Audio trafo winding help

[mitsos]

New trafo 10K:150+150 
Same format as the last one, P-S-P-S-P, primary wound with 39AWG, secondary with 33AWG.
Thinking back I could have maybe split the secondaries further or done them bifilar, for better balance. but anyway. Shield was 40AWG wire.

Pri1 = 7 layers of 174 turns
shield
Sec1 = 5 layers 85 turns
shield
Pri 2 = 6 layers of 174
shield
sec2 = 5 layers of 85
shield
pri 3 = 7 layers of 174

total pri = 1218+ 1044  +1218  = 3480 turns
total secondary = 425+425 = 850 turns


turns ratio:
Sec in series= 4.09:1 ,
Secondaries in parallel = 8.18:1

Inductance
Pri L (couldn't get good reading, might be 63H, calculating from 600 Ohm secondary (4.45H) gives 74.45H)
LeakageL (one sec shorted = 54mH, both shorted = 16.9mH)
DCR = 540 Ohms

Capacitance across pri
140pF (sec open)
140pF (sec shorted)

(16.9mH and 140pF resonate at 103.5KHz? Is that correct?)

Looking better? I have a new 10K:10K to wire up and test as well.

Question, the only way I could get capacitance readings on this was connecting the shields to the meter common (along with the end of the winding). Otherwise I get negative readings.

 

[mitsos]

Revisiting this thread as I'm about to wind a couple more of these trafos as 10K:600. 

In an attempt to improve things, or at least experiment more, I thought of doing one with the secondaries side by side as pies and another with the secondaries wound bifilar.  Both of these methods were used in older transformers and I'm curious as to what the effects might be in use, so I want to do one of each and test side-by-side.

I have a practical question on how to best wire the secondaries in series.

The basic structure will remain PSPSP.  So let's go to trafo 1, the pie-wound or side-by-side secondaries.

Goes like this
P
S1a  S2a
P
S1b  S2b
P

All primaries in series for total 10K winding.  The secondaries would also be in series, but would they go
S1a->S1b->S2a->S2b or
S1a->S2a->S1b->S2b ??

Trafo 2 would have a similar structure, but with the secondaries wired bifilar instead of side-by-side, and then put in series.

Do you jump from one section to the next when winding in series?

thanks in advance!

 

[mitsos]

OK, I did one more of these, this time with bifilar-wound secondary.  Not sure why, but DCR is WAY higher on the primary.. Must have mixed something up... Wound it with same exact turns except, obviously the secondary was half the turns because there were 2 wires being wound together. 

Anyway here are some prelim stats:

PRI DCR:
874 Ohms  (much higher than last one)
Inductance : Pretty high, but I can't get a decent reading. between 60-80H
Leakage L: 22.9 mH  (a bit worse)
Capacitance: 76.7pF  (much better)

Secondary DCR (internally wired for 600 Ohms, the last one had 2 150 Ohm windings
56 Ohms (same as last one)
Inductance:  5.4 H
Leakage L: 1.4mH
Capacitance:  Could not get a decent reading.

I hope to get both of these trafos wired up this week to the output of an RCA BC3 channel.

 

[gyraf]

[..following from sideline..]​

 

[joaquins]

Hey mitsos, what are you using for core?

Nice stuff BTW.

JS

 

[mitsos]

Hi Joaquins,

Same lams as the picture a couple pages back,  625EI lams, square stack.  Half of them are GO lams, the other half 49% nickel.  Interleaved 1:1. The nickel lams are some samples I got, the steel ones are local Brazilian stuff, a bit thinner than M6, maybe M4.

here's the pic:

http://www.groupdiy.com/index.php?topic=47852.msg603614#msg603614

cheers!

 

[joaquins]

Thanks! nice... I'd like some ni lams, I've build a couple of tx but without ni hard to get something nice for input...

JS

 

[mitsos]

I might have some extra 625EI after this project is done.  Not sure what you are planning on building, you can make some pretty hard core line inputs with it, but it's probably too big for mic inputs.

Haha, I said I'd have these wired up for testing "this week"... that leaves me less than 24 hours. 

 

[joaquins]

Start wireing!

Would be nice! I can't remember if my suplier has 625EI on M6 to mix them.. I'll ask next week to see, I'd bought 75, 62 and 25 EI from them with nice results... I've build a couple of transformers with 62 and just tested the others but any usuable tx, didn't have the time and now even less...

Would be nice to some compressor input, maybe something from neve.

JS

 

[mitsos]

62 is probably the same as 625, or might be a metric equivalent.  Close enough for us.  Half nickel and half steel in this size is a monster line input... Anyway, got entirely too much work these days, can't complain, just things are getting behind.  But I'm sure I'll have some leftovers, so hang in there.

 

[joaquins]

Yes, you are right, 62 is metric equivalent for 625... would be great, let me know if you have some left.

JS