VintageWindings.com
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)
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)
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 vertical
sectioning. 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.
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%.
.
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 with....er....ah... large hands) The
fourth photo
shows the finished rewind.
This next one is a cautionary tail of sorts.
The customer sent me three
apparently
identical 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:
Transformer cases are like a box chocolates
(except they taste bad)....you never know
what you will find inside. The third AU-300 transformer in the same type of case
looked
like this:
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!!
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
house.
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.
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).
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
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