[Patrick Turner]

You guys can rattle your sabres at each other about all the off charter
postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place with
regard to
tube discussions.

Whenever I drop in to read a few posts at highly moderated groups,
I tend to fall asleep because they have sich dismal levels of technical
activity and communications.


The Internet is MAINSTREAM now and not the preserve of elite minds at
universities
or military establishments.
What was once a hallowed priveligded place accessible
only by the few with computer skills and who could afford a PC has now
been taken by the people to the people
and for the people, enabled mainly by the plummeting price of hardware
and improved software.
I knew someone who spent $25,000 on a PC in 1984, ( in today's $$, it
was a fortune ).
And amoung all people who have come to discuss things there are the
inevitable mobs of the unruly
who'd hang anyone on a whim, and tear ppl apart like bored silly dogs
tearing clothes of a clothesline, and contribute banality and BS ike it
was gospel.

Many would never find a friend away from their keyboard.

I am mainly here for the ON charter postings, but since I would claim
to be at least slightly broad minded, I engage in some off topic
conversations
when technical matter discussions have subsided to a low level.

But the myriad of postings where blokes do nothing except labour
hard at saying why someone is an AH or whatever don't much interest me.

If one goes for a bicycle ride, there is plenty one likes to see, and
likes not to see.
I like to get away from the heavy traffic to be amoung nature and what
interests me is the absense
of mankind's obviously noxious interactions.
I never expect a whole journey on a bicycle to be perfect, or completely
free of nervous moments when I share roads with motorists.

I don't expect an ideal world out there when I step out the door on bike
ride.
When I see the ducks waddling by the lake's edge, I know they are food
for the foxes.
Nature is beautiful, but life and death is ruled by tooth and claw,
and calamitous violence.
Probably hundreds of foxes get run over by cars each year just in NSW.

So it is with the Internet. I don't expect it to be a perfect place with
perfect behaviour. Blokes say "boo" to each other all day long and never
tire of it.
Expecting perfection is like expecting a fox to be nice to a duck about
to become its dinner.
Pigs will grow wings and fly before the Internet gets any "better".


There are far worse places to try to talk to ppl on the Net.


Try soc.men for example. Wall to wall BS and angst. Seems like every
socially maladjusted man or woman hangs out there to wage war there with
words.

I could say the range of maladjusted ppl here at r.a.t is quite
tolerable
compared to elsewhere, and where some oddness or quirkiness or downright
rudeness
appears daily, it doesn't really bother me; its a lot less than
elsewhere.

I ain't here to control anyone. I do like farnarkling around
with tubes and I make a living doing it for people
who appreciate the technology.
I will never get rich using a soldering iron, or fussing about anode
conditions
and output trannies but I feel a need to keep my mind sharp
by sharing my interest with the few genuinely interested.
In my city of 330,000 souls, there are very few with whom I can discuss
the technical ideas behind making audio gear. Some here ask me awkward
questions
and it keeps me on my toes to give an answer.

Most of the guys who really did know a lot about tubecraft from the past
have retired expired or died before they bought a PC.
Most of that old generation were not very communicative, and stuck in
their old ways,
or didn't have the time to learn to type to others around the world.

I am lucky I think to have discovered the Net before I turned old and
sour,
and lucky that I enjoy it, and lucky that I have met so many
fine minds and ideas along the way.

One doesn't find any gemstones or nuggets of gold unless
you work at digging big holes and shifting dirt and rocks.
One needs to be skilled with spade and shovel, and have stout waterproof
boots.
These are handy for digging one's way through layers of BS at times.

Regards to all,

Patrick Turner.

[mick]

On Thu, 22 Nov 2007 14:45:21 +0000, Patrick Turner wrote:

You guys can rattle your sabres at each other about all the off charter
postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place with
regard to
tube discussions.

snip


Perhaps you could enlighten me a bit then?

I have a pair of, what I think are fairly cheap OPTs for SE EL84s. They
look to be quite well assembled though, with fairly thin laminations. The
lams are 65mm x 55mm in about a 21mm stack. I can't really tell 'cos they
are bolted down at the moment. I'm assuming that the central core is
about square.

It looks as if they don't have interleaved windings. In your opinion,
would it be worth my while stripping them down and rebuilding them or
would this probably be a waste of time on a core this size? I would like
to include a CFB winding on them - probably about 10-12% (is that by
turns or by Z?). Of course, while I'm doing this I could add some
interleaving.

The idea is to use them with SET (strapped tetrodes or DHT) and CFB. I'm
not expecting them to magically become brilliant - passable would do!
Primary DC would be about 60mA - probably about what they were designed
for.

I'm considering putting some temporary turns round the existing windings
(there's room), putting some AC on the primary and getting a "turns per
volt" figure that I can use to calculate the turns figures when
rebuilding. Would that make sense?

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[Jon Yaeger]

in article , mick at
lid wrote on 11/22/07 10:59 AM:

On Thu, 22 Nov 2007 14:45:21 +0000, Patrick Turner wrote:

You guys can rattle your sabres at each other about all the off charter
postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place with
regard to
tube discussions.

snip


Perhaps you could enlighten me a bit then?

I have a pair of, what I think are fairly cheap OPTs for SE EL84s. They
look to be quite well assembled though, with fairly thin laminations. The
lams are 65mm x 55mm in about a 21mm stack. I can't really tell 'cos they
are bolted down at the moment. I'm assuming that the central core is
about square.

It looks as if they don't have interleaved windings. In your opinion,
would it be worth my while stripping them down and rebuilding them or
would this probably be a waste of time on a core this size? I would like
to include a CFB winding on them - probably about 10-12% (is that by
turns or by Z?). Of course, while I'm doing this I could add some
interleaving.

The idea is to use them with SET (strapped tetrodes or DHT) and CFB. I'm
not expecting them to magically become brilliant - passable would do!
Primary DC would be about 60mA - probably about what they were designed
for.

I'm considering putting some temporary turns round the existing windings
(there's room), putting some AC on the primary and getting a "turns per
volt" figure that I can use to calculate the turns figures when
rebuilding. Would that make sense?



While you wait for Prof. Turner to reply . . .

Something to consider? I've found that some of these small OPTs are perfect
for headphone amplifiers, i.e. the SET variety. I designed a very decent
headphone amp around parts salvaged from a Wollensak Tape recorder.

