North American Ferrite core supplier for prototypes

[Spehro Pefhany]

http://www.neosidcanada.com/company.htm

One time they cut and ground me few pieces for a custom job. Very
approachable. None of this " And how many million will you be planning to
purchase from us in the future"

Was that recently, Boris?


Best regards,
Spehro Pefhany

 

[Joerg]

Hello Spehro,

I think it's one of those retro things. The board is clearly
contemporary, though a deliberate choice has been made to use
through-hole parts.

Yes, like the PT Cruiser. I am more of a purist when it comes to tubes
and other oldie designs. Only components from the era. When there was no
choice I tried hiding modern stuff, especially in restoration projects.
One of the radios still contained a Ducati capacitor even though their
biz moved to motorcycles decades before. Hidden inside was a new Philips
cap.

Regards, Joerg

 

[Pooh Bear]

I think they're more than friendly to transformer winders, not to
engineers.


Small. I have some RM6 44 that will probably do but they're a touch
taller than I'd like. Here's a photo of a cute little gapped EE core
transformer that does about what I want to do:

http://www.speff.com/flyback_converter.jpg

Power is only about 25mW at 50-100kHz (discontinuous mode flyback).
Must be a lot of leakage inductance with that split bobbin. It's taped
and all glopped over with conformal coating, so the core is smaller
than it looks.

Do you need the split bobbin for safety ? With small cores margins take up too
much room. Using triple insulated wire make more sense.

Graham

 

[Spehro Pefhany]

Do you need the split bobbin for safety ? With small cores margins take up too
much room. Using triple insulated wire make more sense.

Graham

Lower capacitive coupling between the windings is the main reason for
the split bobbin.


Best regards,
Spehro Pefhany

 

[Pooh Bear]

Lower capacitive coupling between the windings is the main reason for
the split bobbin.

Do you need one in your case though ? Split bobbins can be hard to find.

Graham

 

[Tony Williams]

[Newark]

They're better on Ferroxcube- 17 days lead time and minimum oder
1 piece (and no stock shown, but probably they're drawing on
Farnell, as you suggest).

The Farnell cat show a wide range of ferrite cores
in stock, from Ferroxcube and Epcos. Quite a few
low-profile possibilities (4-8mm) from both, either
as low-profile RM or E-E cores. Can't see any split
bobbins though.

 

[Boris Mohar]

Was that recently, Boris?

No, actually it was about six years ago.

 

[Joerg]

Hello Graham,

Do you need one in your case though ? Split bobbins can be hard to find.

At Kaschke that is a regular catalog item, at least for pot cores.

Regards, Joerg

 

[Sergey Kubushin]

Hello Graham,


At Kaschke that is a regular catalog item, at least for pot cores.

BTW, does anybody know where I can buy small amount of _transformer steel_
EI lamination? Its not such a difficult thing to find ferrite, iron powder
or similar core but I can't find transformer steel anywhere... I want to
wind several (4-8) _output_ transformers for tube amplifiers. I can't find
any ready-made transformers that suit my needs and all those custom-wound
ones are helluva expensive. I would've even try to rewind some surplus ones
but they are all varnished that makes such a task next to impossible (

 

[Joerg]

Hello Sergey,

BTW, does anybody know where I can buy small amount of _transformer steel_
EI lamination? ...

Other than buying a few cheap transformers and taking them apart I
wouldn't know off hand. That is usually how I did it. You could start a
separate thread about it so more people would see it.

Regards, Joerg

 

[Spehro Pefhany]

Hello Sergey,


Other than buying a few cheap transformers and taking them apart I
wouldn't know off hand. That is usually how I did it. You could start a
separate thread about it so more people would see it.

Carpenter is one of the big guys, but steel suppliers are a major PITA
to deal with. A few years ago it was a $500 minimum, probably more
now. Maybe you can sweet-talk them into giving you some samples.

Many years ago some outfit in the UK had transformer "kits" with the
primary pre-wound, you just have to add the secondary. Don't know if
they're still available. I bought a few from Maplin.


Best regards,
Spehro Pefhany

 

[Joerg]

Hello Spehro,

Many years ago some outfit in the UK had transformer "kits" with the
primary pre-wound, you just have to add the secondary. Don't know if
they're still available. I bought a few from Maplin.

That was also one of the advantages of taking apart existing
transformers. Preferably some with lower voltage secondaries because it
was less work to unwind those. Then you had the primary already there,
120V/240V taps and all.

