I'm trying to figure out what I need to finish the primary winding and prepare the core for the secondary.
The enameled wire got some small nicks in the enamel on the outside windings. What's the best red insulating varnish to use to repair it?

What type of mylar should I buy?
What's the best way to connect my two split windings together?

---

I've had great success using nail polish/varnish to touch up nicked copper wire enamel. It's also good (using clear nail varnish) for coating the copper side of hand etched PC boards preventing oxidation of the tracks.
Cheers
Pete'.
Edited 2026-08-05 05:18 by Pete Locke

As Peter Locke says the varnish doesn't have to be red. You could get some varnish from a motor rewinding shop if there is one near.
I just use normal polyester varnish ( stuff for wood) on my transformers. I dip them in a tub when I have finished winding them and leave them for a day or so then let them air dry.

As for mylar tape, I have used Terylene tape on my transformers, I bought some online and it is easy to work with. I would have used fibreglass tape but I hate the stuff it makes me itch too much so I went for the next temperature grade down.

Pete

On all my inductors and transformers I dip them in a solution of liquid polystyrene, then hang out to dry for a couple of days.

Get couple liters of car spray paint thinner in a metal bucket with a lid, add pieces of expanded white polystyrene, it dissolves very easily, keep adding until the dissolve rate really slows. That's your dipping solution, dries to a hard clear coating. it will soften with heat, but your transformer should never run that hot anyway.

Mike

I used this. Available from our local Home Depot store.



The beginning of this thread in another forum is how I re-wound the COTS toroid. It is smaller than what you have.
Edited 2026-08-05 23:10 by tinyt

There's this 1in 100ft of mylar for $8.20 I Was thinking about getting. They also have thicker as well. They also carry a mylar with adhesive backing.



https://cshyde.com/item/films/mylar-polyester-pet-film/2mil-mylar-1in-100ft

adhesive:
https://cshyde.com/viewitems/ategories-tapes-with-adhesive-specialty-film-tapes/mylar-film-tape-with-adhesive

anyone use Glyptal 1201 and then bake the transformer? I have a electric oven I Can bake it in.

I used to be a motor rewinder many years ago. We always baked our motors after dipping them in varnish. The only ones we didn't dip were ones that were too big for our varnish pit then we use Hymeg red varnish and gave them plenty of coats.
You asked about Mylar tape with adhesive, I have used some but it is not good for taping the whole winding on a torroid as it is too hard to get the roll of tape through the centre of the torroid without it sticking to everything.
Mylar tape that is not sticky works fine, but for me Terylene tape was much easier to use.
Pete

Thanks Ill look into terylene tape

The advantage of Terylene tape is that it can be pulled very tight without breaking.
I wind the tape off the roll around my thumb and little finger then tie the end around the middle of the stuff I have wound onto my fingers to make a bow.
That way you just pull the piece that you began with out of the bow and tape the transformer.
Terylene tape

  Godoh said  

The advantage of Terylene tape is that it can be pulled very tight without breaking.
I wind the tape off the roll around my thumb and little finger then tie the end around the middle of the stuff I have wound onto my fingers to make a bow.
That way you just pull the piece that you began with out of the bow and tape the transformer.
Terylene tape

I couldn't find terylene tape here in the USA. I did some searching and I think its the same stuff as Dacron which I can get from this place in the usa.

https://www.baewire.com/DACRON-TAPE-3-4-X-72-YRD-HSP-p/tape1122x.75.htm

That Dacron looks fine, it says it has a rubber adhesive, so that may make taping it around the torroid harder, depends on whether it is sticky before it is heated.
It looks cheap enough though to try out.
Pete

  Godoh said  

That Dacron looks fine, it says it has a rubber adhesive, so that may make taping it around the torroid harder, depends on whether it is sticky before it is heated.
It looks cheap enough though to try out.
Pete

I'll see Croylek will ship to the USA and how much it would be. The 10% tarrif isn't an issue but I've heard they can charge like $35 brokerage fee.

Motor rewinding products USA

Have a look at the above link they have polyester tape and lots of other stuff

  Godoh said  

Motor rewinding products USA



Have a look at the above link they have polyester tape and lots of other stuff

They are based in Canada but they do have polyesterlink
Edited 2026-08-07 23:07 by kentfielddude

Whats the best way to go from 16mm^2 soild copper enamel wire to a hookup wire? Compression lug?

I use crimp lugs on my connections, on my transformers the low voltage winding is fibreglass covered flat bar, so the lugs on it are crimped and soldered as well.
Solder lugs do fine too,
Years ago I bought a hydraulic crimper on ebay, it can crimp from 10mm to 320mm so does all the big connections I want to do.
Be wary of ebay lugs though, some are very thin metal and the lugs tend to break easily.
Pete

"Flag" style solder lugs can be made from copper sheet or thin copper bar.
Curl one end of the strip around the cable and drill a hole in the other end.

Drill shanks make good formers for curling it.

If you have a scrap of copper tube / water pipe it can be cut lengthwise to make some sheet.  If you are lucky it will have the right I.D for the wire already. Flatten one end for a lug or use as a joiner to flexible wire.

For connecting solid wire to flexible wire with sheet form the sheet into a tube, poke the two ends in each end of the tube and solder. Heat shrink over.
Edited 2026-08-10 13:34 by phil99

What is this type of connector called?

That looks to be a 'Crimp Link' connector that has been cut in half.



Used for joining mains cable together, but also very good for providing a hard connection point for stranded cable.
Available in a range of sizes from any electrical wholesaler of the usual on line suspects.