When I burned up the wires on my first Metal Melter, I decided to turn the transformer core into
a stick welder. But one transformer wasn't enough to actually make it weld anything.
In this project we'll be modifying 2 microwave transformers, because more transformers means
more power.
For this project I scavenged parts from a couple more microwaves. I found these for
free on my local classifieds. Not only are we using twice as many transformers here,
but twice as much power. Seriously dangerous amounts of power. These transformers are roughly
the same size and look nearly identical except for the placement of the bases. Using an angle
grinder, we can cut down the seam of one of the shallow welds holding this base plate
to the transformer. The other seam is a little trickier to get to, but once it's cut you
can see that the base plate can now be removed fairly easily. Now these next few steps are
gonna look a lot like the modification we did in the Metal Melter project. After
grinding the welds and opening the seam with a chisel, the "I" section of the transformer
can be pulled back to reveal the precious primary and secondary coils. I've found that
the primary coil can be removed by gently prying up with a chisel. It's important to
work it out of the transformer gently because the goal is to keep this in perfect condition.
You might remember there are 2 magnetic shunts that get knocked out next, and the low voltage
winding gets removed because that won't serve any purpose here. Now to extract the secondary
coil, my method of choice is to rest it loosely on the jaws of a bench vice, then use a rubber
hammer to knock down on the transformer until the coil is free. This one finished up without
any damage at all. If you don't have a bench vice, you can improvise with a couple of blocks
of wood. In either case, your secondary coils can be salvaged in near perfect condition.
After a quick cleanup of the paper and resin, our primary coil can be replaced on the transformer
with the terminals facing down. We're gonna be re-winding a new secondary, so it's
important that we have the flat side facing up. When it comes to winding coils, life will
be a lot simpler if we build a little jig. I cut this piece of scrap wood so that it's
as wide as the center piece, and just a little shorter than the top. The length is cut so
that it overhangs the edges by about 1/2 inch on either side. We can complete the form by
adding a top and bottom panel, then forming a piece of paper to fit the sides. At this point, I think
we're about ready to add some cable. I found this 50' length of wire on clearance at the
hardware store. This is 8 gauge stranded copper wire, and cost me about $17. I'm gonna
use my vice to hold the form in place, and begin winding the cable around the center
of the form as tightly as possible. We need to build this coil 6 turns high, which isn't
too difficult the first layer, but gets progressively more challenging on the second layer, and
might seem like it's near impossible on the third. When it's packed together 6 turns high
and 3 layers deep, the paper flaps can be folded over and taped together. Now this is
the tricky part. We need to unscrew the top and bottom panels to access our coil and separate
it out of the from the form while keeping it in one piece. I used some electrical tape to ensure the
coil wouldn't unravel. Okay, it's time to transplant our new secondary into the transformer. I
have the best success by using a clamp to pinch the sides in while I push the coil down
into place. Let's just double check the coil sits flush at the top, and mix up some 2 part
epoxy glue to finish up. Just like the transformer in our Metal Melter project, the entire top
area gets a liberal coating of epoxy just before sealing it back together. In order
for this to form a strong bond, the connection will need a lot of pressure holding it together
while it sets. This is where a set of clamps or a bench vice can be invaluable. While our
first transformer is setting, we can prepare the second one in the exact same way. Our
second coil is 18 turns of 8 gauge wire exactly like the first, and transplanted just like
before. Don't worry too much about which way the coil goes in. It doesn't really matter
yet. Finally, we can glue, and clamp that together and leave it to set for around 24
hours. The final result should look something like this. The connection is strong, and the
coils are extremely snug, so any vibrations will be kept to a minimum. Well there you
have it. The basic makings of an AC stick welding system, and these two electrodes will
eventually become our clamp and stinger. From this point, it really doesn't take much more
to finish the system up and turn it into a useful little hobby welder. Look for how to
do that in Part 2. Well that's it for now. If you liked this project, perhaps you'll
like some of my others. Check them out at www.thekingofrandom.com