Errr.... Sorry to state the obvious but this is a 14" CRT. It's the sort of thing that's hardly worth repairing. Used ones are available from £10 - £0.
If you know where you can get £10 for them, I'll spilt it 50/50
As you say, totally worthless these days - unless the set is of some use to you, as it may be to the OP?. But it's not really something you'd want to pay to get repaired.
It's about the strength of the field. I didn't think the normal degaussing field would be enough to permanently magnetise the shadow mask if interrupted without being allowed to decay. I still find it surprising, but not impossible.
Nothing at all surprising about it - applying DC to a coil produces a permanent magnet - back to primary school science for that.
Nothing at all surprising about it - applying DC to a coil produces a permanent magnet - back to primary school science for that.
Oh, good grief. You just can't help yourself, can you? I have a degree in physics. I think we can safely assume I know how that works. And no, it doesn't produce a permanent magnet. It produces a temporary magnet, as long as the current is flowing, and the strength of that field can be calculated using long-established equations.
I know that the internal degaussing coil on a TV may take many attempts to shift magnetism induced by subjecting it to a powerful external field, and that sometimes it won't succeed and a more powerful external device may be needed. So I had assumed (perhaps wrongly) that a momentary field induced by "degaussus-interruptus" would not have been able to mangle the screen as described in the OP. I'm still not entirely convinced that it did.
Oh, good grief. You just can't help yourself, can you? I have a degree in physics. I think we can safely assume I know how that works. And no, it doesn't produce a permanent magnet. It produces a temporary magnet, as long as the current is flowing, and the strength of that field can be calculated using long-established equations.
Considering you are incorrect about this, we obviously can't assume you know how it works - and if you really have a degree in physics I'm stunned by your lack of understanding of degaussing systems.
Permanent magnets can be, and often are, made by a DC solenoid. Temporary ones (electro-magnets) need special soft cores in order not to become permanent. The permanent magnets created in this way aren't as strong as when the current is actually flowing through the coil though.
I know that the internal degaussing coil on a TV may take many attempts to shift magnetism induced by subjecting it to a powerful external field, and that sometimes it won't succeed and a more powerful external device may be needed.
The internal degaussing field is actually more powerful than external ones - such as engineers use for external degaussing. Probably because it's actually wound round the outside of the tube?.
So I had assumed (perhaps wrongly) that a momentary field induced by "degaussus-interruptus" would not have been able to mangle the screen as described in the OP.
Again it's simply DC creating a permanent magnet.
I'm still not entirely convinced that it did.
And you claim to have a degree in physics?, it's a simple concept, like I said before, of primary school level.
But any TV engineer from the CRT days could tell you instantly what was wrong from the OP's initial report on here - any who couldn't has never mended CRT TV's.
njp, go and get your degaus wand find a crt set, energise then de-energise close to the screen and see what a mess you are left with.
I used to make screwdrivers magnetic by inserting the shaft in a coil of about one hundred turns the putting 12volts through the coil for a second or two, worked a treat.
I used to make screwdrivers magnetic by inserting the shaft in a coil of about one hundred turns the putting 12volts through the coil for a second or two, worked a treat.
We did it at primary school, but using nails and probably only 6V
My daughter did it as well, not so many years ago.
In order to stop the nail becoming a permanent magnet (to use as an electro-magnet) you can heat it to red heat, then let it slowly cool down. This 'softens' the steel to some degree, and prevents ot becoming a permanent magnet.
Obviously at primary school the teachers used to do that part
Permanent magnets can be, and often are, made by a DC solenoid.
Completely irrelevant to your "applying DC to a coil produces a permanent magnet". No, it doesn't.
The internal degaussing field is actually more powerful than external ones - such as engineers use for external degaussing. Probably because it's actually wound round the outside of the tube?.
In which case, why are external degaussing coils sometimes used in cases where the problem cannot be solved by the internal degaussing?
And you claim to have a degree in physics?, it's a simple concept, like I said before, of primary school level.
The concepts are not the issue. The magnitude of the effects is. But then, you were never good on magnitudes, as we saw in your hilarious failure to understand basic thermodynamics in an earlier thread.
Completely irrelevant to your "applying DC to a coil produces a permanent magnet". No, it doesn't.
Of course it does - perhaps I should have added "for the magnetically susceptible material inside it" - but it was so blindingly obvious I didn't bother.
In which case, why are external degaussing coils sometimes used in cases where the problem cannot be solved by the internal degaussing?
Very often because the posistor is already hot, and you can't wait an hour it two for it to cool down.
But I've done a number of cases (in the later years of CRT) where repeated external degaussing wouldn't cure it.
In each case the cure was to remove the back of the set and freeze the posistor to within an inch of it's life, thus restoring it to it's initial cold condition.
But again, you're trying to make points about something you don't have the slightest experience or understanding of.
The concepts are not the issue. The magnitude of the effects is. But then, you were never good on magnitudes, as we saw in your hilarious failure to understand basic thermodynamics in an earlier thread.
