De-gaussing a television?
Discussion
I have recently noticed the top corner of my CRT TV has begin to show a blue colour when it is supposed to be displaying red. Apprently this is because the TV has become magnetised?
Does anyone know how I can fix it? The TV is still under guarantee but it would be a nightmare to send it back.
I am fairly sure the TV is 75Hz so I suppose I would need something that operates at this frequency.
Any ideas?
Does anyone know how I can fix it? The TV is still under guarantee but it would be a nightmare to send it back.
I am fairly sure the TV is 75Hz so I suppose I would need something that operates at this frequency.
Any ideas?
My TV did this after a nearby leccy substation was hit by lightning. (TV was plugged in and on standby) advice from manufacturer was to turn off completely and unplug from wall, leave it for a while (forget how long - poss an hour or so) then plug in and turn on. I was dubious, but it did actually work.
I always used to leave the tv on standby, but apparently thats not a good idea.
I always used to leave the tv on standby, but apparently thats not a good idea.
esselte said:
Is there anything on the menu on the TV that will do it?Lots of PC monitors have this .
Maybe, but I think TVs degauss themselves everytime you turn them on which doesn't seem to be working. Someone on google groups seems to think you can do it with an electric Razor! I'm a bit worried that with my TV being an unusual frequecy it will make it worse though.
May have to get a proffesional, hope they do home visits as it's sure as hell not going to fit in my car.
esselte said:
Is there anything on the menu on the TV that will do it?Lots of PC monitors have this .
Ah - my favourite button on those big old Sun
workstation monitors - technically known as the
"Wibbly Wobbly Button" - press it, the whole monitor
emits a resounding thud, and the image on every other
screen within 6 feet goes..er...wibbly wobbly as well.
Flat panels are nowhere near as much fun, and don't
keep you warm in the winter.
dieseljohn said:
Is there anything on the menu on the TV that will do it?Lots of PC monitors have this .
Maybe, but I think TVs degauss themselves everytime you turn them on which doesn't seem to be working. Someone on google groups seems to think you can do it with an electric Razor! I'm a bit worried that with my TV being an unusual frequecy it will make it worse though.
May have to get a proffesional, hope they do home visits as it's sure as hell not going to fit in my car.
I had the same problem with a 32in widescreen, was fixed in my home in about 10 seconds.
eharding said:
Is there anything on the menu on the TV that will do it?Lots of PC monitors have this .
Ah - my favourite button on those big old Sun
workstation monitors - technically known as the
"Wibbly Wobbly Button" - press it, the whole monitor
emits a resounding thud, and the image on every other
screen within 6 feet goes..er...wibbly wobbly as well.
Flat panels are nowhere near as much fun, and don't
keep you warm in the winter.
Yeah it's a cracking thud on the 21"ers isn't it.
GreenV8S said:
Don't CRTs normally de-gauss themselves spontaneously when switched on from cold? Perhaps the degaussing circuit has failed. Or perhaps the tube itself is simply failing.
I bloody hope not I've only had it two weeks!
I should really send it back but I got it from Amazon who are not exactly the best for returns and it was a total mission getting it delivered in the first place.
esselte said:
esselte said:
Is there anything on the menu on the TV that will do it?Lots of PC monitors have this .
Ah - my favourite button on those big old Sun
workstation monitors - technically known as the
"Wibbly Wobbly Button" - press it, the whole monitor
emits a resounding thud, and the image on every other
screen within 6 feet goes..er...wibbly wobbly as well.
Flat panels are nowhere near as much fun, and don't
keep you warm in the winter.
Yeah it's a cracking thud on the 21"ers isn't it.
Just did mine to wake the office up a bit 
dieseljohn said:
I have recently noticed the top corner of my CRT TV has begin to show a blue colour when it is supposed to be displaying red. Apparently this is because the TV has become magnetised?
Does anyone know how I can fix it? The TV is still under guarantee but it would be a nightmare to send it back.
I am fairly sure the TV is 75Hz so I suppose I would need something that operates at this frequency.
Any ideas?
As others have said, most new CRT based TV's auto degauss. The purpose of this is to keep the colours (purity) uniform across the whole screen. Behind the actual CRT there will be a lot of earth braiding which also holds permanent magnets around the tube. These magnets 'help' with keeping the purity correct, i.e. no blotches or colour.
