Mo Metal

[CJ]

Ah, good point Dan!
So thats why they epoxy the heck out of those things.
Yes, move the gap 1 mil and you have a different transformer.

Man it's gonna be a bear taking apart that 2567.
Pass the torch, Mable!
Got some leakage specs comoin in, few minutes....

 

[CJ]

Ok, here are the leakage specs for the transformers. Fairly similar.
Sowter is a little higher than the rest but not by much.
These are pretty low numbers due to the fairly small number of turns used in these transformers.

The numbers are different from transformer to transformer which may account for the difference in high end characteristics. So how does all this data relate to how the transformer sounds?
I don't know yet. Give me another 20 years of doing this and I might be able to tell you. There are people who can look at all this and tell you how it will sound, with the additional aid of the winding struture data of course.
There is nothing like a good ol fashioned listening test. Maybe I can talk Tommypiper into coming over with his Neve so we can wire up an A-B-C-D switch and have a listen.

Man, I love this new image shrinker!

 

[Kev]

[quote author="CJ"]... Yes, move the gap 1 mil and you have a different transformer. [/quote]

It may be a lot less than 1mil to make a significant difference

epoxy, aluminium bits, nuts and bolts ... they all need to be just right

:thumb:

 

[CJ]

Your probably right, Kev.
Brian Sowter told me the gap in the BA6a innerstage is 50 microns.
(0.002 in.)
:?:
I use to have to gap huge pulse transformers. Put in a slice of Nomex, clamp the C core together with three strips of 3/4 inch stainless steel banding strap, haul it over to test, haul it back, cut the banding strips off, put in a new gap, strap it up, haul it back to test.....

But, hey, I was getting paid by the hour!

 

[CJ]

If you want, I can sweep the samples again with the 1.5k .01 Zobel.
Let me know.
Also, I have abot ten times the pics of all the mag and b-h stuff that is shown here.
Let me know if you want them linked.
I will just make a huge list.

Hacksaw Reynolds will be in the operating room tomorrow!
:razz:

 

[rascalseven]

I personally would love to see the sweeps with the zobel in place.

Also, should there be any adjustments on the zobel for people (like myself) who use the Sowter or the Carnhill to get performance similar to the Marinair?

Thanks so much for all your effort and for sharing with the group!!

:thumb: :thumb: :thumb: :sam:

Much peace,

JC

 

[CJ]

Thanks JC!

OK, I am going to try and finish this thing.

Here are the frequency sweeps comparing the response with the 1.5k-0.012 (all i had) cap between the four different models.

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_comp.jpg

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/lo1166_comp.jpg

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/carnhill_comp.jpg

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/sowter_comp.jpg

Here are all four graphed on the same sheet.
Four with and four without the network.
The Sowter looks like it is doing what it is supposed to do with the network.
I can see why people say it sounds cleaner. More iron for better low frequency response, and balanced winding structure for a bessel-like rolloff, free of any roller coaster ride.
If you go back to the leakage post, you can see that the Sowter had the leakage very closely matched which is probably the reason for the smooth rolloff with the Zobel network.
But it is a matter of taste as to which sound you want from your Neve:


http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/all_nonet.jpg

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/all_net.jpg

 

[CJ]

I took apart the Marinair LO2567 and got the winding structure.
I figured that this big chunk of M6 with the heavy wire would have a simple winding structure.
WRONG! This is by far the weirdest transformer stucture I have ever unwound.

The coils are wound on a nylon bobbin that has a one inch height for the wire, so each full layer is one inch wide.

All five sections had 0.015 dia. wire in inches.
This looks like 27 ga enamel magnet wire.

There are five seperate windings in the 2567.
From the innermost layer to the outtermost, the structure looks like this:

1/2 Secondary B-Primary A-Secondary A-Primary B-1/2 Secondary B

The finish of the outer secondary gets spliced to the finish of the inner secondary.

Primary B is the only section that is reversed wound.

