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 Vintage Windings
Has Expanded Our Vintage
Transformer Rewinding Service

Over the last couple years we have been expanding our collection of CNC Coil Winding
Machines. We have also developed a proprietary (PAF) system for winding one off, layer
wound, bobbin-less coils. These are the types of coils found in most of the vintage high
quality small signal transformers found in professional audio and live sound gear.
(Kind of sounds like makin' buggy wheels)

Vintage Windings K-241-D Layer Wound Coil

The coil above is a Vintage Windings K-241-D wound exactly as the originals, using
all original materials. In the original production runs these coils, and most other high
quality layer wound coils, were wound on long spindles winding sometimes more than
a dozen coils at the same time. A small space was left in between each coil on the
spindle. After winding, the spindle was removed from the winding machine and taken
to a cutting station where the coils were separated by cutting through the spaces
between the coils with a fine saw. What is left is a nice tight coil that just fits the core
window. It is very difficult to wind this type of coil one off because it does not use,
and cannot be properly wound with a bobbin. The Vintage Windings Proprietary
(PAF) Winding System solves this problem and produces one off, layer wound coils
exactly like the originals. They look like, and are made exactly the same as if they
were cut from a spindle but they are one off coils! This system can be sized for any
small signal and power amp layer wound transformer.

Currently we are offering our rewinding service for a number of small signal transformers
found in professional audio. There are many makes and models of these types of
transformers. Please keep in mind that if the transformer is one that we haven't
previously reverse engineered there may be an additional fee. We are currently
restoring a George Stevens 212-AM Winding Machine. This machine was the
workhorse of the industry for decades from the 60's to the 90's. We are updating
it with a Tech Taily CNC 210S . This machine, in CNC operation, will allow us
to expand into larger more industrial coils used in radio broadcast and more in
the very near future. CP

  Our Vintage Tube Microphone
Rewinding Service for
Neumann and AKG

WE can rewind a Tiny T 14/1 !! (C-12 / 24)
(That's AWG 49-50 wire!!  Yeah Baby!!)

(photo below in Recent Rewinds)

German Microphone Transformer Rewinding Service

     Several companies are currently offering a rewind service for German Tube Microphone Transformers.
Some do a very nice rewind but most services opt for a computer controlled simulation of the original
. The reason for the simulated technique over the original approach is simple economics. There is
not enough market to justify tooling up to mold the compartmentalized bobbins that were originally used. While
the CNC winding method with non-original style bobbins may return similar sonic results, often the look is not
very original. Vintage Windings bobbins are hand casted from molds made from perfect originals. The molds
were made from out-gassed and vacuum cast high quality silicon molding material. The bobbins are cast from
out-gassed high temp casting resin formulated for it's hi dielectric and heat resistant qualities. The bobbins
will exceed the lifespan of the originals significantly. The rest of the rewind is carried out following the same
techniques that were used originally. The final rewind looks correct and performs to original specifications.
We have tried 3D printing bobbins but so far we haven't found the print resolution to be acceptable in this
application. The turn around time on the rewinds is generally about two weeks, however, the bobbins are
prepared in small lots which may affect lead times.
 Please e-mail for details. Note: A complete dissection of the BV style Neumann transformers
appears on this DVD.

Recently Completed Rewinds

A note From CP:
I'm not very good about taking pictures of projects before they are shipped.
Most customers are anxious to get their gear back in operation and taking extra
time for photographs is less than prudent ;). Sometimes I do quickly take some
pics if I need to e-mail an update or create some documentation. Below are
some recent rewinds. I included some interesting notes on some of the victims.

Altec Peerless S 217-D Before Rewind

 We finally received an Altec Peerless S-217-D with an open primary. A customer had
previously sent us one that seemed to have an open coil, however, the problem with
that transformer was corrosion on the lead wire connection points. That is the most
common problem I have found with Peerless transformers. The transformer here
did have an open primary. This is a very nicely made shielded output transformer
that was found in several vintage pieces including the Pultec EQP-1A3. The
finished unit matched specs with the original to better than 1%.

Altec Peerless S 217-D After Vintage Windings Rewind.

Altec Peerless S 217-D After Vintage Windings Rewind

 This next one was a real test of patience! This was a rewind of an AKG T 14/1. These
are the tiny output transformers used in the venerable AKG C-12 and C-24 tube mics.
The first photo shows the transformer in for repair. The second photo shows another
T14 that I had next to an engineers rule. It gives you an idea of how small these units
are and the condition that they sometimes arrive in. The third photo shows the process
of making the bobbins. I have tried to 3D print the bobbins but the resolution of the print
causes the bobbins sides to be too rough and the AWG 49-50 primary wire gets caught
on the sides. (try winding that 49-50 wire large hands) The fourth photo
shows the finished rewind.