When sets develop purity problems, it is normally caused by placing magnetic sources too near the set - typically fooking great loudspeakers are normally the cause. That is why all computer speakers are shielded. First thing is to check that there are no speakers or devices which emit large amounts of electromagnetism like a large trasnformer or a power amplifier - I am not talking your average hifi amp, but more like a PA/disco amp; the terroidal transformers in there would screw your picture up nicely
If there is anything near like that, move it away. To deguass is very simple and you can do it yourself. I have never heard of anyone using an electric razor but thinking about it a proper deguassing tool looks alsmost identical to a razor except it doesn't have any clippers
An electric razor does have a coil for the motor so it may work. What you are trying to achieve here is to place a powerful electric field onto the screen and drag the colours around until they are fully blended. You may also be able to deguass with a permanent magnet, but in the trade we normally use an electromagnet because you don't want to end up magnetising all your tools 
You need to feed the tv a source of pure white as a test picture so you can observe and see when the colour gets corrected. Easiest way is to open a new paint picture on your PC paint the whole picture white and save it. Then display it as a picture slideshow on puase and output the picture via your pc's video out if you have one.
Then all you do is place your deguassing tool in the middle of the screen, with the TV on and no picture displayed, just the white background as above, and slowly start to pass the electromagnet round and round, starting from the middle and moving into larger circles. Always go in the same direction, and slowly make the circle bigger until you end up at the outside of the screen. For a 4:3 set it was easy as you are going in a perfect circle; however for a 16:9 widescreen it will require patience as you are effectively drawing an oval
and I have never done a widescreen deguass You will notice the colours go 'a bit mental' but they should settle down after you have passed over them.
If you require any further info drop me a line
damn simon beat me to it.
As others mentioned - there should be a cable running around the tube at the edge of the screen - this effectively degausses the tube every time you switch on. This mihgt have died - or maybe you just stuck a big speaker too close to the tv.
MAgnet in circles from centre to edge whilst slowly moving away from the screen sorts it.
Good luck!
As others mentioned - there should be a cable running around the tube at the edge of the screen - this effectively degausses the tube every time you switch on. This mihgt have died - or maybe you just stuck a big speaker too close to the tv.
MAgnet in circles from centre to edge whilst slowly moving away from the screen sorts it.
Good luck!
ultimasimon said:
Loads of stuff
Thanks a lot for the info mate.
I am very careful to keep magnets away from the TV, but perhaps the lodger did something he's not admiting or it may have come like that.
If I have a go at it with a magnet or a razor or something and screw it up could I make matters worse?
vixpy1 said:
The convergence could have wondered off..
Have it looked at
Ah another 'old hands' technician
Convergence is the static raster. If the convergence was out on one colour then you would see the picture distorting. From all accounts the picture is still square but just another colour. This is a purity problem and is caused by electromagnetic interference or by failing static convergence magnets. On modern sets convergence is electronically /digitally programmed and very rarely goes out, but on the old sets if it was set up by an idiot when manufacturered this would be very possible. Sadly most of the sets which did this from new were not scrutinised properly by QA, such names include Bush, Amstrad, Decca and Fidelity. The japs very rarely get this wrong and this is engineered not to happen. And we wonder why we didn't end up being world leaders in consumer electronics
dieseljohn said:
Loads of stuff
Thanks a lot for the info mate.
I am very careful to keep magnets away from the TV, but perhaps the lodger did something he's not admiting or it may have come like that.
If I have a go at it with a magnet or a razor or something and screw it up could I make matters worse?
No, go find a big
off magnet and try as said above. Because the set has permanent magnets strapped around the tube, these should recover it. Just keep the magnet moving and do not 'soak' the tube, in other words you should be able to see the colours literally getting dragged around the screen with the magnet. The worst case senario is to ring the shop and send it back. Amazon are not techies, they are in the business of box moving
They also have a duty to replace it under the sale of goods act so you ared within your rights...just don't tell them you have deguassed it, they may use that as an excuse not to exchange it but you are only doing what a trained tech would do. It does not do any permanent damage it is the correct procedure for the fault
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