Bill Janssen wrote:
RapidRonnie wrote:
On Apr 26, 5:55 am, "Gary" wrote:

Power, plate, audio, chokes. Email me direct for a quote.

--


Why reuse nasty old lams when new are so cheap? You'd be better to
wind something some one wants on a production basis.


Where can I buy EI laminations for a 100 Watt transformer. I need to
re-wind a couple
of secondary windings on an existing transformer. I don't think I can
remove the existing
laminations without destroying them :-(

Bill K7NOM

De laminating a power transformer is usually pretty easy... That is,
as long as they haven't run a weld bead along the side to prevent
buzzing.

What you do if first knock out the wooden wedge that holds the
lamination stack firmly in the center of the cardboard bobbin.
Then you take a thick(not flexible), sharp, putty knife, and force
it under the tongue of the first lamination that was under the
wedge. The varnish will snap easily. Next, force it under the
top, or bottom leg of the same lamination "E", and move the putty
knife around the full circumference of the "E".

Keep the knife blade flat against the lamination to minimize any
bending. They all should peel off pretty easily.

-Chuck

Chuck Harris wrote:
Bill Janssen wrote:
RapidRonnie wrote:
On Apr 26, 5:55 am, "Gary" wrote:

Power, plate, audio, chokes. Email me direct for a quote.

--


Why reuse nasty old lams when new are so cheap? You'd be better to
wind something some one wants on a production basis.


Where can I buy EI laminations for a 100 Watt transformer. I need to
re-wind a couple
of secondary windings on an existing transformer. I don't think I can
remove the existing
laminations without destroying them :-(

Bill K7NOM

De laminating a power transformer is usually pretty easy... That is,
as long as they haven't run a weld bead along the side to prevent
buzzing.

What you do if first knock out the wooden wedge that holds the
lamination stack firmly in the center of the cardboard bobbin.
Then you take a thick(not flexible), sharp, putty knife, and force
it under the tongue of the first lamination that was under the
wedge. The varnish will snap easily. Next, force it under the
top, or bottom leg of the same lamination "E", and move the putty
knife around the full circumference of the "E".

Keep the knife blade flat against the lamination to minimize any
bending. They all should peel off pretty easily.

-Chuck
Well my transformer doesn't have a wooden wedge. It has a plastic bobbin
and the
laminations are tight in the bobbin. Also the laminations were
apparently dipped in
varnish as they were assembled. I finally managed to free two of the I
laminations
using the knife trick, but there is no room for the knife between the E
laminations.

I have another transformer that is the same size, so maybe I can make
one out of two.
I would rather start with a new core though. I want to salvage as much
of the winding
as possible but the core would have to be destroyed. Oh yes the
transformer has to fit
in the original space and the original mounting holes.
Bill K7NOM

Bill Janssen wrote:
Chuck Harris wrote:

Well my transformer doesn't have a wooden wedge. It has a plastic bobbin
and the
laminations are tight in the bobbin. Also the laminations were
apparently dipped in
varnish as they were assembled. I finally managed to free two of the I
laminations
using the knife trick, but there is no room for the knife between the E
laminations.

I cannot imagine anyone working with slimy varnished laminations. The usual
trick is to vacuum impregnate the whole tranny with varnish. They put the
tranny in a pot of varnish, and draw a vacuum. The vacuum draws out any air
between the laminations, and windings. When they release the vacuum, the
varnish is sucked in to fill the vacuous areas.

You should be able to force a sharp blade under the top most "E" lamination
on the free corner. It doesn't hurt the lamination to warp it a bit. The
varnish will be very brittle, and has little tensile strength.

-Chuck