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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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electron gun(s) and magnetic fields
I have a 54" RCA rear projection. I had a new hardwood floor installed
with an electric heating grid underneath. The grid consists of heavy screen mesh, similar to window screen but 2-3 times heavier wire, laid in one continuous circuit back and forth across the room. There is a high voltage, low amperage current running through it. Here's the problem - when the heater is on, the guns in my tv misalign, looks like 3-d image viewed without the correct glasses. Soon as I turn off the heat, the tv returns to normal. How can I shield the tv from the floor induced field? Faraday cage? (I don't really want to view thru wire mesh!) Grounded sheet of steel under the set? Raise the set a foot or two off the floor? Both? Any suggestions, particularly from those who have solved this problem or engineers, would be greatly appreciated! Real E-mail: gpdewitt at earth link dot net (no space in earthlink) |
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"Gary DeWitt" wrote in message om... | I have a 54" RCA rear projection. I had a new hardwood floor installed | with an electric heating grid underneath. The grid consists of heavy | screen mesh, similar to window screen but 2-3 times heavier wire, laid | in one continuous circuit back and forth across the room. There is a | high voltage, low amperage current running through it. Here's the | problem - when the heater is on, the guns in my tv misalign, looks | like 3-d image viewed without the correct glasses. Soon as I turn off | the heat, the tv returns to normal. How can I shield the tv from the | floor induced field? Faraday cage? (I don't really want to view thru | wire mesh!) Grounded sheet of steel under the set? Raise the set a | foot or two off the floor? Both? Any suggestions, particularly from | those who have solved this problem or engineers, would be greatly | appreciated! Interesting! 1. The higher off the floor the TV is, the lesser the effect. 2. Alternate layers of sheet steel and aluminium under the TV, insulated from each other by paper, might diminish the effect. 3. Use a separate heater when you want to watch TV. N |
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"Gary DeWitt" wrote in message
om... I have a 54" RCA rear projection. I had a new hardwood floor installed with an electric heating grid underneath. The grid consists of heavy screen mesh, similar to window screen but 2-3 times heavier wire, laid in one continuous circuit back and forth across the room. There is a high voltage, low amperage current running through it. Here's the problem - when the heater is on, the guns in my tv misalign, looks like 3-d image viewed without the correct glasses. Soon as I turn off the heat, the tv returns to normal. How can I shield the tv from the floor induced field? Faraday cage? (I don't really want to view thru wire mesh!) Grounded sheet of steel under the set? Raise the set a foot or two off the floor? Both? Any suggestions, particularly from those who have solved this problem or engineers, would be greatly appreciated! Real E-mail: gpdewitt at earth link dot net (no space in earthlink) 2 ideas Find someone who has a heap of mu-metal sheets and lay under TV or trace with sniffer or pipe/metal detector the exact run of heater wires at a point away from TV. Excavate down and cut and bypass the few loops that go under the TV electronic hints and repair briefs , schematics/manuals list on http://homepages.tcp.co.uk/~diverse |
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Any iron or steel (but not stainless steel) shield (such as sheet metal)
that you can place between the heater and the TV will help. Iron has much lower reluctance than air, so the magnetic field from the heater will be concentrated in the shield. Stainless steel is weird in this regard and usually won't help even though it can be made up of mostly iron. |
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Jamie writes:
sorry, i don't think you can. you would have to align the TV with the heat on and then align it again after. That won't help if the heating grid is powered from AC. --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header is ignored. To contact me, please use the feedback form on the S.E.R FAQ Web sites. |
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Also the Manufacturer will be absolutely no assistance regarding this since
the symptom is being induced by it's environment. As noted, you may want to consider a DLP, MMD, or Plasma television reciever. Or, move the curent television to a room that is not heated in such a manner to resolve that particular problem. "Sam Goldwasser" wrote in message ... Jamie writes: sorry, i don't think you can. you would have to align the TV with the heat on and then align it again after. That won't help if the heating grid is powered from AC. --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header is ignored. To contact me, please use the feedback form on the S.E.R FAQ Web sites. |
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sorry, i don't think you can.
