Does anyone here wind their own transformers?

[daydreamer]

I'm looking for specific, practical info on this, everything I come across tends to be hi-fi related, or a bit vague. Does Merlin's book go into depth on the actual step by step winding process, not just theory?
(It's all part of the business plan BTW )

thanks

Andy

[KT66]

Winding transformers is a technical undertaking that is best left to professionals with experience. It would consume too much time and resources to get up to speed, there would be a decent capital investment, and you open yourself up to liability issues. Think about it - almost every amp company big or small outsources that part.

That being said, for purely educational reasons here is a link to a much coveted book on the subject that has long been out of print :

http://www.scribd.com/doc/36828454/Audi ... ign-Manual

I also remember a few years ago seeing someone from down under offering a video course on the subject on Ebay, it was over $100 if I recall.

Your best bet I think is to find an Aussie winder that will build to your specs. If you are lucky you might find a firm with old time knowledge and experience in making trannys for tube use.

[daydreamer]

Thanks Ryan,
Definitely not going to dive into anything.
I've been pricing up imports like Hammond, but the cost is quite high, not ridiculous though They seem to be by far the single biggest spend besides the cabinet work.
there are local companies around, but we are talking $400 per tranny.

I'm really looking into retraining in EE, so it is curiosity at this stage, but later being that 'professional' would be the aim.

downloading the link now, cheers

Andy

[Phil_S]

I see questions of this nature from time to time. Here's what I make of it.

It is entirely possible to learn to wind your own. The theory isn't that dense. Anyone who can do some basic math and apply it can figure out what needs to be done in the way of design. The design work is the easy part, if you ask me.

The more difficult part is the winding of the transformer bobbin. For a power transformer, you'll need dip it in warm varnish several times along the way. This is a messy and stinky thing to do, so you either need an outdoor location or a shop with proper exhaust ventilation and the latter is your first expense: a good exhaust fan.

You'll need a winding machine and counter. They can be bought or made. The ones you buy are modestly priced, but you'll need to wind several to make it pay. Old sewing machines are used by some. The counter is essential. There is no human I know of who can reliably count more than a few turns and you really do need to count them accurately.

I have opened up a few transformers that were in need of some repair, so I've seen the insides of both power and output transformers. Once you take one apart, you'll have a better understanding of what goes into it. See if you can find an old one that is bad -- one that someone will give you for free -- and take it apart.

My most recent adventure was to rewind a SE OT secondary. This was obviously a cheap transformer, as there was no interleaving. It also made the job possible. Because I could, I pulled out 4, 8, and 16 ohm taps from the secondary. It was "only" 150 turns, so I figured I could wind it by hand, which I did. My post-test showed that I lost count along the way. The 4 ohm and 16 ohm taps tested fairly close for intended impedance ratios, but the 8 ohm was a little off, meaning I had too few or too many turns from where I pulled it out. This demonstrated to me what a fool's errand it is to attempt to hand wind even so few turns.

Laminations will cost a bit. Magnet wire is relatively cheap. Other supplies vary. High temperature polyester tape will look expensive to the first time buyer. Plastic (nylon?) bobbins are relatively inexpensive.

Most of the replies I see on this topic are generally discouraging. "Life is too short to wind your own." Maybe. It depends on what motivates you and how you like to spend your time. The point is, you'll be investing serious time and money if you want to do this right, so be prepared.

If it floats your boat, I say go for it and do let us know how it works out for you!

[daydreamer]

cheers Phil.
Motivation is the same one I apply in my day job, I break everything down to the smallest possible steps and build my systems from there, if I find that prevailing wisdom is on the money, fine, but often I find a way through that works better for me.
At this stage, it's really to understand them fully, being such a major component.
Your experience invaluable; so even just a few more/less turns made a big difference? Wow, I guess they are prettty sensitive to variables then.

Anyway, thanks, I'm packing up for the night.

Andy

[Phil_S]

Yeah, well, when the primary has about 3900 turns, and the secondary has about 150 turns, a couple more or less is something that's noticed. I did the project because I could and it didn't cost me much. A small spool of wire was about $5. I must have spent hours on the calculations, trying to understand what size wire I needed and whether it would fit in the bobbin. In the end, it was a tight fit.

