Winding super reverb output transformer.

[tube65]

Hello everyone,
I want the fender super reverb output transformer winding,
but I could not find anywhere in the winding information. I wonder how the super reverb ot is winding. pri - sec or interleaving?
I need help, for winding detail.

[Phil_S]

I suspect you'll need to unwind one to get the answer. Any of the companies that offer them are not likely to share what they know as it is intellectual property they will want to protect.
Have you done this work before? Making a transformer is a challenging unless you have the equipment. There is specialized equipment you'll need to buy or make. This includes counting the turns, winding them, varnish and bake, and other things. I thought I might do this, but gave up after I saw what's required.

[tubeswell]

I recently got a Schumacher OT rewound for a 67 Super Reverb - 4 primary and 3 secondary interleavings (my winding guy told me - after having meticulously unwound it so he could wind it again meticulously). 4k2:2R 50W

[R.G.]

Phil is very, very, very correct.

I won't wind output transformers, and I (1) know how to run (and even build) a winding machine (2) know what materials are needed (3) know where to get them, (4) know and have done the processes involved. I once designed transformers and even prototyped a few of them by hand as part of my full time day job.

i fully understand the burning intellectual curiosity that wants to know HOW to do something, right down to the last trick. If your purpose is to know HOW to do it, the best possible teacher is to get an example transformer like you want to wind, and perform an autopsy, right down to the individual pieces, with calipers and micrometer, and a note book to fill up with wire gauges, interlayer insulation types, turns per layer, layers, interleaving, end margins, and the thousand other things that go into it. Knowing the number of turns per winding, even the interleaving, is not nearly enough info to make a successful OT. But if satisfying your curiosity is what you're after, go for it.

On the other hand, if you just want to make one or even a few OTs for yourself, thinking perhaps that it is cheaper that way, unless you already have free access to magnet wire in all sizes, insulating sheets in all thicknesses, laminations, varnish, winding machines, and all the rest, it would be far cheaper in terms of money AND your hours to get a job flipping hamburgers, save your pay, and buy whatever trannies you want.

It's not simple, or easy, even once you have the "design" of the transformer in hand to actually make one.

[tube65]

I recently got a Schumacher OT rewound for a 67 Super Reverb - 4 primary and 3 secondary interleavings (my winding guy told me - after having meticulously unwound it so he could wind it again meticulously). 4k2:2R 50W

Thanks for the reply this is a great tip for me.

[tubeswell]

R.G. is right of course (and that is why I go to someone who's an expert winder).

[tube65]

Phil is very, very, very correct.

I won't wind output transformers, and I (1) know how to run (and even build) a winding machine (2) know what materials are needed (3) know where to get them, (4) know and have done the processes involved. I once designed transformers and even prototyped a few of them by hand as part of my full time day job.

i fully understand the burning intellectual curiosity that wants to know HOW to do something, right down to the last trick. If your purpose is to know HOW to do it, the best possible teacher is to get an example transformer like you want to wind, and perform an autopsy, right down to the individual pieces, with calipers and micrometer, and a note book to fill up with wire gauges, interlayer insulation types, turns per layer, layers, interleaving, end margins, and the thousand other things that go into it. Knowing the number of turns per winding, even the interleaving, is not nearly enough info to make a successful OT. But if satisfying your curiosity is what you're after, go for it.

On the other hand, if you just want to make one or even a few OTs for yourself, thinking perhaps that it is cheaper that way, unless you already have free access to magnet wire in all sizes, insulating sheets in all thicknesses, laminations, varnish, winding machines, and all the rest, it would be far cheaper in terms of money AND your hours to get a job flipping hamburgers, save your pay, and buy whatever trannies you want.

It's not simple, or easy, even once you have the "design" of the transformer in hand to actually make one.

IMAG2678-01.jpeg

IMAG2713-01.jpeg

Thanks for the reply
I have a winding machine. I designed it and made it, very simple and useful. winding the power transformers and the shock transformers to use my own amplifier.
but output transformer winding is really difficult. I agree with what you said.
I have a 1967 black face pro reverb with Schumacher OT, it is very simple wind, only 1 primary and 1 secondary, but the sound is really good. I cloned it. Because I seemed very simple. Even though I had a wire gauge and dc resistance. but it did not. I measure lcr meter shumaher ot is 6 henry. my clone winding is 10 henry. When I plugged the laminations of Schumacher OT into my clone, it was like original. and i understand lamination is very important. It's not just that. it is very hard to find in my country. Anyway. I have EI125 laminations from an old audio transformer. I'm wondering if the laminations are important, then maybe I could make a super reverb OT. maybe not the same, maybe better, maybe worse. I like to learn something.
sorry my english

[R.G.]