I assume your trannies are already condifured for SE? If P/PO, you'll have
to rearrange the lams, of course.

You may or may not get an outcome that is worth your time, but in this
respect these seem like excellent trannies to experiment with. If you get
them to work, you have learned something. If not, it's no big (financial)
loss.

Jon

[mick]

On Thu, 22 Nov 2007 11:24:11 -0500, Jon Yaeger wrote:

in article , mick at
lid wrote on 11/22/07 10:59 AM:

On Thu, 22 Nov 2007 14:45:21 +0000, Patrick Turner wrote:

You guys can rattle your sabres at each other about all the off
charter postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place
with regard to
tube discussions.

snip


Perhaps you could enlighten me a bit then?

I have a pair of, what I think are fairly cheap OPTs for SE EL84s. They
look to be quite well assembled though, with fairly thin laminations.
The lams are 65mm x 55mm in about a 21mm stack. I can't really tell
'cos they are bolted down at the moment. I'm assuming that the central
core is about square.

It looks as if they don't have interleaved windings. In your opinion,
would it be worth my while stripping them down and rebuilding them or
would this probably be a waste of time on a core this size? I would
like to include a CFB winding on them - probably about 10-12% (is that
by turns or by Z?). Of course, while I'm doing this I could add some
interleaving.

The idea is to use them with SET (strapped tetrodes or DHT) and CFB.
I'm not expecting them to magically become brilliant - passable would
do! Primary DC would be about 60mA - probably about what they were
designed for.

I'm considering putting some temporary turns round the existing
windings (there's room), putting some AC on the primary and getting a
"turns per volt" figure that I can use to calculate the turns figures
when rebuilding. Would that make sense?



While you wait for Prof. Turner to reply . . .

Something to consider? I've found that some of these small OPTs are
perfect for headphone amplifiers, i.e. the SET variety. I designed a
very decent headphone amp around parts salvaged from a Wollensak Tape
recorder.

I assume your trannies are already condifured for SE? If P/PO, you'll
have to rearrange the lams, of course.

You may or may not get an outcome that is worth your time, but in this
respect these seem like excellent trannies to experiment with. If you
get them to work, you have learned something. If not, it's no big
(financial) loss.


Yes, these are already SE transformers. I must admit that I hadn't
considered using them for headphones - that raises yet another
possibility!

As you say, it's no great financial loss if I mess them up - they are my
main OPTs at the moment though and are liable to remain that way until
after Christmas at least! I doubt if I will get round to rewinding them
yet though.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[Jon Yaeger]

in article , mick at
lid wrote on 11/22/07 2:19 PM:

On Thu, 22 Nov 2007 11:24:11 -0500, Jon Yaeger wrote:

in article , mick at
lid wrote on 11/22/07 10:59 AM:

On Thu, 22 Nov 2007 14:45:21 +0000, Patrick Turner wrote:

You guys can rattle your sabres at each other about all the off
charter postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place
with regard to
tube discussions.

snip


Perhaps you could enlighten me a bit then?

I have a pair of, what I think are fairly cheap OPTs for SE EL84s. They
look to be quite well assembled though, with fairly thin laminations.
The lams are 65mm x 55mm in about a 21mm stack. I can't really tell
'cos they are bolted down at the moment. I'm assuming that the central
core is about square.

It looks as if they don't have interleaved windings. In your opinion,
would it be worth my while stripping them down and rebuilding them or
would this probably be a waste of time on a core this size? I would
like to include a CFB winding on them - probably about 10-12% (is that
by turns or by Z?). Of course, while I'm doing this I could add some
interleaving.

The idea is to use them with SET (strapped tetrodes or DHT) and CFB.
I'm not expecting them to magically become brilliant - passable would
do! Primary DC would be about 60mA - probably about what they were
designed for.

I'm considering putting some temporary turns round the existing
windings (there's room), putting some AC on the primary and getting a
"turns per volt" figure that I can use to calculate the turns figures
when rebuilding. Would that make sense?



While you wait for Prof. Turner to reply . . .

Something to consider? I've found that some of these small OPTs are
perfect for headphone amplifiers, i.e. the SET variety. I designed a
very decent headphone amp around parts salvaged from a Wollensak Tape
recorder.

I assume your trannies are already condifured for SE? If P/PO, you'll
have to rearrange the lams, of course.

You may or may not get an outcome that is worth your time, but in this
respect these seem like excellent trannies to experiment with. If you
get them to work, you have learned something. If not, it's no big
(financial) loss.


Yes, these are already SE transformers. I must admit that I hadn't
considered using them for headphones - that raises yet another
possibility!

As you say, it's no great financial loss if I mess them up - they are my
main OPTs at the moment though and are liable to remain that way until
after Christmas at least! I doubt if I will get round to rewinding them
yet though.


If you are interested, I'll e-mail you a copy of the headphone amp design.

Jon

[mick]

On Thu, 22 Nov 2007 19:02:21 -0500, Jon Yaeger wrote:

snip

If you are interested, I'll e-mail you a copy of the headphone amp
design.


That would be appreciated - it gives me another possible option!
Use: mick[AT]mixtel.co.uk as I check that one most often.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[Patrick Turner]

mick wrote:

On Thu, 22 Nov 2007 14:45:21 +0000, Patrick Turner wrote:

You guys can rattle your sabres at each other about all the off charter
postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place with
regard to
tube discussions.

snip

Perhaps you could enlighten me a bit then?

I have a pair of, what I think are fairly cheap OPTs for SE EL84s. They
look to be quite well assembled though, with fairly thin laminations. The
lams are 65mm x 55mm in about a 21mm stack. I can't really tell 'cos they
are bolted down at the moment. I'm assuming that the central core is
about square.

It looks as if they don't have interleaved windings. In your opinion,
would it be worth my while stripping them down and rebuilding them or
would this probably be a waste of time on a core this size? I would like
to include a CFB winding on them - probably about 10-12% (is that by
turns or by Z?). Of course, while I'm doing this I could add some
interleaving.

The idea is to use them with SET (strapped tetrodes or DHT) and CFB. I'm
not expecting them to magically become brilliant - passable would do!
Primary DC would be about 60mA - probably about what they were designed
for.

