diytube.com

Hi Yves,

Lams are odd... no modern analog. Similar to EI84/EI-112, but 0.8mm larger in all but centre pole.

** edit **

Got them!

Stack = 48mm thick.


Here's outer physical dimensions:



Cheers!

TNXTU !

First estimation gives about 1 Tesla if used at 30 Watts/30 Hz.

And yes, I've seen Philips designs using paralleled primaries.

Still investigating . . .

Yves.

Hi Geek, Yves, Ed, and others:

The core size for the A-470 is an EI-112 and the stack height is 1.875".
Standard holes. The grade of lamination is 29 gauge M6.

You should assign polarity dots in your schematic or identify (i.e., use an asterik) each reversed winding.

Paralleled windings would have the same number of turns... must have the same number of turns.

To gain a further understanding of this design... dig up David Hafler's patent (circa 1954)... it is dense but provides a lot of insight into the logic of the subject coil design. And you can check your work against it.

And if you are really fascinated with the design principles and precepts of audio transformers go further back and dig up Herb Keroes' and David Hafler's jointly held transformer patent (circa 1950, 1951?) and absorb the info in that text. It will provide an interesting contrast to David's later (A-470) design work. And if you had access to the A-460 design (it was never built commercially) you'd be even moreso impressed.

Then study the Williamson transformer--- which has been published (from memory audio engineering magazine circa 1948)--- it is quite different than either the Acrosound or Dynaco design approach. But, is never-the-less another successful approach in it's own right...

Then... one might want to consider the Quad output transformer design. Yet one more classic.

So many commanding examples of fine work... all of them amply illustrate that audio transformer design is both an art and a science.


best of,

MSL

Hi ,

Many thanks for informations and suggestions.

If you (or someone else) know link to the named papers, please let us know.

TIA.

Yves.

Hi,

I have a second bobbin here and can confirm there is a difference in the winding turns.

Cheers!

Welcome to, Mike of Magnequest!

I really do like the MQ-565s, but unfortuneately these are about impossible to obtain these days, I was lucky enough to score a pair of these a few years ago, as part of a larger deal.

I've been gradually riffling through the many boxes o' iron, but haven't yet located the "dud" dynaco Z565 - I hope that I didn't end up just tossing it before the move...

I wonder if Trafomatic observed any "specialized" winding techniques with their toroidal ST35 and ST70 OPTs, or are these just simple, serially tapped, solenoid type windings, without any of the interleaving and parallel winding techniques.

I don't know just how many of the Trafomatic ST35 OPTs are in the USA, I know that I and Shannon, each have a pair of them, as well as the proper toriodal power tannies, but I haven't seen or heard of too many more of them around here.

/ed B in NC

Ed, did you get to complete any of the Trafomatic builds?
I don't recollect seeing anyone else (other than myself)
build a Dynaco design with these transformers.

Prasad

I haven't yet completed any of the Trafomatic builds - the move from New Hampshire to North Carolina pertty well put any major projects on "long term holding pattern".

I did wire up the ST35 Trafomatics to one of the DIY35 boards, for a test, and it worked and sounded pretty good. The power trannie delivers a somewhat higher than standard ST35 B+ voltage, but this sin't a major problem, the PSU first resistor or choke could be increased in resistance value, or just reduce the EL34 bias to30 mA from 35 cathode current, in order to not exceed the maximum safe plate dissipation.

For the "Herniator" ST70, I actually went in the reverse direction, and undid the original mechanical assembly, I had to remove the three rather heavy toroidal trannies, from the chassis plate, in order to repair a minor shipping damage, and to enlarge the holes for the transformers' leads, as there was some possible wire-pinching problems. Right now, it is residing in three separate boxes, plus the plate is sitting on my workbench.

/ed B

Look forward to your listening impressions, compared to
Dynaco A-470s, whenever the "herniator" is ready.
Unfortunately, I have no way to compare them, as
I know of no one who has a ST-70 here.

I found the "unbalanced" Z565. it has the plastic insulated leads, so it is probably of Japanese manufacture, but should have the same winding techniques (hopefully).

If you want it for performing an "alien autopsy" I can send it to you. Just PM me your mailing address up there in the frozen lands of Chilly-Wack, BC , and I'll get it out to you in the next couple days. I took the liberty of removing the end bells, as you won't really be needing them.

The Z565 is unbalanced in that one side of the primary has about twice the DCR from B+ to plate, of the other side. It still worked in an ST35, but the sound wasn't just quite right...

/ed B

Speaking of end bells ... I replaced a bunch with Uncle Ned's
cool nickel plated ones, so I have some new black ones
laying around if anyone needs a set for a re-furb.

... tom

Heya Ed,

The tranny arrived today :-)

What a professional packing job!

Will have a go at 'er soon.

Cheers!

Fifteen Days! WOW! Hats off to CanPost! (It only took 10 days for a package of five glass insulators to arrive in NC, all the way from Minsk, Belarus).

But then they travelled most of the distance by air, rather than by Dog Sled team and Musk Ox Express ;-)

But then, the last 7 or 8 miles, the package were carried in the mail-maiden's tiny Toyota "half-a-car", over one of NC's more twisty and turny roads...


Well, I've never been accused of under-packing, and most times, folks probably curse me out while they are valiantly attempting to open up my packages, especially if they contain fragile items like tubes or glass insulators. I like to think of these packages as being a serious challenge to Houdini ;-)

Besides, it usually keeps the customs weenies out... "Fedrones" aren't generally up to facing such challenges. ;-)

Good luck with unwinding it and counting all of the turns, , once you get it off the laminations.

Chances are that one side has a burnt-out or otherwise internally disconnected parallel primary winding, you can pre-test for this with a quick DCR check.


/ed

Hi Ed,

I'll be on the lookout for a cooked winding.

EWBrown wrote:Fifteen Days! WOW! Hats off to CanPost! (It only took 10 days for a package of five glass insulators to arrive in NC, all the way from Minsk, Belarus).

As of late, my shipments to England have been 48 hours and even just 4 days to India!

I think CanPost and Australia share the same dead donkey - my last time to .au for a parcel: 168 days D:


Cheers!

Geek wrote:Hi Folks,

Of all the things Dynaco may have cheaped out on, the OPT wasn't one of them. It's a work of art!
Winding counts are actual and typical for handwound:
So yeah, that's what I did with my weekend
Cheers!

Hi, Geek !

Occasionally found this very old but interesting thread.
Winding schematic you posted is very similar to so called Leakey-Gilson parallel-wound and is designed to improve stability at high frequencies for UL output stages.

BTW, what was leakage inductance of that transformer? It uses 3x2 sectioning and this may result in quite high leakage inductance.