I have a winding machine. I designed it and made it, very simple and useful. winding the power transformers and the shock transformers to use my own amplifier.
but output transformer winding is really difficult. I agree with what you said.

I do apologize if it seemed I was saying that you could not do it, or did not have any background to do this. In forums, we get people posting who have many different skill levels, including no skills at all. You clearly have more than a little information and skill.

I have a 1967 black face pro reverb with Schumacher OT, it is very simple wind, only 1 primary and 1 secondary, but the sound is really good. I cloned it. Because I seemed very simple. Even though I had a wire gauge and dc resistance. but it did not. I measure lcr meter shumaher ot is 6 henry. my clone winding is 10 henry. When I plugged the laminations of Schumacher OT into my clone, it was like original. and i understand lamination is very important.

There are several different issues that come into play in any audio transformer. The bass response depends primarily on how big the primary inductance is. Bigger primary inductance lets the transformer work at lower frequencies, in exact proportion to the primary inductance. The limit on high frequency response is the leakage inductance, magnetic field that doesn't couple primary to secondary. You can measure leakage inductance by shorting the secondary winding wires, then measuring the primary inductance with LCR meter again. It will be much smaller, hundreds or thousands of times smaller. Doing the open-circuit primary inductance test and the short-circuited-secondary test, then dividing the two numbers is a primary measurement of what the audio quality of the transformer is for high fidelity (maybe not guitar amp!) uses. In the 1950s and 1960s, the ratio of primary inductance to secondary inductance was the first thing to look for in an output transformer. Hifi OTs were commonly a few thousand to over 100,000.

Leakage inductance does something else. In a push-pull output transformer like most guitar amplifiers.There is a different leakage from each half of the primary to the secondary. This makes a "flat spot" in the output wave much like crossover distortion. Hifi people hate this, but guitar people may have come to like it.

The worst winding way for leakage inductance is to wind one section of primary, then one of secondary. Splitting primary in two and sandwiching the secondary cuts the leakage by a factor of four. Splitting the secondary into three and sandwiching two halves of the primary cuts leakage by eight. This is called "interleaving" and the leakage goes down by the square of the number of places where winding changes from primary to secondary and vice versa.

Many guitar amplifiers are simple, only one primary section and one secondary section. Some have a 2-1 interleaving. Very few have a 3-2 interleaving. It is audible and measurable on a distortion meter. But maybe guitarists like it.

The simple act of stacking laminations can change primary inductance. Exactly how tightly the E matches the I on every pair of pieces matters. This makes the tiny air gap between pieces of iron the smallest. It is also important to point each "E" lamination the opposite direction from the previous one, again to minimize the air gap.

It's not just that. it is very hard to find in my country. Anyway. I have EI96 laminations from an old audio transformer. I'm wondering if the laminations are important, then maybe I could make a super reverb OT. maybe not the same, maybe better, maybe worse. I like to learn something.

It used to be that there were many different transformer metal kinds. Today, most of them are what is called "Grain Oriented Steel" (GOS) and most laminations are about the same thickness. The thicker the lamination, the more heating happens in the transformer steel because of eddy currents. The thinner the laminations, the less heating losses. But there are not many choices in lamination thickness, especially if you have to "steal" it from a power transformer. Do the best you can to find thin laminations, but do not give up because you can't find perfect, paper thin ones. Very thin laminations are so expensive that all common transformers use only a few thicknesses. If you can, measure the thickness of the laminations in real output transformers to get an idea of what is common.

sorry my english

You have no need to apologize for your english. I congratulate you on dealing with technical matters in a foreign (to you) language. I have little bits of two other languages, but I would never try to ask technical advice in those languages. So instead - congratulations on your english. It is good enough!

There is a large number of things to learn about transformers. Feel free to ask other questions.

[pompeiisneaks]

and as usual R.G. dumps a heap load of info on us to ingest!

Wowza!