Each section ended with a partial layer, that is, the outtermost layer of each of the five windings had less than a full layer of turns. The partial turns are as follows from inner coil sections to outter:

Section 1: 38 turns
Section 2: 20 turns
Section 3: 15 turns
Section 4: 25 turns
Section 5: 40 turns

So the layer by layer turns number looks like this:

Section 1: 70t-65t-65-t-38t = 238t
Section 2: 62t-70t-70t-65t-20t = 287
Section 3: 69t-65t-65t-65t-65t-65t-60t-15t = 469
Section 4: 65t-65t-70t-65t-25t = 290t
Section 5: 70t-60t-70t-40t = 240t

Sections 1 and 5 are combined to give a 478t secondary.

This was a hand wound coil. All the sections were wound back and forth.
The wire tension was very tight. In some places, the wire smashed inbetween to adjacent wires from the previous layer.

I was able to measure the length of three sections:

Section 2: 86 feet
Section 4: 101 feet
Section 5: 91 feet

The innermost secondary winding had a broken wire. Probably caused by the tight tension and a core that must have gotten hot and expanded, breaking the wire. The whole transformer was probably dipped in varnish three or four times. This is what you find on the outside of these transformers. It is not epoxy.

Each section had about a 0.0015 thick piece of clear insulation that was wrapped around twice.
There was some yellow mylar tape covering the lead breakout. Otherwise, the wire was wound right on top of each other.

The start and finish leads of each section were brought out very near to each other., probably about 1/16 inch apart.

The core consisted of 54 lams of 75EI in 0.014 thick M6.
The coil weight with varnish was 3.15 oz.

I will touch up the disection pics and post them here in a while.

 

[PRR]

> 1/2 Secondary B-Primary A-Secondary B-Primary B-1/2 Secondary B

?? Typo? How many "Secondary B" are there?

> This is by far the weirdest transformer stucture I have ever unwound.

From the above, it seems like a simple 5-section S-P-S-P-S. Primary leakage flux can hardly go anywhere except through a secondary, and resistance of the 2-section windings is balanced.

> Primary B is the only section that is reversed wound.

Balances the primary-secondary capacitance.

All this is in RDH4, which is as old as rocket surgery.

> Each section ended with a partial layer

Again: making the total resistance come out right for inner, middle, and outer windings. Each turn makes the same voltage but does not have the same resistance. Someone did his sums carefully.

Or just as likely: hand-wound, turns/layer vary, they put down the specified number of turns without trying to get full layers. With very fine wire and very many layers, you can make it come out even; if you use a lot of fishpaper between layers to reduce interwinding capacitance, you need full layers so the fishpaper fits nice. But with fairly few turns and layers, you can't force it to come out even, and with yellotape it isn't necessary to lay perfectly.

> The wire tension was very tight. the wire was wound right on top of each other.

At these low impedances: Capacitance is a non-issue, leakage inductance is a Big Deal. Smash all the flux together!

> the wire smashed inbetween to adjacent wires from the previous layer.

Often seen.

> The innermost secondary winding had a broken wire. Probably caused by the tight tension and a core that must have gotten hot and expanded

Ah, bad. That's why they should not be SO tight. Little is gained. But hard to know when it is too-tight, unless it fails factory test or you get a lot of warranty returns while it is still in production on the same winder. Too loose is bad too.

> The start and finish leads of each section were brought out very near to each other., probably about 1/16 inch apart.

This is very low voltage stuff, 24V, right? And low impedance. You could twist the pigtails together. The only reason to keep them apart is so you can get the phasing right.

 

[CJ]

Corrected the typo. Thanks PRR!
One of the secondaries is split into two sections, while the other one is all one winding. Probably to balance dcr as you pointed out.
Reverse winding maybe to get a patent?
The transformer does not get hot under normal conditions. Someone probably had a circuit failure which caused high current to heat up the iron.

 

[PRR]

> Reverse winding maybe to get a patent?

This was old news when these cores were wound. Read RDH4.

 

[CJ]

OK, hatchet time!
I will show a few pics and link to the rest so the dial up guys don't sue me.

