• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

In DEAP TV trouble. Please help me.

Status
Not open for further replies.

Electric Rain

New Member
I have a very bad problem. My TV is magnetized. It happened when I went to move my CD player. My CD player was sitting on top of my TV. I knew this would be ok and that the built-in speakers would not magnitize the TV because they were too far away from the TV. But, I went to move it, and I lifted it up of my TV, and kind of, passed in front of the TV briefly. So the magnets on the speakers on both sides of my CD player resulted in the left and right sides of my TV being magnetized. And the big problem is, it's the main living room TV. I've been looking up some articles about this, and they say that TVs and monitors have "degaussing coil" built in that will automatically demagnetize them over a period of time. How long would that time be? I also read something that says that you can demagnetize TV's with "a magnetic field that fluctuates back and forth and gradually diminishes to zero." Can I buy/build something like that? I read this article: http://www.crosbycomms.co.uk/Learning/tv.htm Can someone please help me?
 

Sebi

Active Member
Don't worry. The degaussing coil in TV not working when You switched on and off only with remote controller. Just switch off with mechanical switch (if existiert) or disconnect from mains, wait about 30min, and switch on. If the first degaussing procedure not enough (too strong magnetic field on screen) repeat twice.
When no success, the PTC in TV-degaussing circuit damaged, change it.(cheap 3pin part)
Also possible degaussing with external coil, but this problem always occur, when something change in our environment.
 

Dean Huster

Well-Known Member
Degaussing

This very item came up as a question in my "Q & A" column in the final issue of Poptronics magazine. Since the mag is now defunct after years of publication, I'll reprint what I wrote here:


Eventually, most people, especially the curious ones, discover in a bad way the adorable Etch-a-Sketch qualities of a color TV or computer monitor when you start playing with permanent magnets around them. The electron beams within the picture tube are normally deflected by the magnetic fields of the deflection yoke around the neck of the tube. The permanent magnets have magnetized the front of the shadow mask area of the tube and pulls the otherwise perfectly-aligned electron beam off-course so that they don't hit the colors they're supposed to hit if they hit any at all.

It may be that the spot will go away by itself after several cycles of turning the TV off and on. Every color TV has a degaussing coil around the picture tube that when first turned on, has a decreasing-voltage ac signal that demagnetizes the picture tube to keep the colors pure. Normal moving of the TV, the earth's magnetic field and playing with magnets cause these anomalies. A permanent magnet that goofs things up is a little more difficult for this weak degaussing field to "erase", but it may eventually go away, especially if the sot is near the edge. The TV must be turned off and remain off for at least fifteen minutes before turning it back on or the coil won't go through its cycle. It's often controlled by a thermistor in series with it across the ac line and if the thermistor is hot (as it is with the set running), it's a high resistance and the coil will have no field. The thermistor has to cool down first.

Some televisions or monitors may have a manually-activated degaussing button you can press repeatedly to clear up the problem. If the splotches don't go away on their own through these slightly extended efforts, you'll have to get more drastic.

You can buy a degaussing coil that may do the trick. Or you can hunt around for someone who has one of the old bulk tape erasers. Those work even better because they have a stronger field. The idea is that you have an ac signal that demagnetizes the picture tube. Plug the degaussing coil into an outlet and slowly move it in front of the face of the television, concentrating around the area around the offending spots. The SLOWLY bring the coil far away from the tube before turning it off so that you don't get a final magnetic spike that will remagnetize the tube.

You have to be more careful with the bulk tape eraser. Again, turn it on away from the tube and then bring it close enough that its field affects the picture strongly, moving it slowly around near the face of the tube. This field is strong enough that you don't want to get too close to the tube so that you don't wreck the shadow mask structure. Then pull the eraser back slowly until you're several feet away from the TV before you turn it off. If it gets turned off too close to the tube, it can remagnetize the tube in funny spots and you'll have to do it all over again. I didn't see a degaussing coil in the big Radio Shack catalog. MCM Electronics or Dalbani may have one since they specialize more in consumer product repair. I've even seen them in the past at discount stores that are homebased in Bentonville, Arkansas.

Be very, very careful with rare earth permanent magnets, such as those you remove from computer hard drives, when you're around picture tubes. Two of them snapping together can pinch a blood blister onto your fingers. That'll go away. One of them can do permanent damage to a picture tube.

www.mcmelectronics.com 800-543-4330
www.dalbani.com 800-325-2264


Dean
 

Electric Rain

New Member
... :oops: Umm... I guess the degaussing coil really does work. :oops: It's fixed. Thanks for all of your help you guys. And Sebi, before I even got your post, I unplugged it for a bit 'cause I also read that it helps. It did. Flawless. Good as new... sorry for troubling you guys with this. But I will remember this thread so I can come back if it happens agian and the coil doesn't work. Again, thanks. :) :wink:
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top