Rewinding transformers.

[dragonbat13]

Just for the sake of learning, does anybody know any good links for transformer construction and rewinding?

Seems like something I would like to fool around with.

I have a lot of transformers laying around that would be good candidates.

[bepone]

it is 3 times more job than wound from 0..

the worst thing is to remove the outer varnish and to get first lamination out.. means bakng, fast handling burning transformer outside and trying to remove some laminations, failing, heating again and so on.. after some hours maybe the laminations are out.. then is to handle the bobbin, repairs..unwinding. more hours.

then are materials, insulating high voltage paper.. then hi temp tape..all need to be ready for use.

then is just basic formula for transformers,

https://www.electronics-tutorials.ws/tr ... (%20NS%20).

[neskor]

also very useful tool, transformer calculator
https://docs.google.com/spreadsheets/d/ ... ue&sd=true

[Phil_S]

This is the archive of the legacy left by Patrick Turner (RIP) who was a guru of transformer winding. He focused on commonly used tubes.
https://www.turneraudio.com.au/output-t ... alc-1.html

If you want to unwind a transformer, it is not as challenging as described. It is possible to do this without heat. Use a razor blade knife to cut the varnish on each lam, one at a time. It takes a great deal of patience. After slicing through the exterior varnish, you'll need to get between the lams, using the razor knife somewhat like a sharp spatula to gently cut/pry until it is split from the stack. A heat gun or hair dryer may be useful in softening the varnish, making it easier to split the lams. Remember to stack them on the screws in order in case you intend to reassemble. Be careful not to bend them. It could take you all day to do just one. Your hands will get tired. As a practical matter, it is probably better to limit yourself to 1 hour a day until it is done.

I know this because I have done it. Everyone should split and unwind one transformer. It is it's own sort of education.

If you have thoughts of rewinding, that is a whole other can of worms best left to someone who has the right equipment. You'll need some kind of winder (possible for a very diligent person to devise a hand crank thing, but not recommended or even a motor driven winder.) Then you'll need to apply varnish and apply a vacuum so the lams are properly impregnated (did you remove the old varnish?) Then you need to bake the thing and not in your kitchen because you won't want to cook food after using for a transformer.

I don't mean to throw a wet blanket on your wanting to do this. Please make the attempt if you have the desire! I'm just telling you that it's not for the faint of heart.

[R.G.]

Phil is right. I have unwound and rewound transformers since the 1970s, and unwinding is something that everyone with the interest should do - once, for the education. Maybe do it again if you have some transformer application where there are simply no alternatives.

I did an article on tearing down a commercial transformer to get laminations and bobbin to make a new Thomas Organ Vox driver transformer. The article shows pictures of the tear-down process and goes into some detail about wire sizes and windows for the rewind. It's here: http://geofex.com/Article_Folders/Thoma ... former.pdf

The comments about the actual winding process are right. It is reasonable to hand-wind a small transformer that uses only small, easily bendable wire and especially if you do not have to use layer insulation and where it will not be used for AC mains voltages. I have used threaded rod material on a wooden carriage and a low speed battery drill to do this, as well as a coil winding machine. It's still a demanding manual task. If you make a habit of re-winding transformers and practice lot, it gets easier and you accumulate materials to make it easier, but for doing one or a few, you will spend more money and a lot of time setting up to do the winding.

If you are new to re-winding, do not make transformers that will connect to the AC mains unless you acquire the skills to do level-wound layers with interlayer insulation and know how to maintain margins for creepage and clearance spacing. An alternative is to (re-)use a two section plastic bobbin where the insulation, creepage and clearance are taken care of by the plastic bobbin itself. Even commercial manufacturers are going to this style of winding because it's cheaper and more predictable as well as less labor being involved than the old style layer wound paper bobbins.

[dragonbat13]

I appreciate the info.

It's mostly for a learning experience. I'll be pulling one apart for sure.