CRT magnetic disturbance

[nasachusetts]

Well, I think I am probably going to go with the Polks. Thanks to everyone for their help, and I'll post back when I get it and let you know what I think.

 

[gedalneil]

Earth is a Magnet as well

I just recently purchased a 36" Sony Wega CRT TV and am most pleased with the quality of this TV. I have had it for a few weeks now and just today noticed the color halos around the edges pretty stong. I do have 2 non-shielded floorstanding speakers both a little over 1 foot away from it. I immeditely moved the away from the TV but the halos were still there. I also have a shielded center speaker that sits on top of it so I moved that also, however, when I took it off the halo got stronger along the top of the screen. I turned off the set for a few minutes and then turned it back on and the picture was back to normal again. I put back the all the speakers and the picture was still fine. Does anyone know what happened? If I look at just a white screen I can still see a little hint of where the halos were but it isn't as obvious as it was for that moment. I thought it had to have been the speakers but I didn't have any trouble the whole time since I've had it and as I've said before the picture is fine now. Would you recommend that I buy expensive magnetically shielded floor speakers? Also, has anyone used a degaussing coil before? Do they work or would I risk permanently damaging the screen? I love this TV and I am not planning on moving to LCD or plasma anytime soon. Trinitron CRT's have a superior picture over any new format in my opinion the 16x9 enhanced option on this unit is amazing and is comparable to alot of HD sets that I've seen. Sorry for rambling on. Thanks for any help you may offer me in advance.

I had the 40 inch XBR. Yes, the speakers could be a problem but there is also another problem that I am not sure has been mentioned yet. It is actually the earths magnetic pull. The magnet in these TV's is so large that it can actually be effected by the earth itself. My 40 inch had a button to adjust this, and it worked (depending on the season). I know this sounds odd, but it is true. So, if you can, try moving your TV around.

 

[nasachusetts]

You know, I was thinking that but I didn't really think it could happen. Hey, someone once told me that my TV has an operators code where I can go in and adjust settings (anyone know how to do this/where to find it) so maybe it has a button like that in there. Oh and one more thing, I had a subwoofer that I took away also, so that could of been helping too. Is this safe to try http://woil.ws/fixmonitor/?

 

[TLS Guy]

I had the 40 inch XBR. Yes, the speakers could be a problem but there is also another problem that I am not sure has been mentioned yet. It is actually the earths magnetic pull. The magnet in these TV's is so large that it can actually be effected by the earth itself. My 40 inch had a button to adjust this, and it worked (depending on the season). I know this sounds odd, but it is true. So, if you can, try moving your TV around.

I think someone was having you on. The earth's magnetic field is minute compared to the field of a speaker or the fields generated by the electromagnets of the CRT. More likely the heavy coils are not properly fixed and the coils move.

 

[Pyrrho]

I think someone was having you on. The earth's magnetic field is minute compared to the field of a speaker or the fields generated by the electromagnets of the CRT. More likely the heavy coils are not properly fixed and the coils move.

No, he is right. The earth's magnetic field does affect very large CRTs, and they have adjustments for this purpose. You can probably download an owner's manual for a 40" CRT TV and read it for yourself. Or possibly find information with an online search.

The reason it is relevant for very large sets (but not small ones) is as I said in my earlier post above; generally speaking, the larger the CRT, the more sensitive it is to magnetic interference. That is because the electron beams are fired from the rear of the tube to the front to make up the picture, and the electron beams are longer with a larger TV (picture tubes are generally deeper when they are bigger across the front). The electron beams are directed with magnetism, and thus can be diverted with magnetism. Thus, a small change in magnetism at the rear of the set will cause a greater difference in a large set where the electron beam hits the front of the tube, which means that it messes up the picture more. This is because the same angle of deflection will cause a greater distance of error at the front of the set (this is simple geometry, where the same angle change will result in a greater distance of difference when going further from the point of origin of the angle). This means, for example, that, typically, one can put a large magnet much closer to a 13" TV than a 27" TV (I selected those numbers, so you might be able to test the matter for yourself by sticking an unshielded speaker above a couple of different sized TVs).

However, he is probably wrong about the advice, as it should be in the manual if it is relevant to the TV mentioned in the post that started this thread. (At least, I hope he has read the manual for his set, and has paid attention to what it says. If not, he should read that before seeking additional advice.)

 

[TLS Guy]

Pyrrho.

That was a very good post. The problem is that the magnetic field from the field coils are AC and the Earth's DC. So yes, in large tubes there does have to be compensation. It seems the mask which has to be of magnetic material is the most vulnerable. The line aperture mask of the Sony Trinitrons seem especially problematic, and are more easily damaged permanently. There is also apparently great risk of damaging them during degaussing.

WARNING about degaussing late model Sony Trinitron CRTs
The following has been confirmed by others.

(From: David Kuhajda (dkuhajda@locl.net).)

You should NEVER use a big degauss coil on ANY SONY WEGA tube, or ANY SONY 27" or larger CRT made after 1997. Sony deliberately put a small amount of magnetic field into the strapping and aperture grill to compensate and improve the convergence. A BIG degauss will remove this and make the tube look very bad.

A BIG manual degauss coil from about 3 feet away should have a low enough field to be safe. (Note: should) I NEVER use the large degauss coils on the Sony tubes after seeing the Sony video of how CRTs have been damaged. I USE a smaller degauss coil and work it on a Variac at a lowered AC voltage, and bring the voltage up each successive pass to degauss the CRT until it is cleared up.