you would have to align the TV with the heat on and then align it again after. the only thing i can think of is that the electric heaters are not properly laid out over laying each other to cancel each other out which in this case can be hard to do.. you could try elivating the tv on a stand or get your self a DLP projection. Gary DeWitt wrote: I have a 54" RCA rear projection. I had a new hardwood floor installed with an electric heating grid underneath. The grid consists of heavy screen mesh, similar to window screen but 2-3 times heavier wire, laid in one continuous circuit back and forth across the room. There is a high voltage, low amperage current running through it. Here's the problem - when the heater is on, the guns in my tv misalign, looks like 3-d image viewed without the correct glasses. Soon as I turn off the heat, the tv returns to normal. How can I shield the tv from the floor induced field? Faraday cage? (I don't really want to view thru wire mesh!) Grounded sheet of steel under the set? Raise the set a foot or two off the floor? Both? Any suggestions, particularly from those who have solved this problem or engineers, would be greatly appreciated! Real E-mail: gpdewitt at earth link dot net (no space in earthlink) |
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I have a 54" RCA rear projection. I had a new hardwood floor installed with an electric heating grid underneath. The grid consists of heavy screen mesh, similar to window screen but 2-3 times heavier wire, laid in one continuous circuit back and forth across the room. There is a high voltage, low amperage current running through it. Here's the problem - when the heater is on, the guns in my tv misalign, looks like 3-d image viewed without the correct glasses. Soon as I turn off the heat, the tv returns to normal. How can I shield the tv from the floor induced field? Faraday cage? (I don't really want to view thru wire mesh!) Grounded sheet of steel under the set? Raise the set a foot or two off the floor? Both? Any suggestions, particularly from those who have solved this problem or engineers, would be greatly appreciated! Swap your rear-projection TV for a Plasma or LCD. Or use an alternative heat source. I am not trying to be flippant, if the convergence shift is as bad as you say, I don't think you will ever shield it. -- Graham. %profound_observation% |
#10
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Here's an idea that'll blow you f______ mind
An RCA doesn't need gravity to cool the CRTs, so, turn it upside down. Unfortunately you'll have to make a top for it and have it completely re-setup for this mode, but this will put the CRTs at the top, well away from the EMI. To get the desired screen height you might not really be able to put anything on top of it, the speakers will be at the top (and reversed, but you know what to do), and I would suggest a carefully designed cooling system. Yes a fan, but with it setup to draw air the right way through the chassis. In this case, this is the best I can do. If you're in NE Ohio I can do it for you, probably pretty reasonable. I'm not really that cheap, but it'll be well less than getting a DLP, and don't get a plasma until they perfect them. Just build whatever stand it takes to get the screen as high as you want it, and BTW, all the stuff that used to be on top could now be on shelves underneath. While this might be a fine example of lateral thinking, it may or may not be right for you, but it is an idea. JURB |
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2 ideas
Find someone who has a heap of mu-metal sheets and lay under TV What is mu-metal, and is there a source where it can be salvaged from? I saw something like this on the web, poorly described and priced at hundreds per square foot! |
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(Gary DeWitt) writes:
2 ideas Find someone who has a heap of mu-metal sheets and lay under TV What is mu-metal, and is there a source where it can be salvaged from? I saw something like this on the web, poorly described and priced at hundreds per square foot! Mumetal is a highly magnetically permiable material. However, it's expensive as you note, and difficult to work (you can't bend it without reannealing for maximum effectiveness). And, since you can't see through it, at least the front of your TV will be exposed. If it is simply put under the TV but the magnetic field will still come in from the beyond. You will end up spending much more on bandaids than on an LCD TV. --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header is ignored. To contact me, please use the feedback form on the S.E.R FAQ Web sites. |
#14