Here is the poor unfortunate victim:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_1.jpg

Heaating up the varnish to get the frame off:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_2.jpg

Got it off:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_4.jpg

Chipping away the varnish from the glass tape wrapper:


http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_7.jpg

I heat the core up pretty good.
Taking off the first I bar:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_9.jpg

Crap! Gotta run. Rest tomorrow.

cj

 

[Learner]

Aei.... blaze that, um...I mean blow fry that sticky iiiiiiiky...... Iron Tech!

 

[Kev]

I still get a cold shiver when cj does this destructo stuff.
:shock:
:sad:

Ill never quite get used to it ....

keep up the good work cj ... :thumb:

 

[CJ]

OK, back at it!
Looked thru RDH4 a with my magnifying glass and low and behold, right there on page 217 is the same winding struture as the 2567. The reverse winding thing was a little more cryptic, just a pic of a balanced secondary on page 210 (my book at least, with a sentance or two. Interesting that Sowter is mentioned in the referance sec. Brian's Dad. Partidge too. Crowehurst, wish I had some of those old mags.

OK, here we go.

Taking out the E lam:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_11.jpg

This old varnish is a pain.
But it puts out some righteous fumes! :razz:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_14.jpg

I had to do a re-heat, as the smaller stack cools off quicker:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_16.jpg

Here goes the last of the Mohicians:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_17.jpg

I've seen the heatgun and the damage done...

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_20.jpg

Like working on a mummy. This glass tape wrapper was a pain.
Very hard to get off without breaking copper:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_21.jpg

I wrote the lead numbers on the wrapper so I could keep track after de-lamming.
Then I burned them into the top of the nylon bobbin with a soldering iron.

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_22.jpg

Of course the adhesive has to seperate from the tape.
Oh well, a little alchohol helped loosen things up.
For the coil, that is:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_23.jpg

A little mo heat helped speed things up:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_24.jpg

This is the top of the bobbin after removing most of the varnish.
This is when I discovered that I messed up by cutting the breakout wires.
The coil wires for each section actually come out of the bobbin very close to each other, then get routed along top of the bobbin to thier respective pin locations.
You can not see this unless you strip the varnish off the leads, which was very difficult.
Now I don't know which is the start, and which is the finish! :evil:
But, I do know which terminal is hot and which one is cold, from the schematic. So it's easy to guess which is which. Live and learn.

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_25.jpg

Unwinding the first half-layer.
Luckily the wire is thick enough to where you can rip it right thru the iinsulation without breaking it.

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_28.jpg

Here is the next section ready to be unwound.
There was a clear piece of 0.0015 plastic insulation between each section, but nothing between each layer.
This minimizes leakage inductance.

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_29.jpg

You can really tell that this was a hand wound coil:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_30.jpg

This is how each section ended. The bobbin would get a partial fill, then the lead would angle up towards it's breakout spot on the bobbin.
You can see this on the yellow tape.
Looking from the top of the bobbin, four sections were wound in a counter-clockwise direction, with the second section reversed wound. (clockwise)

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_35.jpg

End of the line!
They wound this so tight that it left impressions in the nylon.

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_37.jpg

Here are the bobbin dimensions in inches:

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/bobbin_2.jpg

http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/bobbin_1.jpg

Here are your lam dims.:

]http://vacuumbrain.com/The_Lab/TA/Marinair/Shootout/2567_lams.jpg

Ok, that's a wrap. I mean an unwrap! :razz:

This one would be a piece O cake to DIY.

 

[gyraf]

:shock: Thanks, CJ, for another great magnetic hack..

:thumb:

Jakob E.

 

[Kev]

yep ... very good
but
it still hurts each time you do the hack
:roll:


why doesn't my camera get in nice and close like cj's can ... :sad:
... what have you got there Chris ?

 

[SonsOfThunder]

Nice job, CJ!

Thanks as always for sharing.

 

[CJ]

Kev, it's a Canon A60.
You need macro mode to get the close ups.

Weirdness, after I saturated the heck out of the new Sowter, the henries jumped from 2.4 to 3 on the secondary.
Maybe this breakin stuff ain't fiction after all.
I know a guy who tunes his SE power outputs like this.
Hit's them with 60 cps at 1 amp on the secondary until the henries match.
:?:

 

[cayocosta]

CJ,

How are you compressing those images?

Ron