I'm considering putting some temporary turns round the existing windings
(there's room), putting some AC on the primary and getting a "turns per
volt" figure that I can use to calculate the turns figures when
rebuilding. Would that make sense?

I did all the possible tweaks I could on a pair of SE EL84 amps
in a stereo AM radio in 1993, when I became seriously interested in
audio gear.

The existing OPT were about the same as you have but with one anode
primary
wound over the top of one lousy 16 ohm secondary.

I had an amount of wire slightly less dia than the existing secondary
wire size, and there was room to wind a layer or two extra
over the top of the primary by mwans of threading wire through between
core and coil,
and it took awhile to fill a layer with the thicker secondary wire size,
but
I was able to do it OK.

This extra winding of similar turns to the existing sec was connected in
series with the
existing sec, with speaker connected off the existing 16 ohm winding.
The two seriesed windings of thick wire were used to provide CFB and
speaker output.
The amount of voltage applied to the cathode is approx 8% of the
possible 200Vrms between anode and cathode.

The simplest way to consider CFB is in % of total winding turns passing
anode current.

Some where between at least 8% and a max of 25% for EL84 is fine.

If you choose to rewind the OPT, its a major job. Better is to just wind
new ones.
Its not all that hard, but you will some laminations taken from some old
transformers
you'd have to find and strip down. Or else buy a pair of 20VA mains E&I
trannies from
Radio shack, and strip them down entirely, throw all the wire and
plastic bobbin away after chiseling it off the core.

The core leg should be 25mm stack x 25mm tongue,
and then you will need to find some wire, about 0.2mm dia will maybe do
for the primary.
The secondary proably will be 0.6mm wire.
There needs to be at least two sec sections with anode and anode P
sections sandwiched between S sections.
Random winding the wire is fine as long as you traverse the winding
slowly and
keep the wire build up level and you know how to insulate.

I am being very rough in my advice here and I don't plan to design all
the
details of your amp and OPT for you.
I make the point that there is a lot you have to do to get from A to B,
and its up to you if you either want to reproduce the junk standards of
1960,
or make something you can be proud of.

YOU should do all that YOURSELF by reading my website about winding SET
OPT
and learning the 3,269 steps and other items you will need to understand
before
winding anything. What you might learn begins to make sense when you
begin testing your
circuit. Or it doesn't make sense and you'll start all over again.

Most ppl give up at this stage, its far too hard, and they go to Hammond
for an OPT fix.

Anyway, my 5 watt SE amps with their CFB and some global NFB turned out
very well
and sounded fine with sensitive speakers. I learnt a lot, and didn't
need to
go to hammond.
I have since re-wound a few OPT that were fused open in other radios I
have serviced.
Its not uncommon for the primary wire to be 0.1mm or 0.15mm dia, and
this gets hot and goes open if a
short circuit in a tube occurs, likely when an EL84 dies, and of course
the
1960 radio companies never installed 100mA fuses between cathode and 0V.

Patrick Turner.




--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[mick]

On Fri, 23 Nov 2007 13:13:38 +0000, Patrick Turner wrote:

mick wrote:

On Thu, 22 Nov 2007 14:45:21 +0000, Patrick Turner wrote:

You guys can rattle your sabres at each other about all the off
charter postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place
with regard to
tube discussions.

snip

Perhaps you could enlighten me a bit then?

I have a pair of, what I think are fairly cheap OPTs for SE EL84s. They
look to be quite well assembled though, with fairly thin laminations.
The lams are 65mm x 55mm in about a 21mm stack. I can't really tell
'cos they are bolted down at the moment. I'm assuming that the central
core is about square.

It looks as if they don't have interleaved windings. In your opinion,
would it be worth my while stripping them down and rebuilding them or
would this probably be a waste of time on a core this size? I would
like to include a CFB winding on them - probably about 10-12% (is that
by turns or by Z?). Of course, while I'm doing this I could add some
interleaving.

The idea is to use them with SET (strapped tetrodes or DHT) and CFB.
I'm not expecting them to magically become brilliant - passable would
do! Primary DC would be about 60mA - probably about what they were
designed for.

I'm considering putting some temporary turns round the existing
windings (there's room), putting some AC on the primary and getting a
"turns per volt" figure that I can use to calculate the turns figures
when rebuilding. Would that make sense?

I did all the possible tweaks I could on a pair of SE EL84 amps in a
stereo AM radio in 1993, when I became seriously interested in audio
gear.

The existing OPT were about the same as you have but with one anode
primary
wound over the top of one lousy 16 ohm secondary.

I had an amount of wire slightly less dia than the existing secondary
wire size, and there was room to wind a layer or two extra over the top
of the primary by mwans of threading wire through between core and coil,
and it took awhile to fill a layer with the thicker secondary wire size,
but
I was able to do it OK.

This extra winding of similar turns to the existing sec was connected in
series with the
existing sec, with speaker connected off the existing 16 ohm winding.
The two seriesed windings of thick wire were used to provide CFB and
speaker output.
The amount of voltage applied to the cathode is approx 8% of the
possible 200Vrms between anode and cathode.

The simplest way to consider CFB is in % of total winding turns passing
anode current.

Some where between at least 8% and a max of 25% for EL84 is fine.

If you choose to rewind the OPT, its a major job. Better is to just wind
new ones.
Its not all that hard, but you will some laminations taken from some old
transformers
you'd have to find and strip down. Or else buy a pair of 20VA mains E&I
trannies from
Radio shack, and strip them down entirely, throw all the wire and
plastic bobbin away after chiseling it off the core.

The core leg should be 25mm stack x 25mm tongue, and then you will need
to find some wire, about 0.2mm dia will maybe do for the primary.
The secondary proably will be 0.6mm wire. There needs to be at least two
sec sections with anode and anode P sections sandwiched between S
sections. Random winding the wire is fine as long as you traverse the
winding slowly and
keep the wire build up level and you know how to insulate.

I am being very rough in my advice here and I don't plan to design all
the
details of your amp and OPT for you.
I make the point that there is a lot you have to do to get from A to B,
and its up to you if you either want to reproduce the junk standards of
1960,
or make something you can be proud of.

YOU should do all that YOURSELF by reading my website about winding SET
OPT
and learning the 3,269 steps and other items you will need to understand
before
winding anything. What you might learn begins to make sense when you
begin testing your
circuit. Or it doesn't make sense and you'll start all over again.