AKG T-14/1 Tube Microphone Output Transformer Before Rewind

AKG T-14/1 Tube Microphone Output Transformer Size

Vintage Windings AKG T-14-1 In House Bobbins

Vintage Windings AKG T-14-1 Finished Rewind

 This next one is a cautionary tail of sorts. The customer sent me three apparently
McCurdy AU-300 Tube Microphone Preamp Transformers. From the outside
they all
looked identical so I quoted for reverse engineering one type of transformer.
The first two cases that I opened looked like this:

McCurdy AU-300 Output Transformer Rewind Type 1 Before Rewind

Transformer cases are like a box chocolates (except they taste bad) never know
what you will find inside. The third AU-300 transformer in the same type of case looked
like this:

McCurdy AU-300 Output Transformer Rewind Type 2  Before Rewind

As you may have guessed by now, these transformers are completely different. They
have similar specs and that is the end of the similarities. The first one uses L lams
that have been glued into two blocks which were held together with phenolic caps and
bolts. The second example utilized an Arnold Cut C-Core held together with a strap.
The coils of the two types are completely different. They use different wire sizes,
different topography of winds, different turn counts. Not only that, the coils are not
the same size, nor are the core windows. Rewinding the different style coils required
reverse engineering them separately and also required machining one proprietary
winding jig for each type. That's twice the amount of the hard part of rewinding these!!

Vintage Windings McCurdy AU-300 Output Transformer Rewind Type 1 Ready for Assembly

Vintage Windings McCurdy AU-300 Output Transformer Rewind Type 2  Ready for Assembly

Vintage Windings McCurdy AU-300 Output Transformer Finished Rewind

Next Up. This one is a BV-107 from a Neumann tube microphone. There were actually
two sent to me. Both had an open primary. The bobbins that were used on many
Neumann tube microphone transformers were quite affected by the heat produced by
the tube. If the mic was regularly hung upside down chances are the bobbin will be
the reason that the coil fails. The BV-107 looks similar the BV-8,11 however it is a
slightly smaller transformer. I regret not taking better finished photos of these rewinds.
They came out nicer than they look in the photos and the tech and owner were thrilled with
the sonic results. The first two photos show one of the coils as it came to us. The third
photo shows the finished rewinds. The bobbins used in the rewinds were produced in

Neumann BV-107 Tube Microphone Transformer 1 Before Rewind

Neumann BV-107 Tube Microphone Transformer 2 Before Rewind

Vintage Windings Neumann BV-107 Tube Microphone Transformers After Rewind

 Next up is a Pultec EQH-2 Equalizer Filter Unit that came in with some problems.
Some of the frequencies were missing and upon opening the case the problem was
obvious. The first photo shows the coil and capacitors as they were removed from
the case. Scary isn't it? The caps in this unit were melted, not from the removal
from the case, I only heat the outside of the case enough to loosen the outer wax
so the whole unit slides out of the case. These caps were melted at the factory by
a potting wax that was too hot. In this case the coil was bad as well. The coils on
Pultec equalizers do not normally fail, however, the connections to them sometimes
do fail. This unit was rebuilt with NOS Aerovox and Sangamo caps as were originally
used. The coil was rewound using NOS wire of the same type as original and the
windings were matched wind for wind. The second photo is the original coil after it
was rewound. The next two photos show the finished unit before shipment. The last
photo in this series is a Vintage Windings copy of the case and coil.

Original Pultec EQH-2 Equalizer Filter Unit

Vintage Windings Original Pultec EQH-2 Tapped Toroid Inductor Coil Rewind

Original Pultec EQH-2 Filter Unit After Complete Vintage Windings Rebuild

Original Pultec EQH-2 Filter Unit After Complete Vintage Windings Rebuild

Vintage Windings Pultec Style EQH-2 Filter Unit Case and Coil Before Assembly

 Here we have a very recent rewind. This is a GN-107 from a Neumann CVM-5 Vacuum
Tube Microphone. This one looks like it's had some "home repairs". There are a couple
of interesting notes regarding this transformer. The outer winding (primary) was wound
using a technique that is very similar to Jensen's proprietary winding as described in an
AES paper from the 80's. The winding was wound by building up angled layers from one
end of the coil to the other, carefully keeping the finished winding as flat and even as
possible. I have written in a previous paper that I haven't seen this technique before
Jensen, I stand corrected. The shield winding on this transformer is not a piece of
copper foil as one might expect. The shield is a wire winding of .0045" ,( .11 mm) AWG.
One coil had a 75 turn shield and the other had a 125 turn shield. I believe the two
coils of this transformer were wound at slightly different times by two different people.
It was not uncommon to use wire shields, especially around war times when copper was
used elsewhere.  When rewinding I try to keep the look of these transformers as original
as possible, however, some original materials are often the reason for failure. In those
cases I use more modern, longer lasting materials. For instance, I use AWG 30 silicon
covered stranded wire for the bobbin lead out wires. This is 600V wire that is much more
heat resistant than the original (I can cover the silicon wire with the type of wire wrap that
Neumann used for aesthetics but the wire no longer needs it).

Neumann GN-107 - CMV-5 Vacuum Tube Microphone Transformer Before Rewind

Vintage Windings Neumann GN-107 - CMV-5 Vacuum Tube Microphone Transformer During Rewind

Vintage Windings Neumann GN-107 - CMV-5 Vacuum Tube Microphone Transformer Finished Rewind

 The owner of this transformer was very happy with the results and sent this note:

"Hi Chris, Trafo installed and sounding great!  Only bummer is that your labeling is now
invisible :-(  I thought you'd like a photo of the finished deal. Thanks again for your excellent
work on this. Best, Leo"  Photo by Leo Gillis

Neumann CMV5 Microphone with Vintage Windings rewound transformer.


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