• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Designing an Interstage Transformer

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Normal commercial available nomex has not a very low dielectical constance as far a a know. Mostly it's between 3.5 and 4.5. Nomex is available in many different qualities and the harder its pressed the higher the ε is. It can be up till 8! There is a quality unpressed nomex with a ε=1.3 however this is not standard available. If anybody knows a suplier please send me a pm.

http://www.osdasrl.com.ar/pdf/tec410.pdf
 
I used to buy at "Electro aislante" in Buenos Aires, they had a shop at Av. San Juan but then moved to Av Entre Ríos.
Only problem is they are real *Industry* suppliers and demand a commercial CUIT (Argentine IRS Company ID number) to sell to you.
Get a friend to "lend" you their number.
My IRSA wholesale wire supplier also has some Nomex thicknesses available, you can buy "black" (no papers) from him:
ABRAHIM EMILIO ALAMBRE DE COBRE ESMALTADOS
CHILE 639, 1098 BUENOS AIRES | Teléfono : (011) 436 163 66
Not that much problem with papers, if you pay cash, but they heve no In ternet page, you must go there "in person" and see what they have available.
They fear robbery , so you will have to call them, make them trust you, and probably talk a lot through a 2" hole in their bullet proof door before they open it.
And even so, they may not sell you at all.
Tell them "Fahey de La Boca" is your friend and told you to buy there.
And even so they may ring me to check I know you, so send me a mail a few days before, just in case.
 
I know it is better but who sells it and what are the costs?

I know many nomex surpliers sell laminated nomex ( mylar or kapton). These nomex are worse.

very good is also paper ε=2

Sorry, I do not sell NOMEX and my provider is a "Kiosk" seedy, in Córdoba city.

NOMEX 410 is something like laminated, is "calendered"

Paper is good dry, what about varnish or moisture ?
 
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I would think in order to get dielectric constants approaching 1 you need a very porous material (mostly air). In lieu of the expensive materials such as expanded teflon and nomex why not just use a glass cloth electrical tape (thermosetting or apply a thin layer of uralane to the cloth) ?

There used to be at least one chemical stripper for the poyimide wire (worked great) but given its health and environmental concerns I would strongly avoid it (now wish I had as well).

Thanks
-Antonio
 
I would think in order to get dielectric constants approaching 1 you need a very porous material (mostly air). In lieu of the expensive materials such as expanded teflon and nomex why not just use a glass cloth electrical tape (thermosetting or apply a thin layer of uralane to the cloth) ?

Because through the pores, you lose insulation, moist air has a breakdown voltage of about 900 V.

Glass ε > 4 , uralane has a dielectric constant similar to Teflon, so the mix isn't a good deal.

There used to be at least one chemical stripper for the poyimide wire (worked great) but given its health and environmental concerns I would strongly avoid it (now wish I had as well).

Thanks
-Antonio

Tell me, please, I will use a mask. :D
 
Because through the pores, you lose insulation, moist air has a breakdown voltage of about 900 V.

Glass ε > 4 , uralane has a dielectric constant similar to Teflon, so the mix isn't a good deal.

Tell me, please, I will use a mask. :D

Yes moist air is a problem but it will be a problem with any material and increases as ε approaches 1.
Why does the glass and thinner have to matched dielectric constants?

I still have some of the stripper but not sure if the bottles are still labelled with pn and mfgr (20 years old). I can check tonight and that will give me a full day to think about giving you hazardous material info (someone needs to look out for you).

Thanks
-Antonio
 
We had some stripper in the navy that would remove epoxy and any thing else it touched. It was a yellow/green slimy compound.

Tell me its name, please.

Yes moist air is a problem but it will be a problem with any material and increases as ε approaches 1.

Not if you do the windings as I do, look at post#59.

Why does the glass and thinner have to matched dielectric constants?

The electric field "see" different dielectric constants, then there is no a homogeneous field, then capacitance will be not homogeneous.

I still have some of the stripper but not sure if the bottles are still labelled with pn and mfgr (20 years old). I can check tonight and that will give me a full day to think about giving you hazardous material info (someone needs to look out for you).

Thanks
-Antonio

Well, if classified information is fine, if you can pass me by PM. ;)
 
Most of the rail is cut. I need to remove the rivets from another section to finish the rest of the peices.
 

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