Most ppl give up at this stage, its far too hard, and they go to Hammond
for an OPT fix.

Anyway, my 5 watt SE amps with their CFB and some global NFB turned out
very well
and sounded fine with sensitive speakers. I learnt a lot, and didn't
need to
go to hammond.
I have since re-wound a few OPT that were fused open in other radios I
have serviced.
Its not uncommon for the primary wire to be 0.1mm or 0.15mm dia, and
this gets hot and goes open if a
short circuit in a tube occurs, likely when an EL84 dies, and of course
the
1960 radio companies never installed 100mA fuses between cathode and 0V.



Thanks, Patrick. That's some useful information. I've had a look at your
web site several times, but I must admit that much of it hasn't sunk in
yet! :-)

I hadn't considered using 20VA mains trannies. I thought the lams
wouldn't be suitable. I might try that with one of the old ones that I
have kicking around.

Cheers.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[Patrick Turner]

mick wrote:

On Fri, 23 Nov 2007 13:13:38 +0000, Patrick Turner wrote:

mick wrote:

On Thu, 22 Nov 2007 14:45:21 +0000, Patrick Turner wrote:

You guys can rattle your sabres at each other about all the off
charter postings,
and indulge as much as you wish in mutual baiting of each other.

I avoid taking excessive notice of around 1,001 things worth ignoring
each day of my life.
Hence I ignore most posts at r.a.t.

Despite a terrible signal to noise ratio its the most vibrant place
with regard to
tube discussions.

snip

Perhaps you could enlighten me a bit then?

I have a pair of, what I think are fairly cheap OPTs for SE EL84s. They
look to be quite well assembled though, with fairly thin laminations.
The lams are 65mm x 55mm in about a 21mm stack. I can't really tell
'cos they are bolted down at the moment. I'm assuming that the central
core is about square.

It looks as if they don't have interleaved windings. In your opinion,
would it be worth my while stripping them down and rebuilding them or
would this probably be a waste of time on a core this size? I would
like to include a CFB winding on them - probably about 10-12% (is that
by turns or by Z?). Of course, while I'm doing this I could add some
interleaving.

The idea is to use them with SET (strapped tetrodes or DHT) and CFB.
I'm not expecting them to magically become brilliant - passable would
do! Primary DC would be about 60mA - probably about what they were
designed for.

I'm considering putting some temporary turns round the existing
windings (there's room), putting some AC on the primary and getting a
"turns per volt" figure that I can use to calculate the turns figures
when rebuilding. Would that make sense?

I did all the possible tweaks I could on a pair of SE EL84 amps in a
stereo AM radio in 1993, when I became seriously interested in audio
gear.

The existing OPT were about the same as you have but with one anode
primary
wound over the top of one lousy 16 ohm secondary.

I had an amount of wire slightly less dia than the existing secondary
wire size, and there was room to wind a layer or two extra over the top
of the primary by mwans of threading wire through between core and coil,
and it took awhile to fill a layer with the thicker secondary wire size,
but
I was able to do it OK.

This extra winding of similar turns to the existing sec was connected in
series with the
existing sec, with speaker connected off the existing 16 ohm winding.
The two seriesed windings of thick wire were used to provide CFB and
speaker output.
The amount of voltage applied to the cathode is approx 8% of the
possible 200Vrms between anode and cathode.

The simplest way to consider CFB is in % of total winding turns passing
anode current.

Some where between at least 8% and a max of 25% for EL84 is fine.

If you choose to rewind the OPT, its a major job. Better is to just wind
new ones.
Its not all that hard, but you will some laminations taken from some old
transformers
you'd have to find and strip down. Or else buy a pair of 20VA mains E&I
trannies from
Radio shack, and strip them down entirely, throw all the wire and
plastic bobbin away after chiseling it off the core.

The core leg should be 25mm stack x 25mm tongue, and then you will need
to find some wire, about 0.2mm dia will maybe do for the primary.
The secondary proably will be 0.6mm wire. There needs to be at least two
sec sections with anode and anode P sections sandwiched between S
sections. Random winding the wire is fine as long as you traverse the
winding slowly and
keep the wire build up level and you know how to insulate.

I am being very rough in my advice here and I don't plan to design all
the
details of your amp and OPT for you.
I make the point that there is a lot you have to do to get from A to B,
and its up to you if you either want to reproduce the junk standards of
1960,
or make something you can be proud of.

YOU should do all that YOURSELF by reading my website about winding SET
OPT
and learning the 3,269 steps and other items you will need to understand
before
winding anything. What you might learn begins to make sense when you
begin testing your
circuit. Or it doesn't make sense and you'll start all over again.

Most ppl give up at this stage, its far too hard, and they go to Hammond
for an OPT fix.

Anyway, my 5 watt SE amps with their CFB and some global NFB turned out
very well
and sounded fine with sensitive speakers. I learnt a lot, and didn't
need to
go to hammond.
I have since re-wound a few OPT that were fused open in other radios I
have serviced.
Its not uncommon for the primary wire to be 0.1mm or 0.15mm dia, and
this gets hot and goes open if a
short circuit in a tube occurs, likely when an EL84 dies, and of course
the
1960 radio companies never installed 100mA fuses between cathode and 0V.


Thanks, Patrick. That's some useful information. I've had a look at your
web site several times, but I must admit that much of it hasn't sunk in
yet! :-)

I hadn't considered using 20VA mains trannies. I thought the lams
wouldn't be suitable. I might try that with one of the old ones that I
have kicking around.

Many generic Taiwanese made mains trannies have quite reasonable
laminations.
its not top class grain oriented material, but not the poorest non
oriented silicon steel either.
Tranny makers mainly only make mains trannies and now use medium grade
material which is a balance between cost per kilogram,
and technical performance that is acceptable, ie, conforms to the lowest
common denominator
industry standards. Most I buy here in Oz are really made for 220Vac,
but here we commonly have 255V,
and this will make many transformers designed on the very edge of
acceptability run hotter and noiser
than is acceptable for use in hi-fi amplifiers.

So if you are desperate for laminations, strip old or new trannies
purchased only for the laminations.

