Not a definitive answer by any means Dave but I hope it's the same for you and so puts your mind at rest.
1) When I helped out in the IT department in Sixth Form the screwdrivers used had magnetic tips on. However, they were used on the screens all the time. In fact, on lazy Friday afternoons there was a competition to draw the most swirly pictures on the screen using the said screwdriver but I wasn't a party in this obviously.
::ahem
2) Picture this. Get a new DVD player which you've just hooked up to some speakers. You then decide, in a moment of madness to place the speakers on top of the TV. You look at the TV and discover, with quite a bit more than mild panic that the top half of the screen is a rather fetching shade of green. Needless to say, you remove the offending items, switch the TV off and then on again and all was fine.
I hope it's the same for you.
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Adam
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switch the TV off and then on again and all was fine. I hope it's the same for you.
Thanks for that Adam. However the torch was placed by the telly last night. At the time the picture wasn't affected, but tonight it's a different story.
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DD. Try leaving it off 24/48hrs. should be time enough for tube to power down..then once switched back on may possibly be rectified..Unfortunatly. the longer the magnet is close to tube
the less chance of recovery
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Steve
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Ps DD.forgot to mention. Adam was right. and point I missed. if you cannot clear. it will need Degausing (not certain I spelt that right)
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Steve
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With the most common TV, there is a sheet of precision perforated metal that is called a shadow mask just inside back from the front glass. The beam, focused from the other end of the tube, goes through the holes to strike the correct colour phosphor/s. However, magnets deflect electron beams, (as do electrostatic fields) hence your wrong colours on the picture.
TV sets have a coil round the tube (or used to) in the vicinity of the mask, who's purpose is to demagnetise the mask at switch-off, provided the magnetism is the usual weak stuff. Perminent magnets can put in too strong a magnetism for this to work -- it needs more power.
What you need is your own (degaussing)coil. For instance, mains current running through a coil that is moved across the screen front over all its parts and then taken away while still switched on, before switching it off. You may be able to borrow one from a TV service place.
Otherwise, how venturesome do you feel? Myself I would make one using a drum of single core wire (if I had nothing else) and put a large lamp or even an electric fire in series to limit the current. You only need it on for a few seconds and must take care that the plastic wire does not get too hot -- and melt! And of course, take the usual precautions against electric shock.
The degausing coil 'quality' factor is amp-turns. So a 1 bar (4 amps) fire as ballast will need less turns than a 100 watt (0.4 amps)lamp. And if the coil has enough turns the current will be self limiting and you don't need the lamp/fire. With a 'good' coil you should be able to feel it rattle a screwdriver inserted inside it.
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Your TV will be back to normal afterwards.
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Buzbee is mostly right.
1/ you might not have a shadow mask if its a trinitron screen.
2/ TV sets (and monitors) mostly auto degauss at switch on, however to do this they need have been left off for a while to cool down. Note Switch on - not re activated from standby. It may take several attempts to completely re neutralise (degauss) the screen, so this means in practise several days.
3/ While it may be great fun to make up your own degaussing coil Its not for an amateur, and its use (there is a technique - its a bit like waving a magic wand in circles slowly pulling it away from the tube) takes practise. You could end up inducing more stray magnetism into the tube.
So Turn it off (not standby) at nights for a week. I bet it will slowly improve, If not then call out a TV repair man who can plug in and wave his magic wand.
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Do you have a tape head demagnetiser?
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Use it up : Wear it out : Make do : Do without
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Not big enough - too localised, a bulk tape eraser might do it tho.
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I have used 'E' cores (left open) from a transformer and the mains winding to create the field -- drop the voltage a bit if it gets hot too quickly. It has to be done quickly as it gets very hot due to the high current that flows and I purposely did not advocate this method for use by the novice. I have used it successfully a few times. As you say, it helps if you know what you are doing.
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Is the trinitron not just a shadowmask with rectangular holes?
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The some trinitrons are actually a series of vertical wires. You can sometimes see the bracing horizontal wire (or two) about 1/3 and 2/3 from the top. Give them a good tap and you can see the picture shimmer as the wires vibrate.
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The reason you let the set cool down before switching it on to try again is because the coil (round the tube) has a thermistor connected in series with it that heats up (just as you switch on) to cut off the coil current and so you have to wait for that to cool to get a current surge at switch-on again --- sort of 5-10 minutes perhaps. Whilst such attemps might eventually succeed, I will be surprised if just waiting a week has any benificial affect at all.
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Thanks everyone for their suggestions so far.
