Color TV: Newsletter Challenge (11/15/05)

All (CRT) picture tubes have a metal screen called the 'shadow mask' mounted just behind the inside surface of the tube. Besides providing the focus aperture for the three color guns, the mask's job is to nullify the effect of the Earth's magnetic field on the electrons flying through it. If the mask itself becomes magnetized, the color purity and focus of the image get screwed up. With the exception of only the newest plasma sets and LED screens, every computer monitor, TV set and Video Game has a CRT which is susceptible to these localized magnetic fields. The 'shadow mask' needs to be demagnetized using a 'degaussing coil', which is nothing more than a 110 volt 60 cycle AC coil inside a safe plastic shield (i.e: insulating tape). This needs to be passed over the screen in order to repair the disruption to the mask. I wonder if an ordinary transformer could be used to the same effect?

Stole my thunder!

Sorry :-)

On my CRT I'm able to degauss by going into the monitor (compaq V 1000) menu and selecting "degauss". This is the only reason I know the answer.

a normal transformer wouldn't work because of the laminations that create a magnetic short circuit. I would either use a ferrite bar-core coil, or break apart half of the laminations to force some of the magnetic field through the tv. Look up something called hysteresis if you want to learn more about degaussing.

Turn off the TV and tell them to get back to work. Seriously, I have no idea.

Well, all I can say that when I did this as a kid (to our NEW color TV, no less), I was playing with a big magnet from our electric lawn mower (about 3 or 4 inches in diameter, about 1/3 inch thick). I was freaking out trying to get the green color to leave the center of the TV (where I put the magnet). My solution? I broke the magnet in half (I wanted to do that anyway!) and "pulled" the color back to the edges by moving the two pieces in opposite directions. It worked pretty well, but I suspect the TV degaussed itself later (or someone knew to do it), because after a few days you couldn't see any leftover spots of saturation.
Now kids... don't try this at home!

When this happened to me, I degaussed by holding the magnet in the area where the "mishap" had occured, then, while passing it in a circle in a plane parallel to the TV screen, I moved the magnet away from the screen. I did this while the TV was on, so I could see what happened to the color distortion. The first go, it didn't "fix" it. So, keeping the magnet moving in that little circle, I came back in toward the screen, and backed back out again. This did what a degaussing coil does (move the magnetic domains around, reorienting them, and, by lowering the field strength gradually, leave them in a random order: demagnetizing the metal).

Ah yes, those were fun times! I think my parents knew I was going to end up in science around the time I started making stinky stuff with my brother's chemistry set.

Just throw away the Old TV and buy a new Plasma TV. Everyone will be happy. Problem Solved!. And your daughter will say, "Daddy I Love You"..