Patrick,
I have in the past dried out transformers by using the windings as
resistance heaters, and essentially heating the transformer from the inside
out. On something like yours, depending on the winding resistance, and turns
ratio you could simply hook up the whole inner winding to a adjustable AC
source, and crank up the voltage until you have about 50 VA of power, and
let it set to see how much it heats up. You will need to short out the other
winding so that the excited winding will in effect be shorted out. Both
windings will flow current based on the turns ratio. In cases where the
transformer has really tight coupling, low leakage inductance, and low
winding resistance, this doesn't work well because the variac will be
putting out full rated current at only a few volts ac applied. In cases like
this you need to match the impedance from the variac to the transformer to
be heated. Something like a 4-1000 filament transformer (7.5 volts 21amps)
may do the trick. Just hook the variac to the filament primary, filament
secondary to the primary of transformer to be heated, and short out
secondary of transformer to be heated. Use a AC ammeter, or clamp on Amprobe
to look at the currents to see what is going on, and to insure that nothing
is flowing too much current. For a transformer as big as yours, I would
guess that 50-100 VA should warm it up to about 45 degrees C. above ambient,
and maybe 2 hours to get there.
I am sure others in the group will have different approaches. One other
method is to bring it in the house and put it in a spot that is near a HVAC
outlet. It should be in good shape by spring!
Good Luck,
Jim
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of patrick jankowiak
Sent: Friday, November 21, 2003 9:43 PM
To: [email protected]
Subject: [AMRadio] Modulation transformer ID and repair
Hello All,
Here I have gotten the modulation transformer for the Tucker KW out,
and have had a look at it.
It seems to have windings separated by thick layers of some kind of
black (tar? -but not soft) impregnated paper. The outside has what
seems to be windings of cloth tape around it. In one place on the
bottom, the insulation has been damaged or torn enough to expose one
lead-in wire, which seems to be intact.
I have no problem dealing with this, and insulating the area, patching
up the outer covering, but here's my question:
How to hi-pot?, Any dangers in such a test?
Should I try to drive any moisture out of the transformer? It has been
in a household garage for 8 years.
Any advice what to do to take care of this part would be greatly
appreciated. I doubt I would find another one so large.
It was mounted with the frame ungrounded on a wood board. Should I
re-mount it ungrounded like that?
And yes it is extremely heavy!
Can anyone identify it? No numbers/markings except the frame says
"BETHLEHEM", and the terminals are simply marked P, B+, etc..
Here are pictures;
http://208.190.133.201/tuckerkw/modxfrtkw.html
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