TVs and unshielded speakers

[Jo]

What kind of damage can be done to CRT TVs from unshielded speakers?
Do boomboxes from around 2002 usually have shielded or unshielded
speakers?

 

[whit3rd]

On May 21, 10:59 pm, Jo <AGirlName...@gmail.com> wrote:

What kind of damage can be done to CRT TVs from unshielded speakers?
Do boomboxes from around 2002 usually have shielded or unshielded
speakers?

Television CRTs have internal elements (shadow mask and electrodes)
that can be misaligned, bent, or damaged by a strong magnet.

Speakers usually have strong magnets, BUT those are for the voice coil
and
the field doesn't extend beyond an inch or two. A few compact
speakers may
have enough field outside the box to distort a color picture (but that
doesn't mean that there's any permanent damage),
but only if you disassemble the speaker will you get any magnetic
parts capable of
doing real, permanent damage. All speaker magnet designs are
shielded
by design, because it's expensive to waste the field on empty space...

I've tested magnetic linear motors (big 'uns, over 20 pounds of magnet
material)
and the field is harmless at a few inches. For a boombox speaker,
maybe
two inches magnet-to-screen is too close. Four inches should be OK.

 

[William Sommerwerck]

What kind of damage can be done to CRT TVs from unshielded
speakers?

Little or none.

Several years ago, as an experiment, I shut off a powerful bulk tape eraser
right to a 36" Trinitron to see what happened. It produced what was
apparently a permanent color splotch that would not go away, no matter what
I did.

When the set was moved to my bedroom in March, the splotch magically
vanished. I was told that my original "abuse" has caused the aperture grill
wires to "tangle", and that moving (and therefore vibrating) the set had
made them come loose. In fact, Sony had a guy on the production line who
whacked CRTs with a rubber mallet to prevent or reverse this.

A TV set's automatic degaussing coil can remove all but the worst
magnetization from the shadow mask. It simply isn't something to worry
about.

Another poster said "All speaker magnet designs are shielded by design,
because it's expensive to waste the field on empty space." This is
misleading. Simply blocking the external magnetic field does not make it
available to strengthen the field around the voice coil. Rather, many, if
not most, speaker magnets are "shielded" by using two magnets, arranged so
that their fields add at the voice coil, but largely cancel outside.

 

[William Sommerwerck]

Last night I realized there was a green spot at the top of my TV
screen. That's when I realized some jerk had put their boombox right
on top the TV earlier in the day. There's two inches between the spot
and the top of the TV. So the speaker in the boombox was probably
three to four inches away from the spot. It seems like that boombox is
what caused the green spot. It would be too much of a coincidence for
the spot to appear the same day the boombox had been placed on the TV.

So, will this go away by itself? It sounds like you're saying the
degaussing thing should fix it. I would imagine something like this
would void the warranty and the free repair program thing I purchased.

There's no reason you would need an external degaussing coil. * The next
time you turn it on, its built-in degaussing system should clear the
magnetization. And if you did use an external demagnetizer, the manufacturer
would have no way of knowing.

* As flat-panel displays displace CRTs, degaussing coils will become the
proverbial hen's teeth.

 

[AZ Nomad]

On Fri, 22 May 2009 13:09:06 -0700, William Sommerwerck <grizzledgeezer@comcast.net> wrote:

Last night I realized there was a green spot at the top of my TV
screen. That's when I realized some jerk had put their boombox right
on top the TV earlier in the day. There's two inches between the spot
and the top of the TV. So the speaker in the boombox was probably
three to four inches away from the spot. It seems like that boombox is
what caused the green spot. It would be too much of a coincidence for
the spot to appear the same day the boombox had been placed on the TV.

So, will this go away by itself? It sounds like you're saying the
degaussing thing should fix it. I would imagine something like this
would void the warranty and the free repair program thing I purchased.

There's no reason you would need an external degaussing coil. * The next
time you turn it on, its built-in degaussing system should clear the
magnetization. And if you did use an external demagnetizer, the manufacturer
would have no way of knowing.

They are only strong enough to counter the earth's magnetic field. If
you put a magnet close enough to magnetize the CRT, the degauser will
probably never be able to undo it.

Use a bulk tape eraser.

 

[William Sommerwerck]

They are only strong enough to counter the earth's magnetic field.
If you put a magnet close enough to magnetize the CRT, the
degauser will probably never be able to undo it.

Have you ever tried it? Or are you just theorizing?

Why don't you actually do it, then report back what you find?

