CJ

Telefunken V72 Output Transformer
« on: March 16, 2013, 05:28:53 AM »
pretty easy wind, so lei's knock out a couple of these bad boys, what say?

this thing uses a mewtric lamination, 48 EI, but this is almost the same as 625 EI.

you can therefore use either/or depending on what you have access to,

here be the winding print>
« Last Edit: March 20, 2013, 12:35:00 PM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


CJ

Re: Telefunken V72 Output Transformer
« Reply #1 on: March 16, 2013, 05:50:12 AM »
here is the original hardware and lams, there is no mu can over this guy, there is a can for the pwr xfmr and the input xfmr,

werdion core brackets, terminal plate gets mounted to the stainless steel brackets,

stainless is non magnetic so the brackets will not steal any flux,

original is paper wound, we are going to use nylon bobbins that fit the 625 EI core,

you can sand down the nylon tube to get the wire closer to the center leg of the EI lams than you can with a layered paper technique, this gets the audiophools off our back when they start talkin smack about how paper sounds better because the leakage is less due to the thinner core tube,

also,  you can get more turns per layer on a nylon bobbin as you have only the bobbin thickness as your margins, paper needs more space on the sides of the layers so that they wire does not fall off or arc to the core,

« Last Edit: March 16, 2013, 05:54:38 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Telefunken V72 Output Transformer
« Reply #2 on: March 16, 2013, 11:16:37 AM »
ok here is the bobbin layout and hookup,
« Last Edit: March 16, 2013, 11:35:18 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Telefunken V72 Output Transformer
« Reply #3 on: March 20, 2013, 04:59:09 AM »
ok we wound the first V72 output and it looks pretty good,

got scary at the end, the last layer barely had room, but the more copper the better.
if you run out of room at the end then you have to rip off the copper and start over,,

we had the #34 sec wire in two coatings, Single Beldsol and Heavy Polythermaleze,

the Single Beldsol yielded more turns per layer so we used that, plus it solders.

Polythermaleze is a pain to solder, you have to use a knife to take off the insl. which can weaken the wire, so we are happy with the Beldsol, more turns and easy to solder, there is low voltage on the secondary so we dio not need a super insl. anyway.

they might have used odd gauge wire,

we used #38 for the primary and took 200 ohms off the DCR which is good,
we used #34 for the sec and went from 11 ohms to 9 ohms which is also good,

so they might have used #39 and #35 for pri and sec,

less DCR lowers distortion and insertion loss,

those buss wires go to the 4 screens>
« Last Edit: March 20, 2013, 05:08:00 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Telefunken V72 Output Transformer
« Reply #4 on: March 20, 2013, 05:11:27 AM »
here is the freq plot,

we did two sweeps, one without screens and one with the screens grounded to the sig gen ground,

voltage starts to drop at 15 k without sceens, but builds up at 15 K with the screens,

screens drop leakage C, that is why you see a diif at the hi freqs,

rez peaks at 275 k,

cable C from OPT to next appliance will probably flatten this guy to 80 K,  :D

now we get to wind the V72 Funkehauser Input with those weird discs and stuff,  :o

« Last Edit: March 20, 2013, 05:20:21 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

flatresponse

    Bietigheim-Bissingen, Germany
  • Posts: 61
Re: Telefunken V72 Output Transformer
« Reply #5 on: March 25, 2020, 01:19:51 PM »
Hi CJ,

this thread is pretty old, so hopefully you will notice my question.

So, when I got you right, you´re using a nylon bobbin with one chamber ? That´s the case as well with the original V72/2 I have.
The rest seems obvious to me, as I have already reconstructed the no longer available T188 (the original HAUFE version).
You finally used Single Beldsol wire ?  I will have to look what is the european equivalent.
My trafo winder over here is a bit cautious with fine wire, let´s see what I find.
I have access to a very close EI48 laminat, so chances are to get a good result.

Thanks for listening
Manfred


 

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