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I have continued on my quest quietly now for what 4 years trying to figure out a "quick" and "easy" method of shielding a coil with conductive paint. Until tonight I hade made very little progress.
The factory coils I have disected seem to have settled on creating a small, inner shell which they pot the windings in. Then they apply the shielding paint, stuff that into the outer shell, and pot it again. That's time consuming and too many steps if you ask me.
Some people paint the shielding onto the inside of the shell, also time consuming and uses a lot of shielding paint which is about $160 a quart. Plus you run the risk of moisture finding its way to the shielding paint and falsing so you have to take care to seal all the edges of the shell with MEK/ABS goo. The shielding paint doesn't like ABS or Polystyrene and epoxy doesn't bond well to the shielding paint which is powder like on the surface.
So there you have two common methods neither of which I favor.
Now what if you could encase your windings in a thick plastic jacket in under 2 seconds?
What if this now insulated winding was dry and ready for shielding paint in under 2 minutes?
What if it was dirt cheap to do so?
Well I'm not ready to declare victory just yet, I really want to see what my test coil looks like on the scope after I apply the shielding using this method but check out these pics.
Here you see part of my RX winding with the coating and shielding paint. Note this leaves a pretty smooth surface on which to apply the paint.
Here I have scraped off the jacket and shielding paint. Thats masking tape showing through underneath. Note the thickness of the jacket.
Here is a closeup of a zip tie, as you can see it has a nice thick coating.
I don't know if the jacket is thick enough to put the proper spacing between the winding and the shielding paint but I only applied a single coat of what I'm calling liquid spiral wrap. I can easily apply a second and third coat to build up more thickness if required.
So what is this wonder substance? Its a translucent thermo plastic rubber that is oil free and odor free. It comes in 1 lb bricks and you melt them to a liquid state. Dip the winding in for about 1 second and remove, presto its instantly coated. The heating pots they sell are very expensive but I picked up a large electric 2 inch deep pan at Walmart for about $20 to melt mine. The pics above are of a single dip, I did tip part of this winding a second time and it came out twice again as thick. Best of all the shielding paint loves it and I was able to flex the winding without it flaking off.
I don't remember the cost, it was pretty cheap as I recall. The free sample they sent me was 5 pounds if that gives you an idea. Here's a link to the site. http://www.dipseal.com/page3.html you want the DS99K.
Note, you can reheat this stuff pretty much indefinately. I think the upper limit was like 500 times but they said if you are adding new ingots on a regular basis it pretty much never goes bad.
Charles
The factory coils I have disected seem to have settled on creating a small, inner shell which they pot the windings in. Then they apply the shielding paint, stuff that into the outer shell, and pot it again. That's time consuming and too many steps if you ask me.
Some people paint the shielding onto the inside of the shell, also time consuming and uses a lot of shielding paint which is about $160 a quart. Plus you run the risk of moisture finding its way to the shielding paint and falsing so you have to take care to seal all the edges of the shell with MEK/ABS goo. The shielding paint doesn't like ABS or Polystyrene and epoxy doesn't bond well to the shielding paint which is powder like on the surface.
So there you have two common methods neither of which I favor.
Now what if you could encase your windings in a thick plastic jacket in under 2 seconds?
What if this now insulated winding was dry and ready for shielding paint in under 2 minutes?
What if it was dirt cheap to do so?
Well I'm not ready to declare victory just yet, I really want to see what my test coil looks like on the scope after I apply the shielding using this method but check out these pics.
Here you see part of my RX winding with the coating and shielding paint. Note this leaves a pretty smooth surface on which to apply the paint.
Here I have scraped off the jacket and shielding paint. Thats masking tape showing through underneath. Note the thickness of the jacket.
Here is a closeup of a zip tie, as you can see it has a nice thick coating.
I don't know if the jacket is thick enough to put the proper spacing between the winding and the shielding paint but I only applied a single coat of what I'm calling liquid spiral wrap. I can easily apply a second and third coat to build up more thickness if required.
So what is this wonder substance? Its a translucent thermo plastic rubber that is oil free and odor free. It comes in 1 lb bricks and you melt them to a liquid state. Dip the winding in for about 1 second and remove, presto its instantly coated. The heating pots they sell are very expensive but I picked up a large electric 2 inch deep pan at Walmart for about $20 to melt mine. The pics above are of a single dip, I did tip part of this winding a second time and it came out twice again as thick. Best of all the shielding paint loves it and I was able to flex the winding without it flaking off.
I don't remember the cost, it was pretty cheap as I recall. The free sample they sent me was 5 pounds if that gives you an idea. Here's a link to the site. http://www.dipseal.com/page3.html you want the DS99K.
Note, you can reheat this stuff pretty much indefinately. I think the upper limit was like 500 times but they said if you are adding new ingots on a regular basis it pretty much never goes bad.
Charles
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