We seemed to agree to disagree there, and your blindingly poor understanding of physics in this thread means I'm even less convinced than before by your previous arguments - but let's not go there again.
Of course it does - perhaps I should have added "for the magnetically susceptible material inside it" - but it was so blindingly obvious I didn't bother.
The devil is in the detail. You aren't good on detail.
but again, you're trying to make points about something you don't have the slightest experience or understanding of.
I would have willingly deferred to your greater experience in the one small area where you appear to have some genuine knowledge, had you not decided to be so aggressive in your initial response. As it is, seeing if I could make your head explode turned out to be more fun.
We seemed to agree to disagree there, and your blindingly poor understanding of physics in this thread means I'm even less convinced than before by your previous arguments - but let's not go there again.
Where have I misunderstood any of the physics? This is about the magnitude of the effects.
But given your failure to understand anything beyond vague hand-waving qualitative arguments in the other thread, I concede that you are at least consistent in your approach.
I would have willingly deferred to your greater experience in the one small area where you appear to have some genuine knowledge, had you not decided to be so aggressive in your initial response. As it is, seeing if I could make your head explode turned out to be more fun.
I think it might have been your aggressive response to Nigel's initial comment that might have done it.
Comments
If you know where you can get £10 for them, I'll spilt it 50/50
As you say, totally worthless these days - unless the set is of some use to you, as it may be to the OP?. But it's not really something you'd want to pay to get repaired.
Nothing at all surprising about it - applying DC to a coil produces a permanent magnet - back to primary school science for that.
I know that the internal degaussing coil on a TV may take many attempts to shift magnetism induced by subjecting it to a powerful external field, and that sometimes it won't succeed and a more powerful external device may be needed. So I had assumed (perhaps wrongly) that a momentary field induced by "degaussus-interruptus" would not have been able to mangle the screen as described in the OP. I'm still not entirely convinced that it did.
Considering you are incorrect about this, we obviously can't assume you know how it works - and if you really have a degree in physics I'm stunned by your lack of understanding of degaussing systems.
Permanent magnets can be, and often are, made by a DC solenoid. Temporary ones (electro-magnets) need special soft cores in order not to become permanent. The permanent magnets created in this way aren't as strong as when the current is actually flowing through the coil though.
A little something for you to read:
http://www.nuffieldfoundation.org/practical-physics/making-permanent-magnet
The internal degaussing field is actually more powerful than external ones - such as engineers use for external degaussing. Probably because it's actually wound round the outside of the tube?.
Again it's simply DC creating a permanent magnet.
And you claim to have a degree in physics?, it's a simple concept, like I said before, of primary school level.
But any TV engineer from the CRT days could tell you instantly what was wrong from the OP's initial report on here - any who couldn't has never mended CRT TV's.
I used to make screwdrivers magnetic by inserting the shaft in a coil of about one hundred turns the putting 12volts through the coil for a second or two, worked a treat.
We did it at primary school, but using nails and probably only 6V
My daughter did it as well, not so many years ago.
In order to stop the nail becoming a permanent magnet (to use as an electro-magnet) you can heat it to red heat, then let it slowly cool down. This 'softens' the steel to some degree, and prevents ot becoming a permanent magnet.
Obviously at primary school the teachers used to do that part
In which case, why are external degaussing coils sometimes used in cases where the problem cannot be solved by the internal degaussing?
The concepts are not the issue. The magnitude of the effects is. But then, you were never good on magnitudes, as we saw in your hilarious failure to understand basic thermodynamics in an earlier thread.
Of course it does - perhaps I should have added "for the magnetically susceptible material inside it" - but it was so blindingly obvious I didn't bother.
Very often because the posistor is already hot, and you can't wait an hour it two for it to cool down.
But I've done a number of cases (in the later years of CRT) where repeated external degaussing wouldn't cure it.
In each case the cure was to remove the back of the set and freeze the posistor to within an inch of it's life, thus restoring it to it's initial cold condition.
But again, you're trying to make points about something you don't have the slightest experience or understanding of.
We seemed to agree to disagree there, and your blindingly poor understanding of physics in this thread means I'm even less convinced than before by your previous arguments - but let's not go there again.
I would have willingly deferred to your greater experience in the one small area where you appear to have some genuine knowledge, had you not decided to be so aggressive in your initial response. As it is, seeing if I could make your head explode turned out to be more fun.
Where have I misunderstood any of the physics? This is about the magnitude of the effects.
But given your failure to understand anything beyond vague hand-waving qualitative arguments in the other thread, I concede that you are at least consistent in your approach.
You can probably find one in the classifieds for free or close to it..less effort then hauling it away as trash..not worth bothering with anymore.
I think it might have been your aggressive response to Nigel's initial comment that might have done it.
http://ademdjemil.co.uk/blog/2007/08/how-to-degauss-a-tv