugene, OR 97403-1202
antonyc@nntp-server.caltech.edu (Antony Chan) (04/01/91)
antonyc@nntp-server.caltech.edu (Antony Chan) writes: >iisakkil@vipunen.hut.fi (Mika R Iisakkila) writes: >>REIDMP@MAINE.BITNET (Reid M. Pinchback) writes: >>> When I set the VGA monitor on its side, there is a strange distortion of >>> colour. >>> 1. What causes the colour distortion? >> It's the magnetic field of the Earth. The VGA pixels are so >>close to each other, that this weak magnetic field is enough to make >>electron beams to land on wrong pixels (=phosphor dots of wrong >>colour). The monitor contains numerous magnets, which are adjusted >>to compensate for the magnetic field. The calibration has of course >>been made to work in the normal position of the monitor. Actually, if >>you took your monitor to somewhere on the southern hemiglobe (sp?), >>say Australia, the colours would be distorted while the monitor is >>standing normally on the table! after a bit more thought, it seems to me that the only way turning a monitor on its side could be affected by the earth's magnetic field is if the dots have looser tolerances in the up-down direction than the left-right direction. i.e. if the electron goes too high or too low, it's not as bad as if they go too far right or left. since in a uniform field the electron will try to circle the magnetic field lines, in its normal orientation the beam will be either slightly to high or too low depending on which way its facing. on its side the beam will also either be slightly too high or too low, but this translates into too far left or right to the screen. ascii graphics follow: --------------------- | ^ | ----------------------- (mag fld lines) | | | ^ | --------->---- | | | | --------->---- ---| | | too high or low | --------->---- | | | | | --------->---- | | too far left or | | v | --------->---- ---| right | ----------------------- | | | | | | ------------ | v | (this one is the monitor --------------------- you're looking at now, and north is to your right) actually, i have only considered electron beams heading either straight north/south (no effect from earth's mag. field) and straight east/west (bends up/down). anything else involves a helix that is too much for me to think about during spring break. oh, and that australia thing just can't be right. it would only make a difference if you considered gravitational effects. (everyone knows that australians stand on their heads) :)
dd2x+@andrew.cmu.edu (David Eugene Dwiggins) (04/01/91)
Actually, the problem should correct itself after the monitor degausses itself several times. Rainbow colors are common after moving monitors around. David
edhall@rand.org (Ed Hall) (04/02/91)
I'm amazed at all the half-baked answers people have given to this one. Perhaps they all were written in honor of the day... :-) Yup, the problem is caused by the Earth. Nope, it has nothing at all to do with the Earth's magnetic field. Yup, it has to do with gravity. Nope, it has nothing to do with the effect of gravity on electrons. And degaussing won't help things a bit. The geometry between the electron gun(s) and the screen must be vary carefully aligned; generally this is done by "warping" the electron beam(s) with small magnets rather than actually moving the parts involved. Gravity makes a small but significant difference in the positions of the elements of the electron gun(s); this is compensated for in the positioning of the magnets. If you turn the tube, the effect of gravity changes. If you wanted to (and knew how), you could re-align things so that the change is corrected for. But then, of course, the tube wouldn't work right when put back into its original position. -Ed Hall edhall@rand.org