So if you buy a mains transformer of say 20VA to 50VA rating, the cost
might be
$50, but this is cheap compared to trying to source a small quantity of
new made
laminations.
My Oz supplier Sankey Aust won't sell me less than 50Kg in a sale; they
are used to
selling many tonnes to their favoured customers.
The majority of cores are for large mains trannies.
So finding lams is difficult, and the time spent on the hunt costs and
you are just as well off
if you re-cycle some lams gained from some stripped down new/old tranny.

Often the trannies used for 30VA rated audio line transformers DO HAVE
GOSS lams in them,
and these are a fine source of lams for SE OPTs.

Since SE OPTs are gapped, the steel quality os not as critical as is
made out by many
experts because the air gapping drastically changes the way the core
functions in terms of
saturation, distortion, and permeability.

To make it easy to strip old/new transformers for re-use, I remove all
clamp yokes
and place the item in my open wood fire and heat until cherry red and
then allow to cool slowly.
The plastic and insulation coatings and varnish will be vaporized, and
just leave ash and lams will fall out into your hands.
Place the copper in the re-cycle bin.
TYhe heating won't hurt the magnetic properties.
If you live in a place without a fire place or backyard where you could
not use an old
five gallon tin with slots in the bottom for a temporary furnace, then
its harder to strip down
well glued together lams, but I chop off the copper on one side,
and use a wooden dowel and hammer to push out the bobbin and remaining
wire.
Then the lams are prized off each other one by one using a sharpened
flat blade
paint scraper which doesn't bend the lams as you remove them.

The oxide coating on the lams should stop currents flowing from lam to
lam,
but in the past to be sure I have laid out the burnt lams on a bench and
sprayed a thin coat of new varnish
on using simple clear spray can paint easy to buy.

One of my very best performing and best sounding amplifiers, the 8585
has plain non oriented silicon steel in the cores.
The distortion and saturation in this amp at all frequencies is
extaordinarily god,
and not meaningfully worse then using best grade GOSS which is twice the
price of the
non oriented core material.

SE transformers do require careful thought. Its not too hard to read my
pages and try to take in the essentials
about the number of primary turns needed for a given load and voltage,
the number of interleaved sections, thicknesses of insulations, and air
gap setting.

When I read RDH4, and many other books on OPTs, and Pts and chokes, I
was at first utterly
bewildered with what was said, and it took some time for the message to
sink in about
designing OPTs that work properly and usually better than all the
commercially made bean counter designed crap
which was sold cheaply, and which lacked any design integrity.

After I wound a few OPTs, what worked well and what didn't work became
very obvious
after I learned to measure what I wound carefully and honestly.
If you ain't your own greatest critic, you won't get anwhere.

If an ex-builder can learn the finer points of OPT construction and
function, so can you.

Much has been said of exotic core materials, such as using 50% nickel
laminations
interleaved with GOSS and then carefully gapped, and then using pure
silver wire
coated with teflon and wound on a full moon by a virgin
well trained in the trade of layer winding.

But I have used some quite attrocious iron and transformers at times
and attained sound you will die for; the issue is how you use what you
have,
and unless you get the basic numbers right, losses, Bac max, Bdc, F
response, air gap,
no amount of focus on exotic materials will give you fine transparent
music.

Always use MORE iron than really needed. Most SE OPT for 6BQ5/EL84 are
tiny walnut sized bits of junk, maybe only good for a headphone amp.

A core with a 25 x 25 centre leg section is a strating point for SE 5
watts,
and you don't need more than 2 secs and one primary section between then
the secs.
OR one can use a 20 stack of 32mm tongue material, so Afe is still
adequate but there
is more room for winding wire in the window.
Such a tranny should have its secs split into sub-sections to allow
various impedance matchings, and also to allow the use of an EL34 in
triode SE,
which will yield about 6 watts, or slightly more than an EL84 in
pentode,
and usually truely excellent SET performance.

I built a kitchen radio with an old tape recorder OPT with a better than
usual core size and
meant for SE EL84, but used with EL34 in triode, with paralleled 12AX7
driver and 12dB global NFB.
Speaker is 1953 12" Rola Deluxe in a reflex box with dome tweeter from
1972.
The sound is fabulous.

Patrick Turner.










Cheers.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[mick]

On Sat, 24 Nov 2007 13:09:23 +0000, Patrick Turner wrote:

snip

So if you are desperate for laminations, strip old or new trannies
purchased only for the laminations.

So if you buy a mains transformer of say 20VA to 50VA rating, the cost
might be
$50, but this is cheap compared to trying to source a small quantity of
new made
laminations.


Excellent - I can find the laminations then.

I also have a source for wire (all sorts) in the UK - up to 1kg on a
single reel if necessary.

At a push I can make the bobbins.

But where do you get fiberglass insulating tape? I can't find a source
anywhere, unless I'm looking for the wrong thing. Is it the self-adhesive
scrim tape used for drywall joints?



If an ex-builder can learn the finer points of OPT construction and
function, so can you.


:-)


--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[mick]

On Sat, 24 Nov 2007 15:04:42 +0000, mick wrote:



But where do you get fiberglass insulating tape? I can't find a source
anywhere, unless I'm looking for the wrong thing. Is it the
self-adhesive scrim tape used for drywall joints?



Ahhh! This might be it... Cricket bat protection tape.
http://www.prosportuk.com/detail/1/9/163

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[Patrick Turner]

mick wrote:

On Sat, 24 Nov 2007 13:09:23 +0000, Patrick Turner wrote:

snip

So if you are desperate for laminations, strip old or new trannies
purchased only for the laminations.

So if you buy a mains transformer of say 20VA to 50VA rating, the cost
might be
$50, but this is cheap compared to trying to source a small quantity of
new made
laminations.

Excellent - I can find the laminations then.

I also have a source for wire (all sorts) in the UK - up to 1kg on a
single reel if necessary.

At a push I can make the bobbins.

But where do you get fiberglass insulating tape? I can't find a source
anywhere, unless I'm looking for the wrong thing. Is it the self-adhesive
scrim tape used for drywall joints?


If an ex-builder can learn the finer points of OPT construction and
function, so can you.


:-)

Lams for such a small pair of OPT should be no trouble if you are
prepared to
sacrifice the awful attempts by the Taiwan boyos to make power
transformers I am always reluctant to buy.