I was shooting for 152 turns with taps at 107 and 76. It looks like I got the middle 8 Ohm tap at turn 104. Assuming 10K on the primary, this made the impedance ratio at the 8 Ohm tap 9544:8. The others worked out in real life to 10225: 16 and 10000:4. Maybe this helps to set in perspective what I was doing. BTW, as you probably gathered, winding some 4000 turns on the primary by hand would be out of the question. Also, the wire is very thin, like hair, and you don't want to break it.

Read about it here:
https://tubeamparchive.com/viewtopic.ph ... highlight=

[daydreamer]

Thanks Phil,

I did read that thread when it was fresh.
I find it hard to search the forum for things though, when just about every thread mentions transformers, caps, resistors and tubes, it takes a while to find the relevant ones.

thanks for the reply, that is exactly what I needed. I noticed alot of hi-fi related instructions/ calcs too, but then reading the information on wire thickness vs turns vs core thickness making the world of difference on the OT's (high and low roll off points), it does get complex quickly.

I guess to start with I want to understand why brand 'x' is what I need, vs hit and miss testing. At $100+ each new, I would rather like to know up front what I'm looking for and why. A bit like 'this car has a diesel engine with these specs. it will be good for towing, no so good for racing. Here is why diesels have lots of torque'

[KT66]

Found some interesting reading relating to transformer winding that I thought some might find interesting.....

An article on Geofex about the subject : http://www.geofex.com/article_folders/x ... former.htm

An article from a HiFi Aussie builder with pics of his DIY winding lathe - lots of interesting stuff on his site : http://www.turneraudio.com.au/output-trans-winding.htm

A list of relevant books and magazine articles : http://www.harpamps.com/micKcircuits/Tr ... -Info.html

A paper by the esteemed Alexander Bereskin about building a 50w amp including an extensive section on making the trannys : http://www.pmillett.com/file_downloads/ ... uildit.pdf

The source Bereskin listed 50 years ago for the E-I cores is still in business at the same location, but I bet they probably don't supply 1 trannys worth for a hobbyist any more : http://www.thomas-skinner.com/transform ... ations.htm

[da Geezer]

A guy from Queensland used to post over @ the Hoffman forum. He is a 2nd generation winder & seemed to know his stuff. His handle is amp_mangler

http://www.el34world.com/Forum/index.ph ... ile;u=1222

He hasn't been active since 2009, but his email may still be good.....you could at least give him a shout & see if he could help you.

amp_mangler AT yahoo.com

HTH, Geezer

[daydreamer]

cheers KT66 and da Geezer,
there seems to be a few in Oz winding their own; I'm going to have to dig a bit deeper and keep calling around, it would be extremely cool to use something wound locally.
From a cost perspective, it certainly isn't worth winding my own, especially when I see the prices Musical Power Supplies can sell for, it's hard to believe they are winding them in the USA that cheaply. I can see it would be a lot of experience and equipment needed to get that quick!

Still, just the thought of winding them makes me take note of the terminology and different methods, e.g. would I know (or care) what 'interleaving' was if I wasn't trying to work out how they are constructed ? So it's all good!!.

[tubeswell]

The best person's brains to pick on this is R.G. Keen (R.G.) who you can find over at the ampage forum. He will find lots of ways of discouraging you from winding your own.

[Cliff Schecht]

The best person's brains to pick on this is R.G. Keen (R.G.) who you can find over at the ampage forum. He will find lots of ways of discouraging you from winding your own.

RG is a regular over at DIYSB (www.diystompboxes.com). I'm sure he'd be glad to fill you in on the intricacies of transformer winding. I've wound my own SMPS transformers (and some RF stuff) but I never bother with 60 Hz magnetics, you can almost always buy what you need there. My OT collection tends to dictate my builds so unless I'm doing something new/weird, I just buy premade iron. Like others said, it's a real pain to make your own.

[daydreamer]

thanks tubeswell and Cliff, I'll give that forum a search.

I've learnt heaps, thanks guys.

Getting closer to starting first build, the picture is forming of what actually is going on in a tube amp. i guess I'm a very visual person, so once I have a clear picture of how everything interacts, i can get started.

Andy

[David Root]

daydreamer, if you still want to know how to wind transformers here is an eccentric Aussie (aren't you all?) that has done lots and details how to do it. These are hifi iron but the principles and techniques apply.

Also an excellent reference website I refer to from time to time.

www.turneraudio.com.au/output-trans-winding.htm

[Phil_S]

I might add that Patrick Turner can be found a rec.audio.tubes. He recently helped me rewind the secondary on a SE OT. It seems that you simply post your question there and if it's transformer related, eventually, he'll drop by and comment.