A Couple of Transformer Winding Q's

[Michael A]

I'm trying to design a single ended line output transformer. I'm recycling some iron from an old Jensen (the 220 speaker co, not the new T company) 70V transformer and I'm trying to fit a coil to it for a 15k:600R transformer. Anyway, I'm wondering if I should put a secondary section next to the tongue or a primary section. Anyone got the skinny?

Thanks,
Michael

 

[mikka]

CJ is the master on these issues, but I'll throw a few points in while you wait. It's nice to get your long winding close to the core, to reduce the length of wire used, and so reduce the resistance. It's nice to get your primary close to the core, to get those freqs into the iron.

I can't help you on getting level freq response, but maybe you can aim to get some primary and some secondary next to the inner core, by breaking up the winding into sections.

Now someone else can jump in and give their experience..... :green:

 

[gyraf]

Michael,

There is no simple answer.

Best option would probably be to read through the transformers meta - that one contains all the gold that we (CJ) has been able to dig up on the subject.

And be sure to track down CJ's transformer dissections - you learn quite a lot from those!!

A good place to start is maybe "RadioDesigners Handbook" - Ch.5 - "Transformers" - http://www.gyraf.dk/schematics/RadioDesigners%20Handbook%20-%20Ch.5%20-%20Transformers.pdf (3.8Mb) - that one gives a compressed view on the topic. But don't expect it to be simple.

Jakob E.

 

[CJ]

Wind the secondary first.

This will form a better bed to wind on.

If you pull a heavier wire over a thinner wire, the extra tension might cut into your pri winding.

remember, with an outie, you have hv.

you should see this v72 pre trans, they pulled the heater winding over the sec and pri, what a mess, the weakest link by far in the v72 modules.
rats nest secondary.
all bent up, bombed out and depleted, like afghanastan.

no wait, that was the 5 kv. :green:

 

[Michael A]

Thanks for the answers. I will have to refresh myself on the RDH chapter. I did a couple of searches yesterday hoping to turn up some of CJ's dissection data, but for some reason I couldn't turn any of it up.

I'm using the procedure outlined here, http://www.turneraudio.com.au/output-trans-se-calc.html

Some further info. The core I have has a 1" tongue width and a 1/2" window width. I have about a 1 1/4" stack. I am thinking, and my oh so clear yesterday notes are quite so this morning, of 5346 turns of 34 ga for the primary in 5 sections and 1080 turns of 30 ga for the secondary in 6 sections. I think this will fit, though it is a little tighter than I would want as a beginner. Does that sound about right?

I was thinking of this layer pattern 2s-5p-2s-6p-2s-5p-2s-6p-2s-5p-2s. Is that overkill? Or altogether wrong?

Thanks,
Michael

 

[CJ]

I will round up all the carnage and assemble it into one, tightly wrapped, side o beef, just like my lil sister, jus kidin.
Too much crank from TJ.

Get the 900 page Bozorth book, and Grossner, and you are set for life.

I just figured out Stairway is ripped from All Along the Watchtower.

 

[Michael A]

CJ, I found some of your dissections. Seems the A25 is much simpler than my proposed layout. Am I overcomplicating?

 

[CJ]

Try the simple way first.


Did you download OPT.exe?

 

[Michael A]

What do you think of the wire gauge choices and approximate number of turns proposed?

What is opt.exe and where is it found?

Did the bad crank wear off yet?

M

 

[Michael A]

I found the program OPT_da in the meta. Pretty cool. Are the calculations there for bobbin wound with no insulation between layers, ie only between sections?

Is old magnet wire OK to use? I have a few spools of wire that probably date from around 1960. The insulations are Heavy Formvar, Formex HF, Roevar Heavy depending on manufacturer. Never used, just old.

Who is the best source for paper to do layers and sections, or is something else better. Polyester, polypro, etc. I have a big roll of FEP around somewhere, but I can't lay my hands on it at the moment. I think it might be too thick for layers, but might be good for sections.

I think I have my winder figured out. Some assembly still required though.

Also, where can you buy small quantities of MagMetals lams?

Thanks,
Michael