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 Post subject: CRT tv and speakers proximity
PostPosted: Mar Sat 28, 2020 9:58 pm 
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Joined: Feb Fri 27, 2015 3:19 pm
Posts: 93
I have a CRT color television and two floor speakers that I like to place on both sides of the tv. Am I running any risks that the magnetic field of the speakers can alter or even damage to color control of the tv beyond recovery?


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sat 28, 2020 11:46 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Try it and see. You won't do any permanent damage.


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 1:45 am 
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Location: Sunbury, Ohio 43074
With the TV on, move the speakers closer and closer to the TV. If you see any color blotching or shading to start, the magnetic field of the speakers is having an effect on the CRT. I'd move them away if that occurs.

Short term, it won't hurt anything, as long as the TV's internal degaussing system is in working order. Long term, I suppose you *could* magnetize enough parts on the chassis to require manual degaussing at some point. Doubtful that any permanent damage could occur, if you have a TV serviceman's style external degaussing coil. Or can borrow one.

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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 2:30 am 
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Location: Belrose, NSW, Australia
I was a TV service field tech in the early colour days. Saw hundreds of HiFi speakers near TV's but never saw a problem.

Yes the TV's auto degaussing system should take care of it.

You would need to pull the driver out of the box and wipe its magnet across the screen to see any effect that the auto degaussing couldn't handle.
But an external degausser can even fix this extreme case.

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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 9:02 am 
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Joined: Feb Fri 27, 2015 3:19 pm
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I thank you both but, for all the magic of Google, I could not find a picture of the magnet. Can one of you describe what it looks like or better provide a picture of it?


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 10:38 am 
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Location: Sunbury, Ohio 43074
You mean a demagnetizer? Do a google search for “degaussing coil” without the quotes

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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 12:05 pm 
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Joined: Feb Fri 27, 2015 3:19 pm
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Ok Barry, thanks. I saw it. I thought that by magnet was meant one of the parts around the neck of the tube.


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 12:43 pm 
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Location: Sunbury, Ohio 43074
I think I see the source of confusion. irob mentioned "wiping the magnet over the face of the CRT" .... he was referring to wiping a SPEAKER magnet over the face of the CRT would possibly magnetize the CRT enough to require an external degaussing coil to fix it.

Color TV's with few exceptions had an internal demagnetizing system included, because stray magnetic fields could cause color distortion in the picture. Even moving the TV would cause this, and the internal degaussing system would clear it up every time you turned on the set.

Yes, the CRT does have some magnets, and some electromagnets and coils, around the neck of the tube, and sometimes in earlier sets even around the front, but those are what the set is designed for. External magnets, such as a stereo speaker, *could* cause color distortions that the set itself cannot deal with. The CRT also has magnets for color purity adjustment, among other things. Those are designed to minimize color distortion due to local magnetic fields (like from the chassis, other metal parts, the metal in the CRT, etc), and magnetic fields such as that of the earth itself once the TV has been put in its location in your home. Later designs had similar, but relied a lot more on the internal degaussing system to demagnetize the tube and keep the colors pure.

Anyway, bottom line as stated... speakers are not going to cause any permanent damage. If you move them close to the TV and the color gets all wonky, move them back a bit.

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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 1:15 pm 
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Joined: Feb Fri 27, 2015 3:19 pm
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Very good, thanks.
On another aspect of the thread, if the speakers' magnets are not parallel or perpendicular to the screen, their effect on the picture should even less likely to occur, am I correct? By the way, by placing them close to the tv I meant an inch or two between the set and the speakers because of space restrictions.


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 1:20 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
yes and no ... lol. :) .... It has to do with the magnetic field from any particular magnet, not the orientation of the physical magnet itself. Generally speaking it depends on the physical shape of the magnet as to how it's field eminates, so you'd have to know that to see if physical orientation of the speaker would make any difference.

I'd think that most of the magnetic field of a speaker magnet would be contained within the speaker driver structure, but of course there is some "leakage" if you will. How much, you can only tell by measuring with equipment no one has, or just looking at the TV while it's on, as you move the speaker closer.

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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 2:57 pm 
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Joined: Feb Fri 27, 2015 3:19 pm
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Ok, thanks.


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 3:08 pm 
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Joined: May Sun 07, 2017 11:35 am
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Location: Belrose, NSW, Australia
If you really want to check this thoroughly, put a flat red screen up on your TV (camera pointing at a red object, defocused?) and see if moving a speaker close to the screen has any effect. I suspect you won't see any. Even if you do, it will go away when you put the speaker back where it was.

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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 3:25 pm 
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Joined: Feb Fri 27, 2015 3:19 pm
Posts: 93
To irob 2345,
aside from the fact that I can't find a red screen, I am confused: which camera and which red dot are you referring to?


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Sun 29, 2020 10:42 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
irob was suggesting that IF you had a color TV camera, you could point it at a red screen and display that on your color TV. RED is the color that most easily shows impurity in your TV color display.

There are ways to make your color TV go all red, but you'd need alignment knowledge and possibly equipment to get it back, so don't. Just look for any color impurities in a normal program. If you can't see them that way, you probably won't notice any at all.

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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Mon 30, 2020 3:07 am 
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Location: Pewaukee, WI
If the set.is post 1980 it almost certainly has an inline gun CRT and I've always heard green was the default purity setup color on those... though honestly a solid screen of green or blue (nearly every VCR and most newer TVs used that as their no signal screen) should do as well as red for detecting purity issues.

Red was the preferred purity setup for deltagun color sets that were predominant prior to 1970 and we're gradually phased out into the 70s.


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Mon 30, 2020 10:00 am 
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Joined: Feb Fri 27, 2015 3:19 pm
Posts: 93
Thank you.


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Mon 30, 2020 1:46 pm 
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Joined: Feb Thu 28, 2019 7:48 pm
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Location: Lawrenceville, Illinois 62439
As I recall, the first time I saw shielded speakers (or was the shield in the TV?) was during the huge CRT wave in the late 80's or 90's. RCA's Dimensia line had matching 32", 35" TV, audio, etc. and the floor speakers were the same style as the TV, and in many homes, were placed directly next to the TV.
Back in the 60's 70's combination sets had the speakers built into the same cabinet within a foot or so of the picture tube, not an issue.
Yes, agree to just try it.
Dan


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 Post subject: Re: CRT tv and speakers proximity
PostPosted: Mar Mon 30, 2020 2:15 pm 
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Joined: Feb Fri 27, 2015 3:19 pm
Posts: 93
In that case, the manufacturer has taken steps to protect the equipment. My Panasonic tv has no shields inside, as for my Sony speakers, I don't know because I never took the back cover off which anyway is somehow glued to the cabinet. I could position some shielding but then the whole thing would look ugly.


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