magnet damage to powerbook lcd

[Lt Major Burns]

i have a freind who's powerbook screen has some magnet damage to it. how do you fix this? on a CRT, i would degausss the monitor till it went, but i'm not sure how this is done on LCD, or even if it's possible. what fixes lcd magnet damage?

 

[lurk]

I did not even know that is was possible to damage a LCD magnetically, what are the symptoms since ti could very well be a different type of damage. Cause really I can only imagine something physically broken or stressed to result the a "gee this needs to be degaussed" image on a LCD.

 

[DeltaMac]

In a normal world, an LCD cannot be affected in any way by magnetic fields (and, of course, has no need for degaussing), and is unlikely to sustain any damage of any kind from a magnet - unless you drop the magnet on the screen and get physical damage the same as any hard object dropped on the screen.

That said, can you describe the effect on the screen? Maybe it's actually cracked?

 

[eric2006]

Is it like this?
http://www.apple.com/support/powerbook/displayprogram/

 

[giantslayer]

I use my laptop for research with NMR (Nuclear Magnetic Resonance) Spectroscopy, which uses a powerful superconducting magnetic of about 7 Tesla. After nearly six months of research, the side of my 17" laptop closest to the magnet has darkened significantly and the screen whistles at a high pitch. Could the supercon have caused the screen darkening?

 

[Satcomer]

I use my laptop for research with NMR (Nuclear Magnetic Resonance) Spectroscopy, which uses a powerful superconducting magnetic of about 7 Tesla. After nearly six months of research, the side of my 17" laptop closest to the magnet has darkened significantly and the screen whistles at a high pitch. Could the supercon have caused the screen darkening?

Absolutely YES. With any display you should have it magnetic free. I was wondering if it is new enough to have Applecare on it?

 

[icemanjc]

I found this, not sure if it is the reason, but it was quite interesting.

The question was "Can magnets effect LCD screens?"

Yes but not for the same reasons.

Ever hear of the "Hall Effect Sensor"?

If not, then this page will get you started:

http://en.wikipedia.org/wiki/Hall_effect_sensor

Hall effect devices are basicly transistors with a magneticly sensitive base lead while a normal transitor will have a wire connecting the base to the emmitter and collector junctions

However EVERY transistor and EVERY diode can be affected by magnetic fields, to some degree, this is why you take of your electronic watch when you get a CAT scan because the scanner has an enormous magnet in it

What happens is that in a hall effect device it is optimized to sense magnetic feild changes, and what happens is that when you bring the correct pole of a magnet into proximity of the hall effect device (transistor) it turns it on, when you turn the magnet around the other way, it will shut the hall effect transistor off again.

Now your LCD screen although the screen has mainly Liquid crystal semi conductors in it tends to respond to some degree in the same way mainly for 2 reasons.

Liquid crystals are EXTREMLEY sensitive to electric field changes, so you don't even need a magnet to see how sensitive they are. Try this; put a piece of "scotch magic brand" (tm 3M) tape (the kind you can write on) and stick it LIGHTLY onto the face of your LCD screen, leaving one end NOT stuck down so that you can pull it back off.

Whith the monitor UNPLUGGED and the VGA connector OFF rapidly pull the tape off at about a 45 degree angle away from the LCD screen.

You will see many of your LCD "pixels come to life"

That is just from non-contact static electricity.

Now if you were to take say, the magnet out of the magnetron in a microwave oven and pass it over a running LCD monitor you may induce enough magnetic pressure to short out the transistors and diodes in the Liquid crystal display (that is the first method of magnetic interaction -- I said there were 2 remember?)

The second method that the magnet will cause problems is for the same reason that motors spin.

If you MOVE a magnetic field across a conductor like a wire or a circuit trace (and there are 10's of thousands of circuit traces embedded in the LCD screen) then you will magnetically induce an electric potential on those conductors and circuit traces -- you might short stuff out by turning something on when something next to it should be off

Bottom line?

Don't do it

 

[giantslayer]

No, my laptop is a few years old. It seems like the supercon is causing my laptop to darken and whistle. So is there any way to fix it? Or if I must replace it, are there laptops more resistant to magnetic fields?

 

[djackmac]

http://www.powerbookmedic.com/ for a new LCD panel. If its a macbook, macbook pro, ibook or power book G4 15" or 17" its not too awfully hard of a job to do if you've ever replaced LCDs on laptops before. If its a PB G4 12", that is going to be a complete take apart and then some. Even for experienced Apple portable techs like myself this is a task and a half! If you are squeamish about doing this type of repair I believe powerbook medic will do it for a fair labor charge, or check out your local Apple authorized shop to install it for you.