Bobbin wire can be bought here locally.
The mandrels, we custom machine them
The CNC machine is company's property.
The bobbins, we make them ourselves, they are flangeless. You don't have to use a readily made plastic bobbin.
The interlayer Nomex insulation, we order it. It's quite expensive.
A nice household alternative is the kitchen cooking paper sold in almost every supermarket. It's paper impregnated with something like sillicon. It's not hygroscopic like ordinary paper and has quite high breakdown voltage, the problem is it doesn't stick to anything. It's dielectric constant is higher than the Nomex's though.
For power transformers, presspan-polyester insulation is often used and it's great. We order that too.
The mandrels, we custom machine them
The CNC machine is company's property.
The bobbins, we make them ourselves, they are flangeless. You don't have to use a readily made plastic bobbin.
The interlayer Nomex insulation, we order it. It's quite expensive.
A nice household alternative is the kitchen cooking paper sold in almost every supermarket. It's paper impregnated with something like sillicon. It's not hygroscopic like ordinary paper and has quite high breakdown voltage, the problem is it doesn't stick to anything. It's dielectric constant is higher than the Nomex's though.
For power transformers, presspan-polyester insulation is often used and it's great. We order that too.
Thank you.
Here I can buy magnet wire & trought ebay I can buy a winding winder machine. No problem to make my own mandrels but how do you do and with material you make the bobbins.
I see some people in Spanish forums using the same paper with adhesive used by the house painters?
Have you tried cyanoacrylate like loctite or other similar instant glue for the oven cooking paper?
I listened Nomex before, but it's the best time I listen presspan-polyester, each day I learn a little more with you guys.
Here I can buy magnet wire & trought ebay I can buy a winding winder machine. No problem to make my own mandrels but how do you do and with material you make the bobbins.
I see some people in Spanish forums using the same paper with adhesive used by the house painters?
Have you tried cyanoacrylate like loctite or other similar instant glue for the oven cooking paper?
I listened Nomex before, but it's the best time I listen presspan-polyester, each day I learn a little more with you guys.
I have a double c-core, total iron area 1,5 x 2 inch from old Lenkurt switching power supplies. No idea about the quality of the iron. But i didnt design for 3 K ohm but 1,9
K
1920 primary and 120 secundary, and sort of symmetric so this transformer shoud be useful for PP .
K
1920 primary and 120 secundary, and sort of symmetric so this transformer shoud be useful for PP .
A nice way to do a quick flangless bobbin is to fold a piece of thick Nomex or a Nomex-polyester sandwich over the mandrel. The problem is, thick sheets will have a hard time bending over the sharp 90deg turns of the mandrel.
A trick to help the piece fold precisely over the angles of the mandrel, the sheet is put on a flat surface and lines where the foldings will be are pre-scratched using a sharpie knife. Some practice is needed to adjust your hand pressure. You must be careful no to scratch too deep, or you'll cut the sheet. The mandrel can be used as the template
Afterwards, the scratched sheet of nomex is easily folded over the mandrel. Its scratched edges will be a weak spot for breakdown voltage resistance, so it's a good idea to "fortify" the bobbin with rolling a few layers of some thinner insulation over it. It will also make the edges rounder and that is a good thing for the first winding. 🙂
Another messy and smelly way is to take cotton cloth or glass fibers and roll on the mandrel impregnating the cloth with polyester resin. Of course, something thin should be put on the mandrel first, such as a a thin sheet of nylon. This is messy, dirty and toxic if you don't have adequate ventilation and breathing protection and you'll have to wait until the resin cures. It results in really strong bobbins though.
I haven't tried cyanoacrylate glue but I'm skeptic, because I've read somewhere of its low shelf life.
I'm using contact cement, but it's tricky. You must not wait until it dries completely.
A trick to help the piece fold precisely over the angles of the mandrel, the sheet is put on a flat surface and lines where the foldings will be are pre-scratched using a sharpie knife. Some practice is needed to adjust your hand pressure. You must be careful no to scratch too deep, or you'll cut the sheet. The mandrel can be used as the template
Afterwards, the scratched sheet of nomex is easily folded over the mandrel. Its scratched edges will be a weak spot for breakdown voltage resistance, so it's a good idea to "fortify" the bobbin with rolling a few layers of some thinner insulation over it. It will also make the edges rounder and that is a good thing for the first winding. 🙂
Another messy and smelly way is to take cotton cloth or glass fibers and roll on the mandrel impregnating the cloth with polyester resin. Of course, something thin should be put on the mandrel first, such as a a thin sheet of nylon. This is messy, dirty and toxic if you don't have adequate ventilation and breathing protection and you'll have to wait until the resin cures. It results in really strong bobbins though.
I haven't tried cyanoacrylate glue but I'm skeptic, because I've read somewhere of its low shelf life.
I'm using contact cement, but it's tricky. You must not wait until it dries completely.
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Impedance doesn't really matter. Applied voltage matters. 1.9K instead of 3K would just mean that 200V rms would be 21W in your case. If 21W into 1.9K is your target it would be not be different from 13W into 3K. So need to use a good C-core. More power, or better more voltage, would require more turns.
For PP operation you will get about 4X power handling, with zero DC bias.
I get them from a friend of mines that makes transformers for other applications.
I have just bought some Hi-B C-cores from Nicore. The quality appears to be excellent from my first assessment and price as well. The only problem is the high shipping cost....
We don't use EI, but C-core and M-type of lamination sometimes. Check Waasner, they have great stuff. Their cut cores are well polished.
I have no idea, to be honest. A local audiophile colleague ordered an extremely big C-core from himself with an ambition for a GU81 SE amp, but I'm not sure if the order was private or through a company.
Hey there. I ordered parts to build an experimental CCS to deliver DC current to the primary for the measurement purposes, they should arrive in a week.
I have everything else - low THD SS amplifier, and THD measurement using EMU0404.
I also managed to wind the second transformer. Still haven't measured it for the "OPT curse, that means a secondary layer with a turn less or more. It happened when I wound my first transformer and even if I measured more than 20 transformers afterwards with flawless results, it still gives me chills. 😀
I have everything else - low THD SS amplifier, and THD measurement using EMU0404.
I also managed to wind the second transformer. Still haven't measured it for the "OPT curse, that means a secondary layer with a turn less or more. It happened when I wound my first transformer and even if I measured more than 20 transformers afterwards with flawless results, it still gives me chills. 😀
I'm ashamed to say I still have not found spare time to work on my current source due to the lack of spare time.
If someone insists, I can measure the THD without DC current, but this is not realistic.
If someone insists, I can measure the THD without DC current, but this is not realistic.
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