U67 transformer winding

[Spencerleehorton]

Hi,

Wanted to try my luck again with winding a couple of U67 transformers.
I see it is a 7:1 ratio and has a feedback winding of 22:1.
So if I could get 4000 winds on a bobbin and wound the 7:1 I would have say 420 winds on PRI and 2940 on SEC.
For the feedback winding is it the PRI winds devided by 22?, if so it would be about 20 winds for the feedback winding?

Could someone verify I'm going down the right track please?

Regards

Spence.

 

[Paul-o]

Hi,

I found this information over the net.

Best,

Paul-o

 

[Spencerleehorton]

Hi,

That's perfect, so as I understand it from that, the PRI is 390 turns and the SEC is 2700 turns giving the 7:1 ratio, the feedback winding is then 2700 divided by 22 which is 125 turns. This is all on each bobbin so I should be able to work this out now.
The only thing I'm not understanding is the measurements of the wire size 0,14, 0,06 ?

Regards

Spence.

 

[Murdock]

Hmm, if it is wire size, maybe you could use this for the 0,06mm windings?


http://m.ebay.com/itm/360767597241?_mwBanner=1

or this:
http://www.sauter-shop.de/kupferlackdraht/kupferlackdraht-0060-mm.html

 

[Spencerleehorton]

Ok,

So it is mm (metric)

For my windings (total amount 4000 turns)

PRI - 486 turns
SEC - 3400 turns
FB - 154 turns


Wind SEC 1st, PRI 2nd, FB 3rd

Regards

Spence.

 

[Murdock]

I would think it is in mm. As far as I know, Neumann only used the metric system.
If I may ask, why don't you make exactly the same windings as the original?

 

[gyraf]

German inches, anyone?



..come to think of it, THAT would be a strange and slightly scary concept...

Jakob E.

 

[Murdock]

Don't know if it matters, but I read somewhere, that the feedback winding is sandwiched between the primary and the secondary.
So it would be: Wind SEC 1st, FB 2nd, PRI 3rd

Also found this post by "Lukpio":

"All windings of the transformer in the U67 are connected in series for 200ohm operation, so turns are as follows:
primary:  2x2700= 5400 turns
secondary (feedback): 2x125= 250 turns
secondary (output): 2x390= 780 turns

hence the primary to feedback has 21.6:1 ratio and the primary to output about 6.9:1 ratio."

 

[Paul-o]

Here is the winding plan.

Paul-o

 

[Spencerleehorton]

Murdock, i dont have the U and I lams, im using E and I lams and i have different bobbins.

also is that a foil screen in there as well?

 

[Spencerleehorton]

Transformer wound now, just need to test. Will post results.

 

[gyraf]

Thanks, Paul-o!

Jakob E.

 

[CJ]

wow yeah ! double thanks on that! 

 

[Murdock]

Hey spence, please keep us updated! I would really be interested in one for my p2p U67.

 

[Spencerleehorton]

I've got to get a few other things done before I can put this other U67 together, so far it does check out very well.
I could try it out in my other U67 but I don't know whether this would fit?

 

[Spencerleehorton]

Hi Guys,

taken a while but i finally have a good working transformer which has been professionally tested for frequency response, signal handling and distortion. If anyone was interested in having some done i could have them professional made for £45 each as long as it was a big enough order.
flying leads or pcb mount the same price.

regards

Spence.

 

[Murdock]

Have you compared it to an original?
Would be interested in one. I could compare it to the AMI BV12.

 

[Spencerleehorton]

Ive not made any comparisons yet, have only sent to lab for full analysis, i have hand wound one which im expecting it to sound more vintage and pro wound one.
Thats great that you would be interested in test one and making a comparison,  is there a deal to be struck here?

 

[Spencerleehorton]

I've tested the transformer yesterday an sounds amazing, much better than the sowter version, which surprises me!
Need to finish building the body to put it in, but it lovely to have a U67 which works properly now.

 

[Spencerleehorton]

I've made a body for this U67 circuit and transformer, was tricky getting the switches in there!
Doesn't look that pretty but it's all solid now.