 

[AZ Nomad]

On Fri, 22 May 2009 13:58:53 -0700, William Sommerwerck <grizzledgeezer@comcast.net> wrote:

They are only strong enough to counter the earth's magnetic field.
If you put a magnet close enough to magnetize the CRT, the
degauser will probably never be able to undo it.

Have you ever tried it? Or are you just theorizing?

Why don't you actually do it, then report back what you find?

I have on several TV's and monitors. I used to play with magnets and
have never seen any degauser remove the slightest spot. Bulk tape
erasers work although you have to back off slowly before killing the
power or they'll leave new spots.

Why the don't you try it yourself before making more of an ass of
yourself?

 

[Jo]

On 22 May, 06:05, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

What kind of damage can be done to CRT TVs from unshielded
speakers?

Little or none.

Several years ago, as an experiment, I shut off a powerful bulk tape eraser
right to a 36" Trinitron to see what happened. It produced what was
apparently a permanent color splotch that would not go away, no matter what
I did.

When the set was moved to my bedroom in March, the splotch magically
vanished. I was told that my original "abuse" has caused the aperture grill
wires to "tangle", and that moving (and therefore vibrating) the set had
made them come loose. In fact, Sony had a guy on the production line who
whacked CRTs with a rubber mallet to prevent or reverse this.

A TV set's automatic degaussing coil can remove all but the worst
magnetization from the shadow mask. It simply isn't something to worry
about.

Another poster said "All speaker magnet designs are shielded by design,
because it's expensive to waste the field on empty space." This is
misleading. Simply blocking the external magnetic field does not make it
available to strengthen the field around the voice coil. Rather, many, if
not most, speaker magnets are "shielded" by using two magnets, arranged so
that their fields add at the voice coil, but largely cancel outside.

Last night I realized there was a green spot at the top of my TV
screen. That's when I realized some jerk had put their boombox right
on top the TV earlier in the day. There's two inches between the spot
and the top of the TV. So the speaker in the boombox was probably
three to four inches away from the spot. It seems like that boombox is
what caused the green spot. It would be too much of a coincidence for
the spot to appear the same day the boombox had been placed on the TV.

So, will this go away by itself? It sounds like you're saying the
degaussing thing should fix it. I would imagine something like this
would void the warranty and the free repair program thing I purchased.

 

[William Sommerwerck]

"AZ Nomad" <aznomad.3@PremoveOBthisOX.COM> wrote in message
news:slrnh1e6qv.804.aznomad.3@ip70-176-155-130.ph.ph.cox.net...

On Fri, 22 May 2009 13:58:53 -0700, William Sommerwerck
grizzledgeezer@comcast.net> wrote:

They are only strong enough to counter the earth's magnetic field.
If you put a magnet close enough to magnetize the CRT, the
degauser will probably never be able to undo it.

Have you ever tried it? Or are you just theorizing?
Why don't you actually do it, then report back what you find?

I have on several TV's and monitors. I used to play with magnets and
have never seen any degauser remove the slightest spot. Bulk tape
erasers work although you have to back off slowly before killing the
power or they'll leave new spots.

Why the don't you try it yourself before making more of an ass of
yourself?

I've done it. And it works.

 

[Sjouke Burry]

Jo wrote:

What kind of damage can be done to CRT TVs from unshielded speakers?
Do boomboxes from around 2002 usually have shielded or unshielded
speakers?
A boom box is sitting right under my crt tv as we speak.

Has been there for the last 10 years.
No problem.

 

[Jim Yanik]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:gv70pd$aia$1@news.eternal-september.org:

Last night I realized there was a green spot at the top of my TV
screen. That's when I realized some jerk had put their boombox right
on top the TV earlier in the day. There's two inches between the spot
and the top of the TV. So the speaker in the boombox was probably
three to four inches away from the spot. It seems like that boombox
is what caused the green spot. It would be too much of a coincidence
for the spot to appear the same day the boombox had been placed on
the TV.

So, will this go away by itself? It sounds like you're saying the
degaussing thing should fix it. I would imagine something like this
would void the warranty and the free repair program thing I
purchased.

There's no reason you would need an external degaussing coil. * The
next time you turn it on, its built-in degaussing system should clear
the magnetization. And if you did use an external demagnetizer, the
manufacturer would have no way of knowing.

* As flat-panel displays displace CRTs, degaussing coils will become
the proverbial hen's teeth.

I used to work on TEK 650 series video monitors(TEK service centers),and we
used an external degaussing coil,called for in the calibration procedure.
The internal 'DG' coils are not as strong as the external ones,and you have
to move them around the face of the tube,you cant do that with the internal
coil.

