[Milsurplus] [ARC5] Old Dynamotors- Don't be a DooFuss Like Me....

[J. Forster]

Yes, but you should limit the power to a few to a few tens of watts. If
you put too much power in, you may not notice it until too late.
Transformer have a lot of thermal inertia and DC heats them from inside.

You can do this with many dynos also. Just pull the input side brushes, so
only the shunt field is powered..

-John

==============


> Another trick that works is to apply DC current to the primary in a
> sufficient amount to heat the interior via the temp rise of the windings.
>  Put several watts into it and let it sit for a day or more.  Proportion
> the current to the size of the transformer.
>
> Dennis  AE6C
>
>
> On Mon, Apr 1, 2013 at 7:09 AM, J. Forster <jfor at quikus.com> wrote:
>
>> For years, I've always baked out stuff with non-hermetic magnetics.
>>
>> I put the thing on a few bricks, put a couple of 100 Watt incandescent
>> lamps underneath it, and a big cardboard box with some holes in the top
>> over it, and let it sit for a week or more.
>>
>> You want the thing to get up to about 130F for several days, at least.
>> Longer is better, IMO.
>>
>> YMMV,
>>
>> -John
>>
>> ==============
>>
>>
>> > On Mon, Apr 1, 2013 at 12:50 AM, David Stinson <arc5 at ix.netcom.com>
>> wrote:
>> >
>> >>
>> >>
>> >> I thought about putting the whole thing sans end bells into a
>> 200-degree
>> >> oven for a couple of  hours to dry it out
>> >>
>> >
>> > This is  a problem with big chunks of iron in old transmitters, too.
>> Many
>> > do not realize how similar to a sponge the laminations and windings
>> are.
>> > And old transformer left sitting in a damp cellar or storage shed is
>> an
>> > accident waiting to happen if you just haul it out, hook it up, and
>> apply
>> > voltage. Might happen in 5 seconds, 5 hours, or 5 days, 9.9999 times
>> out
>> > of
>> > 10 it'll zorch.
>> >
>> > The oven works great as is provides a means of getting rid of the
>> moisture
>> > without introducing more. On bigger pieces it can take a day or two,
>> maybe
>> > more, to feel safe enough to put power to it. And there's never a
>> > guarantee, of course. But recovery rate is far, far better when dried
>> out
>> > than when not. The trick is to heat it up long enough for the heat to
>> > reach
>> > the core and drive out the moisture. It's all about the mass. Smaller
>> =
>> > faster; hours vs days.
>> >
>> >
>> > A good reminder as many of my dynamotors are out in the garage here in
>> > humid NC. Though lately humidity has been amazingly low.
>> >
>> > ~ Todd,  KA1KAQ/4
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