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Re: [TCML] DIY High Power Fillament transformer

Jim Mora wrote:
Hello All,

I just wanted to share my progress with a >60 amp 10, 12 volt filament
transformer. I had four older dedicated filament transformers for a quad
833C. The insulation was old!  This solution, I think, is much better.

I was lucky enough to receive a France 15/60 from a list member. That's
obviously 900VA, a good number. I was looking for a good primary, never mind
the HV coils. It happily arrived un-potted but still covered in tar. No
biggie, I soaked it in solvent a couple of days and got the two E cores and
the primary very clean. The primary was coated in poly and isolated from the
core I counted the turns on the primary (sorry, didn't write it down) and
went out to buy some #6awg. There is a LOT of room on an empty E core. I
considered #4. It was simple to wind a few layers to get in the >12 volt

I placed the halves together last night and fired it up. Of course it buzzed
big time. Solution: clear quick dry epoxy on the core flats. I plugged it in
and stacked a few MOT's on top and in a matter of minutes in quieted to
barely hearable. Cool.

I plan to have a 10v and a 12v output tap. I need to find an 800watt or so
load now - something like 6-8 100watt 12 volt RV bulbs or a 12V water heater
element. I'll let you know how the regulation turns out. Anyone have an idea
for a 12v load? Old headlamps would be good but not to be found around here.

Electric stove elements?

They're 1kW or more at 120V, so 100W at 12V.

You need 800W @ 12V.. that's about 0.18 ohms or so  (E^2/P = R 144/800).

AWG 20 wire is 0.01 ohm/ft, so 15-20 feet of wire.. stick it in a bucket of water so it doesn't melt.

Salt water and some pieces of pipe as electrodes?

Surplus resistors are available in that sort of size.

Or, Get yourself some nichrome wire (e.g savage a dead toaster or hairdryer).. They're typically around a kilowatt at 120V, or about 15-20 ohms. Take the nichrome and make multiple turns between two electrodes so the turns are all in parallel.

Say, #12awg is .001588 ohms/ foot. .2 ohms gives us 12v/.2=60amps so
.2/.001588= 126 feet of #12awg. I guess I could run it out to a tree and
back?? The air should keep it cool, not to mention the distribution of heat
over distance! - a possibility.

Go smaller and use a bucket of water to cool it.

Jim Mora

This transformer would NOT be a good solution if the filament will be
floating high above ground!

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