TV repair shops all used them,made good money degaussing TVs people had
screwed up with magnets.
It should not affect your warranty.

--
Jim Yanik
jyanik
at
kua.net

 

[Jim Yanik]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in
news:gv772q$rvd$1@news.eternal-september.org:

"AZ Nomad" <aznomad.3@PremoveOBthisOX.COM> wrote in message
news:slrnh1e6qv.804.aznomad.3@ip70-176-155-130.ph.ph.cox.net...
On Fri, 22 May 2009 13:58:53 -0700, William Sommerwerck
grizzledgeezer@comcast.net> wrote:

They are only strong enough to counter the earth's magnetic field.
If you put a magnet close enough to magnetize the CRT, the
degauser will probably never be able to undo it.

Have you ever tried it? Or are you just theorizing?
Why don't you actually do it, then report back what you find?

I have on several TV's and monitors. I used to play with magnets and
have never seen any degauser remove the slightest spot. Bulk tape
erasers work although you have to back off slowly before killing the
power or they'll leave new spots.

that's the way you do it with an external TV degaussing coil.You work the
coil around the CRT face several times,gradually back away until you're a
few feet away and -then- click off the coil.

Why the don't you try it yourself before making more of an ass of
yourself?

I've done it. And it works.

--
Jim Yanik
jyanik
at
kua.net

 

[JB]

If you put a magnet close enough to magnetize the CRT, the
degauser will probably never be able to undo it.

Have you ever tried it? Or are you just theorizing?
Why don't you actually do it, then report back what you find?

I have on several TV's and monitors. I used to play with magnets and
have never seen any degauser remove the slightest spot. Bulk tape
erasers work although you have to back off slowly before killing the
power or they'll leave new spots.

that's the way you do it with an external TV degaussing coil.You work the
coil around the CRT face several times,gradually back away until you're a
few feet away and -then- click off the coil.


Why the don't you try it yourself before making more of an ass of
yourself?

I've done it. And it works.

And now that the trade secret is out... A blowdrier might be a fair
substitute, or even a wall-wort on a long extension cord. Another
possibility is purity magnets getting thrown off by being remangnitized.
Might need a degauss of the entire chassis followed up by purity and
convergence alignment. Speakers and TVs don't mix.

 

[Smitty Two]

In article <4a172006$0$6673$703f8584@textnews.kpn.nl>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

Jo wrote:
What kind of damage can be done to CRT TVs from unshielded speakers?
Do boomboxes from around 2002 usually have shielded or unshielded
speakers?
A boom box is sitting right under my crt tv as we speak.
Has been there for the last 10 years.
No problem.

Would you humor me with an experiment? Move the boombox away, and see
whether the picture changes, then put it back.

I once put a 30" length of railroad rail on top of my TV. You know, a
bachelor's idea of home decorating. It sat there for a few years, and
never caused any problem with the picture.

When I finally moved it, the color blotches were horrible. But the
external degaussing coil cleared it right up.

 

[Sjouke Burry]

Smitty Two wrote:

In article <4a172006$0$6673$703f8584@textnews.kpn.nl>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

Jo wrote:
What kind of damage can be done to CRT TVs from unshielded speakers?
Do boomboxes from around 2002 usually have shielded or unshielded
speakers?
A boom box is sitting right under my crt tv as we speak.
Has been there for the last 10 years.
No problem.

Would you humor me with an experiment? Move the boombox away, and see
whether the picture changes, then put it back.

I once put a 30" length of railroad rail on top of my TV. You know, a
bachelor's idea of home decorating. It sat there for a few years, and
never caused any problem with the picture.

When I finally moved it, the color blotches were horrible. But the
external degaussing coil cleared it right up.
Done that a number of times, moving furniture around.

I have never seen localized color errors, except when I was
fooling around with some magnets, mainly from old diskdrives.
The de-gausing build into my tv took care of the results
of those experiments

 

[William Sommerwerck]

What kind of damage can be done to CRT TVs from unshielded
speakers? Do boomboxes from around 2002 usually have shielded
or unshielded speakers?

A boom box is sitting right under my CRT TV as we speak.
Has been there for the last 10 years. No problem.

Would you humor me with an experiment? Move the boombox away,
and see whether the picture changes, then put it back.

I once put a 30" length of railroad rail on top of my TV. You know, a
bachelor's idea of home decorating. It sat there for a few years, and
never caused any problem with the picture.
When I finally moved it, the color blotches were horrible. But the
external degaussing coil cleared it right up.

