"Patrick Turner" wrote in message
...


Shiva wrote:

"Patrick Turner" wrote in message
...


Steve Kendall wrote:

I am planning to DIY output transformers for my future push pull
power
amplifier. After a few days search on the net, I can only find one
place to sell EI laminations and another one to sell toroidal core
in
small quantity. Since the company selling EI laminations only offers
EI-112 and the price is high, so I decide to stick to toroidal core.

My first question is: can I use a toroidal core made by grain
oriented
silicon steel to make a good PP output transformer?

My second question is: if yes to Q1, then how to wind the toroidal
core to keep the leak inductance and shunt capacitance minimum?

If slight mismatch between output tubes makes the toroidal core
saturate fast so that it can't be used in PP applicaiton, then can I
at least use toroidal output transformer in a parafeed application?

Thanks!

Before we might waste time advising you through your R&D process,
how do you propose to place neat and tightly wound turns onto the
core?
Most people use a special machine, so have you got one,
if not, then how would you wind it?

Patrick Turner.

With a shuttle? Sorry. Anyhow, doughnuts are wound by hand all the
time,
it's pretty tedious but straight-forward. Mind you, I've only *un*
wound
them myself (to change the ratio), but it seems really doable,
especially if
you're laying multiple sections...

With a bleedin shuttle.
I use a piece of 3/4" plastic conduit, with slots each end,
and its length is one turn long. Pile on the wire, as much as can be
fitted, then spend days trying to be neat and tidy with the wire.
Its ghard to keep track of the turns, and one has to put joins in
along the way.
Insulation is with tape, easy, but slow, but it too has to be just right.
And impregnation must be with a vacuum chamber, because the
varnish or wax just won't run inside with soaking, so I have found,
unless the insulation tape is a mesh tape, and I don't like insulation
with
lots of holes in it.
I have done a few power trannies like this, but OPTs need
3 times the turns, and it all is a real PITA.

Its really hard to figure where to put the turns, and have them all lay up
without
crossing over wires, since that's where a short will occur later with a
toroid.

I tried to interest a local custom winder to wind me up
some toroidal OPTs, and when I showed him the taps and layers I wanted, he
went pale, and vomited all over me as he collapsed.
And he has the right machines, and has made lotsa mullah from trannies.


Bwah!!! This reminds me of many run-ins with machine shops, where I would
explain to the guy what i think would be a trivial job for him, and he'd
look at me with that "are you insane or just f8ckin' with me?" look... Soon
the greeting where "Whatthef8ckisit *NOW*?" BTW, i do agree with you on
almost everything you said...
-dim

ust wind my own E&I trannies.
It does mean I have to buy at least 50Kg of core material at
a time, but the GOSS I get is extremely good low loss material,
and has losses almost identical to good toroidals.
At 0.8 Tesla, the iron U is 17,000.

Plitron make good toroidals. No need to wind one's own if you really want
a
toroid.

Patrick Turner.