No, it's not a trinitron. It's a humble 14" portable (with teletext), made by a company called Tatung. It's approx 3 yrs old, and not worth a lot (##), but has some sentimental value as it was given to me as a present. I'm tempted to leave it be for a few days to see if it will degause itself. Failing that, I will ring the local tv shop for an estimate on having it demagnetised.
## I see new 14" portables with built in DVD players are now selling for around the £80 mark, so if I have to replace it, it's not going to break the bank. I'll just have to convince the person who bought it for me that it's knackered.
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It won't demagnetise itself. Simply follow the instructions here switching it on and off, repeat after 20 mins or so. 3-4 times and it should be fixed. You can hear if the degaussing function works by the big thump sound that the TV emits when you first turn it on.
I wouldn't try to unflux it yourself or build your own degausser, you'll end up bending the shadow mask or permanently magnetising it.
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If it's any help, I did this to my parents' TV many years ago at Christmas ( I put a magnetic toy on it ).
Ignoring the problem for a week or two did the trick, as it gradualy returned to normal.
Hope this works; it's free.
V
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Going back to one of Adski's original points, U have DVD 5.1 connected up to Tv, with the ".1" speaker sitting on top of the tv on its wee stand, as the instruction manual suggests.
Will this potentially give me problems? Its been there for coming up to a year (guess when I got it?!) but TV seems ok so far?
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It will be fine Bobby for a few reasons:
1) As you say, it's been a year
2) The manual suggest is
3) Don't know how big the stand is but I have a computer speaker on top of monitor (moved when tidying up) and it's fine
4) I'm no T.V. expert but I'm guessing any effects would be pretty much instantaneous
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Adam
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Going back to one of Adski's original points, U have DVD 5.1 connected up to Tv, with the ".1" speaker sitting on top of the tv on its wee stand, as the instruction manual suggests. Will this potentially give me problems? Its been there for coming up to a year (guess when I got it?!) but TV seems ok so far?
Most speakers sold in conjunction with home cinema are magnetically shielded. I've got a dirty great pair of three-way floorstanders either side of my TV and the matching centre speaker (identical coils, just a smaller horizontal cabinet) placed within 1.5 inches of the bottom of the TV and no problems. If they weren't shielded I suspect I would have microwaved the cat within about 10 seconds of turning this lot on.
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Actually, a magnet should help to cure it. I recall that holding a magnet at the spot where the screen has discoloured, then making sweeping movements of magnet to edge of screen, should move discolouration away. Or am I talking about de-gauzing...or is that the same?
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Just to update things. Well after a couple of days of numerous turning on and off, along with turning it completely off the past couple of nights for 12 hour periods, the picture has not improved one bit.
The Simpsons made interesting viewing. Ever seen them in green?
Anyway, had a google tonight and found one or two interesting things to try.
One of which was to wave a plugged in soldering iron in front of the screen, starting in the middle and making a circular motion outwards until you're clear of the screen - didn't work. Aparantly a soldering iron has the same principles as an electromagnet.
Another was to wave the original magnet in front of the screen, again starting in the middle and circling outwards - this has improved the picture. Now only the top and bottom of the screen is still wrong.
I also found a site showing how to make my own degausser ( www.flickerdown.com/stewks/articles.php?articleId=...6 ) but before I go down this route I'll phone the local tv shop on Monday for an estimate. If it's only going to be £5 to £10, then it's not worth the bother (or risk) of electrocuting myself!!
Thanks for all your suggestions, btw.
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Just to further update this. Phoned a mate today who I was sure would have a degaussing coil as he used to repair TV's, Video's & all other things electronic as a hobby. He no longer has the coil because repairing anything electronic is a waste of time these days as we now live in a disposable world where replacing the faulty product is just as cheap as trying to repair it. He's thrown out most of his kit.
Anyway, phoned the local TV shop and they still have a degaussing coil "out the back somewhere". They're gonna do it for £10.
I'd totally forgotten about the TV card in the puter until now. So I'm currently watching Wheeler Dealers (BMW Tourer) whilst typing this. (Oops sorry, wrong thread)
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Had this a while ago - my little girl playing with a strong magnet. Nothing shifted it. Phoned a TV repairman mate - he told me to turn the TV upside down and give it a gentle shake.
Now I can tell you I instantly told him to go away. He laughed but insisted that I give it a try. Yeah, course will.
Off the phone I turned the telly upside down and gently shook it. Fully expecting it to be a wind up I switched it back on and was amazed when it was perfect.
When I saw him next, without saying a thing to him, he grinned and asked if the telly was alright? We then burst into laughter. (you had to be there) He new I thought it was a wind. up.
It worked though. Give it a try.
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