It'll suit you, but I am currently assembling a pair of 45 watt SET amps
with 2 x 845 in parallel,
and the core for huge OPTs are 51mm tongue x 72 mm stack, and 2,700 P
turms, and 5S x 4P interleaving pattern
to get a load match of 6k : 6 ohms.

There isn't anything sold on the mass market electronic hobby stores
which have cores this large,
and so I pay the $15 per kg for the GOSS and buy large amounts; 50Kg is
soon absorbed by mains and OPTs
each weighing 10kg+.

The impedance ratio I need for 50 watts from a pair of 845 is very
similar to what you'll need for
EL84 pentode OR EL34 triode, and required lekage inductance and shunt C
and response and primary
inductance is also similar. The only operating difference between what I
am making and what you want
is the power rating of the OPT; my OPT needs to carry 150mA instead of
your 50mA,
V swing is 500Vrms in mine compared to 180Vrms you want.

Now because your tranny is physically much smaller, its easier to get
leakage L and shunt C quite low and lower than in my much larger OPTs.

If you do the calculations using formulas at my website, you'll see how
all this is true.

Hence you only need S-P-S interleaving arrangements.


I routinely use about 0.5 to 0.8mm polyester in larger trannies to keep
C low
AND to give good insulation between P and S layers of wires which are at
maybe 800V dc potential difference.

In your case, you won't have more than 450V dc potential, and more like
385V if you use EL34 in triode with
Ia = 65mA, for Pda = 27 waatts, from which you could get about 7 watts
of audio power measured at the anode.

I always carefully layer wind the primaries of my large OPTs, so you get
nice flat even layer
build up so that when 0.25mm+ layers of sheet polyester (which is stiff
and non pliable)
are laid on, they bed down closely to wire layers, and will adhere well
with varnish.

In your case with an OPT for low power, and only S-P-S interleave
pattern,
the sec goes on first, wound flat and neatly with wire maybe 0.85mm dia,
an then you'll need perhaps 2,700 turns of 0.2mm wire, and unless you
have a really good
transformer winding lathe you won't manage to place a required 21
consecutive layers
of 0.2mm wire on so they are all neat flat layers.
You'll find the wires will try to pile up irregularly and so its
adequately good practice
in this simple OPT to simply wind the wire on without neat layering, and
allow the wire to
randomly find its own level of build up as you turn the bobbin and
SLOWLY
traverse the feed point of wire through your hands onto the bobbin.
Its like winding cotton onto a bobbin for a sewing machine.
The slow traversing of wire feed from side to side will distribute
capacitances,
and keep potentials low between any pair of turns, and keep the
average height of wire build up fairly level . The winding wire surface
won't be flat
after placing on 2,700 turns. So the insulation should be multiple
layers of THIN
polyester, 0.05mm is fine, and then use 5 layers wound tight.

Insulation between P and S will NOT be drywall self adhesive tape used
in plastering house walls.

The best stuff is polyester sheet, or mylar, and in your case about
0.25mm will do fine, but finding a small quantity
of mylar sheet is a pita and perhaps finding 0.05mm is easier, in the
form of
polyester oven bags used for roasting a chicken within, and available
perhaps at a supermarket.

Polyester was invented in 1949 (by Dupont maybe) and allowed a
revolution
wherever a tough stretched thin plastic insulating membrane was needed,
eg, in ESL speakers.
AND far more importantly, in capacitors, where very thin films of
polyester
easily give insulation for capacitor plates with 1,000V Vdc between
them.
Polyester is cheap, and withstands getting hot up to about 200C; not as
good as teflon,
but good enough for your use. Polypropylene is also an excellent
insulation
material and also plentifully and cheaply available from stores carrying
drawing/paper supplies. But it is, like polyethylene or polythene,
unable to take more
than 125C without melting.
So the polyester is best option.
Forget trying to use plumbers teflon tape for screwed pipe joints.
You'll never get the layer thickness right, and its messy to use and
NOTHING sticks to teflon,
so even when you varnish a tranny properly, the varnish won't stick to
the teflon.
And it don't stick much to polyester, but it it is enough.

The temptation is also to use paper strips cut from one's notebook to
the neat bobbin width.
A page is typically 0.07mm thick. So you'd need say 4 layers to get
about 0.28mm.
But the effective capacitance will become higher between P and S layers
with paper
because paper has a much "higher dielectric constant" than polyester
dielectric.
The minimal amount of capacitance is present between two metal plates
when air is the insulation material.
But air is entirely impractical in an OPT and between layers of P and S
wire which act like
metal plates. Any insulation material used between charged plates acts
to effectively increase the
capacitance, and polyester has a dielectric constant of around 2.5 and
increases the capacitance
2.5 times over the same plate distance using air. Paper can have
dielectric constant of 4+
when dry, and not also soaked with varnish, when its even higher.

The capacitance between P and S should be kept well below 2,000 pF.
In you case, there is capacitance between P winding wires themselves
which will amount to an equivalent 200pF perhaps across the winding, and
then
between P winding wires closest to the final layer of S.

The final P winding layer will not be bundle of flat layers, but will
have
an uneven surface. After winding on multiple layers of THIN polyester
with varnish between them, the following layer of secondary wire can be
coaxed into laying
fairly flat over the top, but make sure the winding height stll allows a
mm of clearance
off the core lams when inserted. Failure to stick to the rules of
getting it right means you have to start all over
again, and again, until you learn the knack and get the fukken thing
right!

Unforunately, most of what I am saying goes right over the heads of most
DIYer ppl
who barely manage to tie their shoe laces, and have no tools, no work
shop,
and no practical experience at doing anything.

However, what needs to be done to make your own OPT needs to be pointed
out to all readers,
and I can reliably say that many will attempt to wind their own OPT, and
mains PT,
and chokes, and just make a mess and finish up in a tangle of kinked
wires.

One acts to make a reality of the clear mental picture of what is
required without tanging wires,
or kinking wires as one winds them on.

Swearing at the process won't ease a problem.

I always advise ppl to wind a few chokes first, just one winding, and
then move on to transformers.

This gets them used to using an improvised lathe, feeding turn on, and
doing enough of something
to test their abilities for the more complex OPT.