In fairness, I was claiming that the internal degaussing coil would be
sufficient. (It's generally more powerful than would be needed simply to
clear the magnetization induced by moving the set through the Earth's
magnetic field.) I stand by that, but it's certainly true that the shadow
mask could be so badly magnetized that a more-powerful external coil would
be needed.

My 36" Sony WEGA sat between two Apogee Diva speakers. There was no visible
impurity from the speakers. On one occasion, when I had to move the
right-front speaker to re-glue the midrange ribbon, all sorts of colorations
appeared on the screen. They pretty much disappeared when the speaker was
returned to its usual position. If you bring a big magnet near the CRT, then
move it away in the same direction it arrived, much of the induced
magnetization will be removed.

To put it another way -- you have to go out of your way to badly magnetize a
shadow mask. If you remember the example I gave, despite having shut off a
very powerful bulk eraser right next to the CRT, I hadn't permanently
magnetized the aperture grille -- simply knocked it out of alignment.

Do any of you remember Zenith's spinning wand? It was a small bar magnet
that could be spun by hand. The idea was to allow demagnetizing small areas
without having to plug in a coil.

 

[Michael A. Terrell]

AZ Nomad wrote:

On Fri, 22 May 2009 13:58:53 -0700, William Sommerwerck <grizzledgeezer@comcast.net> wrote:
They are only strong enough to counter the earth's magnetic field.
If you put a magnet close enough to magnetize the CRT, the
degauser will probably never be able to undo it.

Have you ever tried it? Or are you just theorizing?

Why don't you actually do it, then report back what you find?

I have on several TV's and monitors. I used to play with magnets and
have never seen any degauser remove the slightest spot. Bulk tape
erasers work although you have to back off slowly before killing the
power or they'll leave new spots.

Why the don't you try it yourself before making more of an ass of
yourself?

Too strong of a magnetic field from that bulk tape eraser can warp
the shadow mask It can even pull it loose inside the bell. I've seen
the damage on some CRTs, but its yours to destroy. I've degaussed
thousands of CRTs in the last 40+ years.


--
You can't have a sense of humor, if you have no sense!

 

[Ron]

Smitty Two wrote:

In article <4a172006$0$6673$703f8584@textnews.kpn.nl>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

Jo wrote:
What kind of damage can be done to CRT TVs from unshielded speakers?
Do boomboxes from around 2002 usually have shielded or unshielded
speakers?
A boom box is sitting right under my crt tv as we speak.
Has been there for the last 10 years.
No problem.

Would you humor me with an experiment? Move the boombox away, and see
whether the picture changes, then put it back.

I once put a 30" length of railroad rail on top of my TV. You know, a
bachelor's idea of home decorating. It sat there for a few years, and
never caused any problem with the picture.

When I finally moved it, the color blotches were horrible. But the
external degaussing coil cleared it right up.

Did it have a loco or two on the track? with permanent magnets in the
motors?

Ron

 

[Ian Jackson]

In message <4a172006$0$6673$703f8584@textnews.kpn.nl>, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnll> writes

Jo wrote:
What kind of damage can be done to CRT TVs from unshielded speakers?
Do boomboxes from around 2002 usually have shielded or unshielded
speakers?
A boom box is sitting right under my crt tv as we speak.
Has been there for the last 10 years.
No problem.

Some of the worst offenders are the small speakers used for car
hands-free telephone installations. They are powerful little fellows,
and can affect CRT pictures from a distance of more than 18". They are
not exactly hi-fi, but are sometimes used as external speakers for CB
and amateur radio equipment, and must be kept well away from any TV set
in the vicinity.
--
Ian

 

[David Nebenzahl]

On 5/23/2009 2:49 AM Ron spake thus:

Smitty Two wrote:

In article <4a172006$0$6673$703f8584@textnews.kpn.nl>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

Jo wrote:

What kind of damage can be done to CRT TVs from unshielded
speakers? Do boomboxes from around 2002 usually have shielded
or unshielded speakers?

A boom box is sitting right under my crt tv as we speak.
Has been there for the last 10 years.
No problem.

Would you humor me with an experiment? Move the boombox away, and see
whether the picture changes, then put it back.

I once put a 30" length of railroad rail on top of my TV. You know, a
bachelor's idea of home decorating. It sat there for a few years, and
never caused any problem with the picture.

When I finally moved it, the color blotches were horrible. But the
external degaussing coil cleared it right up.

Did it have a loco or two on the track? with permanent magnets in the
motors?

Real loco motors (i.e., traction motors) don't have magnets. Use field
coils.


--
Found--the gene that causes belief in genetic determinism