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"Charles Schuler" wrote in message ... Any iron or steel (but not stainless steel) shield (such as sheet metal) that you can place between the heater and the TV will help. Iron has much lower reluctance than air, so the magnetic field from the heater will be concentrated in the shield. Stainless steel is weird in this regard and usually won't help even though it can be made up of mostly iron. Additional information: "So, in our example of placing a steel plate between the magnet and the area we desire to shield from the magnetic field, the ends of the steel plate will have all the flux lines possible trying to get into it, traveling down to where they must exit to get back to the magnet (the flux channel) and exiting in a big bunch. Remembering that the more flux lines, the stronger the field, what we have accomplished with our actions is to make the magnetic field near the ends of the steel plate stronger (collected flux lines) and more inhomogeneous (bent more). Both of these points make the stray magnetic field more of a problem near the ends of the steel plate. One way to overcome this problem is to make the steel plate much larger that the desired area to shield. As the dimensions of the steel plate get larger, the larger the area of the lowest magnetic field behind the steel plate." It would seem that if the steel plate was large enough, the flux lines at its edges should be far enough away from the electron guns and the problem will be solved or at least greatly reduced. Source: http://www.acornnmr.com/appnotes/shielding.htm |
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"Sam Goldwasser" wrote in message ... | Mumetal is a highly magnetically permiable material. However, it's expensive | as you note, and difficult to work (you can't bend it without reannealing for | maximum effectiveness). And a cheaper alternative is alternate layers of steel and aluminium, insulated with paper. NM |
#16
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"JURB6006" wrote in message ... Here's an idea that'll blow you f______ mind An RCA doesn't need gravity to cool the CRTs, so, turn it upside down. Unfortunately you'll have to make a top for it and have it completely re-setup for this mode, but this will put the CRTs at the top, well away from the EMI. To get the desired screen height you might not really be able to put anything on top of it, the speakers will be at the top (and reversed, but you know what to do), and I would suggest a carefully designed cooling system. Yes a fan, but with it setup to draw air the right way through the chassis. In this case, this is the best I can do. If you're in NE Ohio I can do it for you, probably pretty reasonable. I'm not really that cheap, but it'll be well less than getting a DLP, and don't get a plasma until they perfect them. Just build whatever stand it takes to get the screen as high as you want it, and BTW, all the stuff that used to be on top could now be on shelves underneath. While this might be a fine example of lateral thinking, it may or may not be right for you, but it is an idea. JURB I would be concerned about coolant leaking and airflow for cooling, not to mention this would look pretty ugly. I think it'd be easier to set the TV up on something, a shelf a foot off the floor would probably be plenty, it's worth a try, cinder blocks and a piece of plywood will do the trick, something nicer looking can always be built once the problem is fixed. |
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On Fri, 12 Nov 2004 13:30:27 -0800 Jamie
wrote: the only thing i can think of is that the electric heaters are not properly laid out over laying each other to cancel each other out which in this case can be hard to do.. I agree with this. I don't know if the makers of this kind of heater have thought of this problem, but they should have. It should be possible to lay the heating material in such a way that the external field is minimized, but it sounds like this was not done in your case. It might be worthwhile to check with the maker of your heater to see if they have guidelines in installing it. I have no idea how hard it might be to get it corrected. I agree with Sam, that trying to shield it is likely to be futile. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
#18
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On 12 Nov 2004 22:30:12 GMT (JURB6006) wrote:
An RCA doesn't need gravity to cool the CRTs, so, turn it upside down. Very interesting, and creative, suggestion. It's a lot of work, but probably a lot less than digging up the floor. It's also possible that it would not help significantly. It all depends on the nature of the mag field set up by the heating coils. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
#19
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the only thing i can think of is that the electric heaters are not properly laid out over laying each other to cancel each other out which in this case can be hard to do.. you could try elivating the tv on a stand or get your self a DLP projection. I see, you mean like a bifilar coil? Is that standard practise with underfloor heating? We don't see much of it now here in the UK. Was put in to apartments in the '60's but became notoriously expensive to run. -- Graham. %Profound_observation% |
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