The simplest lathe is a hand operated drill clamped in a vice, and with
a bolt
held in the chuck used for a lathe shaft. The bobbin is made from
cardboard and placed around a wooden mandrel,
and with ply plates to support bobbin cheeks, and held tight between
nuts and washers on the bolt shaft.
The turn speed by hand is slow, but with one hand you turn, and with the
other you feed the wire on.
If the turn speed is 1 turn per second average, 3,600 turns takes an
hour, but stops and starts
and wire tangle undos can lengthem time spent.
And mistakes, like allowing the beginning wire going into a winding to
become caught
and snapping off as you turn, and this means strating all over again.

Make sure you have control of the wire and you don't allow wires at ends
of winds to flap around
and become caught.

A good seamstress really only learns to get her act together after she's
run a sewing machine
across a finger. That really focuses the girl on what she's gotta do.

Women used to wind most of the old OPTs we used to be able to buy.
They had patience, and dexterity. Their made most tubes we take for
granted ans still do.

Now us jolly good fellows who want good clothing OR diy transformers are
extremely unlikely to ever now find any woman
capable or willing to sew anything for us, or wind anything, and YOU
have to LEARN
and its something that practice IS NEEDED for and which dramatically
improves the outcome.
I bought a sewing machine. That was MUCH cheaper than getting married.
Women who sew and wind and actually do real work are only to be found in
China
where hundreds of thousands of 'em toil night'n'day to make our lives
better
while "our women" sit around letting their arse get fat.
Sorry for the social comment, but its true.
Bricklaying and sheep shearing which IS men's work also takes practice
if you wish to
see nice straight walls of bricks built in quick time and sheep that
ain't a mass of blood after shearing.
Tranny winding also requires practised skills.

My latest attempt to make an 11 kG PT for 845 amps has 48 taps and
terminations
to allow the same tranny to be used for a large variety of tubes should
845 become
un-obtainable in future due to tube production being legislated out of
existance
by the Green House Police. I can be proud of the work I have done which
will
function perfectly for the next 100 years if cared for.
The SE OPT for 845 have also got numerous taps and sectioned windings to
allow differenht SE tubes, or PP operation.

All the so called specialist local transformer winding companies all
vomit and turn purple
when I show them what I want them to wind. They are definately NOT
professionals,
and not even tradesmen. Just process workers with a narrow range.

Trouble is, most DIYers make only one pair of lousy OPTs then quit,
because they like to think they can avoid the offerings from Hammond
Engineering and
be ahead. So they make what is crap anyway. The first model boats I made
as a child were crap,
but slowly I learnt to get much better.
Then I built buildings and motorcycles, and making things became
routine.
My first OPTs looked a mess, and were poor performers, but after the 3rd
attempt they
looked much better with better termination boards and and they performed
better than
all the crap I found in Leaks and Quads and all other cheaper brand
crap.

Patrick Turner.



--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[mick]

On Sun, 25 Nov 2007 01:38:22 +0000, Patrick Turner wrote:

snip

Lams for such a small pair of OPT should be no trouble if you are
prepared to
sacrifice the awful attempts by the Taiwan boyos to make power
transformers I am always reluctant to buy.



At the moment it is possible to get non-ROHS mains transformers at low
prices, providing you aren't too fussy about the voltages. Those look
fine, but don't have corner clamp holes on the smaller sizes, so you are
restricted to the normal U clamps. That rather messes up the idea of
using 2 to make a single double-thickness core - unless they can be
drilled? At a guess it should be possible with a clamped jig and a sharp
drill.

lots of luvverly info snipped - thanks!



Insulation between P and S will NOT be drywall self adhesive tape used
in plastering house walls.


It was just a guess... :-) The cricket bat tape looks more useful.
Perhaps for holding layers or taps in position?


The best stuff is polyester sheet, or mylar, and in your case about
0.25mm will do fine, but finding a small quantity of mylar sheet is a
pita and perhaps finding 0.05mm is easier, in the form of
polyester oven bags used for roasting a chicken within, and available
perhaps at a supermarket.


Ah! 'Tis the season for transformer winding!

even more really good stuff snipped

Failure to stick to the rules of
getting it right means you have to start all over again, and again,
until you learn the knack and get the fukken thing right!


hmmm.... yeah... :-)


Unforunately, most of what I am saying goes right over the heads of most
DIYer ppl
who barely manage to tie their shoe laces, and have no tools, no work
shop,
and no practical experience at doing anything.

However, what needs to be done to make your own OPT needs to be pointed
out to all readers,
and I can reliably say that many will attempt to wind their own OPT, and
mains PT,
and chokes, and just make a mess and finish up in a tangle of kinked
wires.

One acts to make a reality of the clear mental picture of what is
required without tanging wires,
or kinking wires as one winds them on.

Swearing at the process won't ease a problem.

I always advise ppl to wind a few chokes first, just one winding, and
then move on to transformers.

This gets them used to using an improvised lathe, feeding turn on, and
doing enough of something
to test their abilities for the more complex OPT.

The simplest lathe is a hand operated drill clamped in a vice, and with
a bolt
held in the chuck used for a lathe shaft. The bobbin is made from
cardboard and placed around a wooden mandrel, and with ply plates to
support bobbin cheeks, and held tight between nuts and washers on the
bolt shaft.

I tried this many years ago. It works! Just. It's handy to get the gear
ratio sorted first, then count turns of the wheel rather than turns on
the spindle.

snip
Many thanks again, Patrick. You've been extremely helpful. :-)

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net

[Patrick Turner]

mick wrote:

On Sun, 25 Nov 2007 01:38:22 +0000, Patrick Turner wrote:

snip

Lams for such a small pair of OPT should be no trouble if you are
prepared to
sacrifice the awful attempts by the Taiwan boyos to make power
transformers I am always reluctant to buy.


At the moment it is possible to get non-ROHS mains transformers at low
prices, providing you aren't too fussy about the voltages. Those look
fine, but don't have corner clamp holes on the smaller sizes, so you are
restricted to the normal U clamps. That rather messes up the idea of
using 2 to make a single double-thickness core - unless they can be
drilled? At a guess it should be possible with a clamped jig and a sharp
drill.

Never try to ever cut or drill E&I core material. The drilling
affects the magnetic properties slightly badly.