~Phil

[tube65]

It used to be that there were many different transformer metal kinds. Today, most of them are what is called "Grain Oriented Steel" (GOS) and most laminations are about the same thickness. The thicker the lamination, the more heating happens in the transformer steel because of eddy currents. The thinner the laminations, the less heating losses. But there are not many choices in lamination thickness, especially if you have to "steal" it from a power transformer. Do the best you can to find thin laminations, but do not give up because you can't find perfect, paper thin ones. Very thin laminations are so expensive that all common transformers use only a few thicknesses. If you can, measure the thickness of the laminations in real output transformers to get an idea of what is common.

My laminations M6 are thin and look very soft. I bought them old fender output from transformer. Unfortunately, the thinnest paper I ever found is 0.04mm. I do not know may not be for transformer.
Many thanks for the really useful information.
best regards

[R.G.]

The quality of magnetic softness is somewhat related to the mechanical quality of softness. Transformer laminations are always annealed to be as mechanically soft as possible, as this improves the magnetic properties at the same time. Soft is good!

The topic of papers is not complicated, but is long.
* You need a cardboard bobbin/former to wind on top of. I see that in your picture of your winding under progress.
* You need very thin paper for between layers of wire. The paper is needed mostly for mechanical reasons, to keep turns from spilling off the end of the layer as layers stack up taller. In very high voltage windings, the paper also makes a longer distance for preventing shorts. The commonest material for this is called "glassine" in english, but I don't know the name in other languages. It is translucent, almost transparent, and relatively stiff for its thinness.
* You need thicker paper between sections. Again this is mostly mechanical, but partly for voltage isolation. In both of these cases, stiffness is good. Very flexible paper does not hold up the ends of the layers very well. Thickness might be 0.16 to 0.20mm. One alternative I have used is Manilla file folder material, light tan color. Again, sorry, I do not know what this is called in your language.
* You may need some quite-thick paper, maybe 0.3 to 0.4mm thick for winding around the outside of the finished windings to protect them from scrapes and bumps, and also to cover the soldered ends of the leads.
* In commercial transformers, the temperature rating of the papers is important. Ordinary paper, cardboard, manilla file folder material, brown paper and so on are usable up to perhaps 95C to 105C internal temperature. You may be OK with this in an output transformer, but I would strongly advise you to NOT use this in a power transformer. If insulation fails in an output transformer, your amp may die. If insulation fails in a power transformer YOU may die. For power transformers, use only real transformer-rated materials. These are rated in their maximum temperature. "Class 105" is most common, and is designed to be completely reliable up to 105C. Ordinary materials may fail earlier. You may find Class 130, Class 150, Class 180 and so on. You can use these if you happen to find them, but you can use ordinary materials in an output transformer.
* You will need good mechanical strength tape. We always used fiberglass cloth tape or Kapton tape. These have good adhesive and will not slip at higher temperatures. Ordinary masking tape, electrical tape, medical tape and so on, will hold firm and may slip under even tiny temperature rises. Ideally, the tape should be rated for as high a temperature as the insulation materials. Fiberglass cloth and kapton tapes will be good to Class 130 at least, so they are fine at lower temperatures.

[tube65]

what is the influence of the varnishing and baking of the transformer? Just to protect the wires? I know that guitar pickups are not good if they stay in wax for a long time.

[R.G.]

what is the influence of the varnishing and baking of the transformer? Just to protect the wires? I know that guitar pickups are not good if they stay in wax for a long time.

It does three things. First is what you think; protect wires from abrasion from mechanical movements caused by the magnetic field, as well as holding the lamination, wires, and insulation fixed in position so they don't make as much audio noise. A more subtle benefit of not moving is that the wires stay in exactly the same positions so the careful placement you did in winding stays just as you put them.

Second, it improves heat transfer from the hottest parts inside the transformer to the outside air. Solid varnish isn't a particularly good heat conductor, but it is far, far better than any trapped air bubbles. That is why the best job of varnishing is done by submerging the transformer into varnish, the pulling a vacuum above the varnish so that trapped air expands and bubbles out of the transformer. You get a more solid fill of varnish, and better cooling.

Third, it seals the iron laminates, copper wire, and insulation against moisture in the air and prevents fungus and mold attacking the insulation.

I believe the problem with pickups in wax is that it may degrade the permanent magnets. Transformer iron doesn't have this problem.

[tube65]

I have so many questions. I wish you were the top neighbor in my apartment Thank you

[Stevem]

I was under the impression that once Fender dropped Triad OTs with the end of the tweed line that interleaved OTs where a thing of the passed?