A good source for custom transformers is to use the winding and core from a
variable transformer such as a "Variac". You can often find on ebay a used
variac with cosmetic defects, missing a knob, or some such for a good price.
All you need for a transformer is an intact winding and a VA rating that
meets or exceeds your needs.

Remove the core from the frame of the unit. Tape up(2 layers) the exposed
winding conductors so that you end up with a big iron donut with two wires
protruding from under the tape. Obtain some flexible insulated wire rated
for the secondary current you need and wrap several turns (in the same
manner as the original winding)around core. The new winding does not have
to be distributed evenly around the core, just wind it on in a single layer.
Apply 120VAC to the primary (original winding) winding and measure the
voltage on the secondary. It will be some small value that can be increased
by adding more secondary turns or decreased by removing turns. Once you
reach the proper voltage, tape up the secondary winding to hold everything
in place. It will be up to you to fabricate some mounts for the assembly to
secure it with out damaging the tape. The secondary current available is
the rated primary current times the voltage ratio.

Example: Assume the original unit was rated for 120V, 10A. If the desired
secondary voltage is 5V, then rated sec. current is 10( 120/5) = 240A. The
unit rating is 10A x 120V = 1200VA.(also 5V x 240A = 1200VA)

You may have to add a turn or two to allow for winding resistance to
maintain the desired value of secondary voltage
under full load.

Randy

"Stan Schaefer" wrote in message
om...
"John Lovallo" wrote in message
...
I was just wondering if anyone has built their own bandsaw blade welder?
These seem to be awfully expensive to buy, but don't really have much to
them.

John Lovallo

I've got several magazines with plans in them. There does seem to be
a current shortage of the 200 amp, 5 volt, war-surplus, magnetron
filament transformers that they call for, though. Price out one of
those before you decide if the commercial product is too expensive.
Silver brazing is always an option and much cheaper, you can make a
jig out of a chunk of angle iron and a couple of bulldog clips.

Stan