But Sergey wants to create tube amp output transformers and that would
almost certainly require a complete rewind. Unless one would find the
perfect match where the primary shows just the desired impedance and a
120/240 split if he has to design push-pull.

If I were in his shoes I'd seriously consider one of the hi-perm
ferrites. Preferably some huge pot core for easier winding. These
materials have come a long way since the days of tube amps. I believe
you could get a lot more fidelity out of them. Also, the round bobbins
allow to fix them to an electric drill chuck and wind'em up at slow
speed. I never really succeeded doing that with square bobbins but in
those days the only way to slow down a drill was via a variable
transformer and then it would sputter at very low speeds.

Regards, Joerg

 

[Zak]

One of the radios still contained a Ducati capacitor even though their
biz moved to motorcycles decades before. Hidden inside was a new Philips
cap.

There are/were recently still caps being made under the Ducati name. See
http://www.baco-army-goods.nl/condensator pag-1.htm
for surplus 400 volt AC caps with VDE mark


Thomas

 

[Joerg]

Hello Thomas,

There are/were recently still caps being made under the Ducati name. See
http://www.baco-army-goods.nl/condensator pag-1.htm
for surplus 400 volt AC caps with VDE mark

Interesting. And they state that it is from current production runs, not
old stock. It looks like it is from Ducati-Energia. I don't know about
how the companies are linked these days but they are in Bologna just
like the motorcycle manufacturer. Plus there are lots of other products
under that name, parfumes etc.

Regards, Joerg

 

[Pooh Bear]

BTW, does anybody know where I can buy small amount of _transformer steel_
EI lamination? Its not such a difficult thing to find ferrite, iron powder
or similar core but I can't find transformer steel anywhere... I want to
wind several (4-8) _output_ transformers for tube amplifiers. I can't find
any ready-made transformers that suit my needs and all those custom-wound
ones are helluva expensive. I would've even try to rewind some surplus ones
but they are all varnished that makes such a task next to impossible (

The E-I laminations used in a power transformer aren't ideal for an audio
output transformer of any fidelity.

The laminations in an audio output transformer should be thinner ( higher
frequency eddy current losses ) and ISTR that the preferred matereial grade
differs too.

That probably explains the higher costs ( not to mention small quantities ).

You might fare better with a toroidal core ( thinner material anyway and I
think it's generally higher quality ). You'll need more turns/Volt than at
power line frequency too since you'll want the thing to work down to 20Hz I
assume.

Graham

 

[Fred Bloggs]

Any suggestions for a North American supplier with a good online
presence? Tiny to large E/RM/Pot core etc.

I have used these people for prototype quantities, they are
knowledgeable and responsive, and the products are solid and ready to
mount. Why wind it yourself?

http://www.coilws.com/

 

[Tony Williams]

The E-I laminations used in a power transformer aren't ideal for
an audio output transformer of any fidelity.
The laminations in an audio output transformer should be thinner
( higher frequency eddy current losses ) and ISTR that the
preferred matereial grade differs too.

The famous Williamson audio amplifier specified the
use of "dynamo grade laminations". Iron losses were
not seen as a problem for power output transformers
and 0.015" lams in 4% silicon steel were often used.

Low level transformers would need the higher permeability
provided by nickel-iron cores (to avoid excessive turns
count), and probably using thinner laminations.

You might fare better with a toroidal core ( thinner material
anyway and I think it's generally higher quality ). You'll need
more turns/Volt than at power line frequency too since you'll
want the thing to work down to 20Hz I assume.

The biggest problem with a lamination transformer
at audio frequencies was the hf rolloff due to the
leakage inductance. Toroidal transformers send
most of that problem away.

 

[Joerg]

Hello Tony,

The biggest problem with a lamination transformer
at audio frequencies was the hf rolloff due to the
leakage inductance. Toroidal transformers send
most of that problem away.

While I also prefer toroids, the large number of turns required for a
tube output transformer would entice me to use a pot core with bobbin in
this case.

Regards, Joerg

 

[Pooh Bear]

Hello Tony,


While I also prefer toroids, the large number of turns required for a
tube output transformer would entice me to use a pot core with bobbin in
this case.

You'ld need something rather larger than a pot core ! ;-)

Graham

 

[Joerg]

Hello Graham,

You'ld need something rather larger than a pot core ! ;-)

Depends on the power and DC load. There are pot cores where you almost
need a small crane to install them ;-)

Regards, Joerg