There should be never any need to have bolt holes in small cores,
and its best to make an aluminium U clamp from some 1.2mm Al sheet.
Not having crude iron bolts through holes in the cores for any audio F
trannies is good practice.
brass bolts are best.
The U clamp is easily made by forming a channel by bending a strip of
sheet Al
around a wood block and cutting 90 degree Vs to allow folding into a U
and allowing for two bolt lugs. A rubber pad from an old car tube under
the rubber and play block
between chassis and tranny keeps the Es closely clamped to the Is in a
gapped tranny
when all is bolted to the chassis.
When the gap is finalized, the U clamp should be a sliding fit wrapped
around the wound tranny
and clamped up tight in a vice to bend the U legs tight. The Is should
be placed into the bottom of
the U first, and E's clamped down on them with gap material in place.
The U clamp is then
tightened onto the assembled tranny by clamping the U legs in the jaws
of a vice.
The E's are then hammered gently to ensure they are tight against Is and
have not slipped open.
A flat bottom strip across the bottom of the U can be bolted on if need
be.
The tranny is then soaked in molten bees wax at no more than 100C, for
an hour, or in
polyurethane varnish for an hour and allowed to drain off.
The waxed tranny can be externally cleaned and bolted to the amp
but the varnished item needs a bake at 100C for 8 hours to make the
applied polyurethane cure and dry.
Electrical varnish is better, but costs a lot in small amounts. The
waxed tranny is OK providing it
never gets hot in the amp, and it won't if you have wound it right
according to the design principles explained at my website.


Metal working skills are necessary in tube amp construction!!!!.


lots of luvverly info snipped - thanks!


Insulation between P and S will NOT be drywall self adhesive tape used
in plastering house walls.


It was just a guess... :-) The cricket bat tape looks more useful.
Perhaps for holding layers or taps in position?

For holding ends of layers or taqps, plain clear sticky tape is OK.
You should mever wind anything that tends to unravel while
you apply a layer of insulation.
One constantly battles materials that desperately try to make life a
misery.

You will soon learn the hard way if you are aleady useless with tools in
your hands.

I have a friend who is the chess champion of all 3 local chess clubs
here in a city of 330,000.
But he took 10 minutes and much direction to back his car up my driveway
today.
When I see him with a screw driver in his hand I snatch it away or else
a huge damage bill
is likely to follow.

I don't play very good chess though.




The best stuff is polyester sheet, or mylar, and in your case about
0.25mm will do fine, but finding a small quantity of mylar sheet is a
pita and perhaps finding 0.05mm is easier, in the form of
polyester oven bags used for roasting a chicken within, and available
perhaps at a supermarket.


Ah! 'Tis the season for transformer winding!

But are you the man for such a season?!

even more really good stuff snipped

Failure to stick to the rules of
getting it right means you have to start all over again, and again,
until you learn the knack and get the fukken thing right!


hmmm.... yeah... :-)

After a few repeats and a mess, Hammond, Sowter or Lundahl OPTs start to
look just fabulous.




Unfortunately, most of what I am saying goes right over the heads of most
DIYer ppl
who barely manage to tie their shoe laces, and have no tools, no work
shop,
and no practical experience at doing anything.

However, what needs to be done to make your own OPT needs to be pointed
out to all readers,
and I can reliably say that many will attempt to wind their own OPT, and
mains PT,
and chokes, and just make a mess and finish up in a tangle of kinked
wires.

One acts to make a reality of the clear mental picture of what is
required without tanging wires,
or kinking wires as one winds them on.

Swearing at the process won't ease a problem.

I always advise ppl to wind a few chokes first, just one winding, and
then move on to transformers.

This gets them used to using an improvised lathe, feeding turn on, and
doing enough of something
to test their abilities for the more complex OPT.

The simplest lathe is a hand operated drill clamped in a vice, and with
a bolt
held in the chuck used for a lathe shaft. The bobbin is made from
cardboard and placed around a wooden mandrel, and with ply plates to
support bobbin cheeks, and held tight between nuts and washers on the
bolt shaft.

I tried this many years ago. It works! Just. It's handy to get the gear
ratio sorted first, then count turns of the wheel rather than turns on
the spindle.

The old hand drill my father bought in 1959 has two ratios, about 1:3
and 1:1.

So if it isn't 1:1, you need to count the gear teeth and check 3 times
you are right.
Ths gives the actual ratio.

And then hope the phone doesn't ring in the middle of some winding
with Kylie Minogue wanting you to go around to her place for some
quality time.

So you must have pencil and paper ready to write down what you are up
to.
Its very very easy to get confused about turns and place an extra layer
in, or leave a layer out,
or have too manny or too few primary turns.
Such a tranny is as useful as a dead parrot.

And for including CFB, the P of the small tranny must be divided say
1:9,
and have a 0.25 insulation between the two sections because of the vdc
present.

You must know before you start how many P turns you think will be in
each section.

There is NO escape from having to spend a day or 3 working out the
design from
my website or someone else's. I refuse to do all design the work for
you, and have deliberately
left out important information.
I will only willingly help those who help themselves by learning,
reading, and doing a lot for themselves.

If they show they have some real passion and verve, I will check their
designs but only if
their design attempts are properly presented. This means they should be
PC savvy enough to use
MS Paint to draw a section with all sizes and turns shown and with a
summary of
wind height calculations allowing for winding lumpiness clearance et
all.
So one has to get used to scientific documentation of the experiments
one conducts.
I fill an exercise book each fortnight. I remove valuable pages with
test results and schematics,
and they form a pile I don't throw away. Do things so you would
understand what you have done in 5 years time.

There is enough information and formulas at my site to work out the
leakage inductance, shunt capacitances,
HF cut off with proposed tube Ra and RL, and LF cut off due to
saturation of primary inductance.
The checks are daunting to the unititiated to those who don't quite
understand volts, amps,
or basic laws governing R, L, or C behaviours which so commonly defy
what is normal human common sense
that hardly anyone really undertstands anything these days.
A clear understanding of equivalent circuits of tube output stages in
terms of the Ra, RL and L&C elements
is also a must to appreciate good designs.
There are at least a dozen things all interacting in a typical tube
output stage.



snip
Many thanks again, Patrick. You've been extremely helpful. :-)

And a damned challenge I would suppose..... :-)

Patrick Turner.

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net