If the internal degauss is not taking care of the problem, you have other things to look at. Has the yoke or yoke purity rings been moved? Have the TV or monitor been dropped? Are all the connections good on the degauss thermister? If it is a three leg thermister it still may be bad as those leave a small current flowing on the older Sony coils. Have any of the extra purity magnets fallen off the yoke or CRT?

Note that Sony tubes do NOT have shadow masks, but they have aperture grills which are an array of incredibly fine wires under tension. A BIG degauss coil can also rip the aperture grill away from the stabilization wires.

This is from the second of two useful articles I found on this topic.

http://www.anatekcorp.com/smask.htm

http://www.repairfaq.org/sam/crtfaq.htm#crtspk

It would seem to me that any center speaker used with one of these Trinitron tubes have not only good shielding, but a second magnet to neutralize the flux emanating from the pole gap. That is going to be few drivers, as it tends to add to driver distortion unless done carefully.

I guess the bottom line is to consider carefully if a Sony Trinitron is a wise choice for home theater.

This is a fascinating problem whose tentacles go a lot deeper than I would have imagined. Seems like a good reason to phase out the CRT.

 

[nasachusetts]

Thanks for that post. I thought it would of been safe manually degaussing my TV. So I will not even bother with it. I received my Polk center speaker today and it is definitely a huge improvement over the KLH sound wise, just not magnetically shielding wise. I still get interference with it sitting right on top of my set. Right now I have it sitting on top of a wooden box on top of my TV about 6" away which helps. I am going to order one of these http://www.amazon.com/exec/obidos/tg/detail/-/B00009WE0X/ref=ord_cart_shr?_encoding=UTF8&m=ATVPDKIKX0DER&v=glance and stack up something on top to rest the speaker on so it is more sturdy. I would also like to get 2 wall mounts for the front speakers when I get them, I need them to be able to hold 20lbs but I can't find any that will hold that much weight. Any ideas of what I can stack on top of the center speaker shelf that wouldn't end up looking too tacky? By lifting it up away from the TV, it needs to be 12" away from the screen so there is no interference. I can post some pics if that would help.
Thanks.

 

[arvind_h]

Sony 32 inch XBR (CRT)

Hi

I placed the center speaker of on my TV plus for a few years plus managed to somehow bump my TV when i moved it from one room to another. While there is picture clarity, i have color patches on the top two conrners of the TV (I am guessing that this is from the Paradigm center speakers more than the bump it recieved). I was also told that I could get this eliminated via degaussing (since the on/off automatic degausser did not work). Also i read on this forum something about BIG degaussers doing damage rather than fixing the problem. I was planning on buying something cheap such as the one shown in the link below.

Any of you experts have any advice on this. Hate to throw the TV out!!!


www_dot_sourcingmap_dot_com/hand-held-crt-picture-tube-degaussing-coil-repair-screen-degausser-p-1454.html[/url]

 

[TLS Guy]

Hi

I placed the center speaker of on my TV plus for a few years plus managed to somehow bump my TV when i moved it from one room to another. While there is picture clarity, i have color patches on the top two conrners of the TV (I am guessing that this is from the Paradigm center speakers more than the bump it recieved). I was also told that I could get this eliminated via degaussing (since the on/off automatic degausser did not work). Also i read on this forum something about BIG degaussers doing damage rather than fixing the problem. I was planning on buying something cheap such as the one shown in the link below.

Any of you experts have any advice on this. Hate to throw the TV out!!!


www_dot_sourcingmap_dot_com/hand-held-crt-picture-tube-degaussing-coil-repair-screen-degausser-p-1454.html[/url]

Did you have the color patches before you bumped it? If not, then you probably have misaligned the yoke by bumping it, and it will have to be realigned. If your TV is a Trinitron, then you will have to be careful with degaussers

 

[croseiv]

LOL! The title of this thread rally caught my eye. Sounds like an interesting doumentary worth watching.

 

[arvind_h]

Did you have the color patches before you bumped it? If not, then you probably have misaligned the yoke by bumping it, and it will have to be realigned. If your TV is a Trinitron, then you will have to be careful with degaussers

I dont believe that I saw the color patches. There was some slight bending. Is it possible to "realign the yoke" by myself? Moving this beast around is a big turn off. Is it worth giving the degaussing a try at all first?

Thanks

 

[jaydog67]

I'll 40th the comment to move your speakers away from your set. Or buy some shielded speakers.


Do you have permanent speakers on your set along the sides?.... If you do it may be possible that the mfgr... may have installed the side speakers wrong causing the color bands.

 

[arvind_h]

Well it was ok for 6 years till I moved the TV and bumped it when i did that so i am certain that it was not that. The question I had if i could align the yoke on my own? If so is there a manual or guidlines? DO i need special instrumentation for it. Thanks very much for your heklp

 

[arvind_h]

Did you have the color patches before you bumped it? If not, then you probably have misaligned the yoke by bumping it, and it will have to be realigned. If your TV is a Trinitron, then you will have to be careful with degaussers

ANy guidance on how to relaign the Yoker? A manual or somethign like that?

Thanks very mch

 

[TLS Guy]

ANy guidance on how to relaign the Yoker? A manual or somethign like that?

Thanks very mch

Do not do this yourself. You need instruments and the voltages are very high. You will kill yourself if you don't know what you are doing.

 

[croseiv]

I see the title to this thread and keep thinking that a solar flare is getting ready to hit or something...