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Discussion Starter · #1 ·
Hi.


I tryed to set up my BD 801 on the floor in my basement HT room, but as soon as the heatingcables kicked in, the image started to shake. I had to set it up on a table to get it away from the floor.


Now I have become quite fond of this pj, and would like to ceilingmount it, but then I remembered one thing. The floor upstairs also has electric heating, and thus also my ceiling would probably procuce the same distortion as I found when trying to floormount it.


Does anybody know of a way to shield the pj so that the electromagnetic field from the cables can't reach the pj?


Frode
 

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Frode - I am sorry that I am not familiar with the power used in Norway, but from the description of your problem, it is obviously AC and at a low enough frequency to be visible. The electromagnetic field strength generated by the current in your heating wires is proportional to 1/r where r is the distance from the plane of the heating wires, so the further away you get, the less field strength you will have. My first thought was to install a rectifier on your heating circuit so it would be DC which would have a constant field stength and you could "tune" out its effect when you set up your projector. Unfortunately, when your thermostat would turn off, you would no longer be adjusted properly. I think the bottom line is that you will need to shield your projector from the unwanted field. The best material I am aware of is mu-metal. While I can't think of a source, I believe it can be purchased in sheets that you could affix to your ceiling before you mount your projector. If I am not mistaken, mu-metal is fairly expensive. Maybe someone else has a better and cheaper idea. Can you live with just turning off the heat upstairs while watching your projector?

Good Luck,

Bob
 

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Would not just a sheet ( maybe a couple feet bigger than the PJ in all directions) of cheap thin steel that has been grounded work? Might be worth trying.


Deron
 

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The sheetmetal might be worth a try as it is ferrous, but I had bad luck many years ago when I tried to perch a direct view TV on top of a home made sub-woofer. I covered the top of the sub cabinet with sheetmetal which was about a foot or so wider than the TV. While it reduced the problem, I ended up moving the sub. Don't know for sure if it would have worked if I covered the sides of the enclosure or not as I didn't go that far with it. I don't think it is necessary to ground the metal however, as I don't think any voltage potential is being built up - just an unwanted electromagnetic field.


Thanks,

Bob
 

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I agree with the sheet idea. It should effectively disperse the field from around the projector. Try a sheet on the floor. Works for speakers.


Marc
 

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Discussion Starter · #6 ·
Thank you for your input so far, I will definetly "google" on mu-metal. In Norway we have AC 220 volts @50 hz, so a lot of appliances can produce a humming sound from the low freq. I guess the best thing to do is to power on the floor, and test different materials there.


I could power off the floor upstairs, but I dont like the constant magnetic interference reaching the pj even when it's turned off. People say that even the earths magnetism makes the convergence shift.


If I decide to just shut off the floor while watching, I would need to be ashured that the magnetic influence will not harm the pj in any way. Finetuning convergence is done in 10 minutes so that is not a big deal for me.


Frode
 
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