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Re: Unpot ++
Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
Phil, all,
The one time I tried to unpot a "half-dead" NST, it was not
a pleasant experienece for me. It's probably been some 5 to
6 years ago and I can't remember too much detail as to the
brand name or exact current rating of the transformer. I do
remember that it was a 15 kV and I believe it was also a
60 mA one. I believe I tried melting it in the inside oven first
and stunk up the small house that I was living in at the time.
The wife obviously wasn't to happy about that. It seems
like I moved it outside to the BBQ grill and when I finally
got the tar (or pitch ?) melted, I had a gooey mess and still a
halfdead NST. It seems like I then tried freezing it in
the deep freezer and when I proceeded to try to chip off
the hardened gunk, it chipped off alright but the first hunk of gunk
that exposed the secondary coil took off the first
outer layer or two of the adjacent secondary coil bobbin ;^((
I even tried soaking the entire black mess in a tray of gasoline
(outside, of course) for a day or so to dissolve the tar. It takes
a WHOLE LOT of gasoline to completely remove (well you
can't COMPLETELY remove ALL of the tar) most of the tar. After over 5
gallons of gas I pretty much had a bare core/coil
assembly but STILL a half-dead NST! At this point, I was
a tad aggrevated and placed the still half-dead thing into my
trash receptacle. By now I was starting to get access to PTs
and pole pigs so I was no longer interested in going to this
much trouble to resurrect an inherently fragile transformer
which could very well fail again within seconds of power-up!
Like I said, I'm a little fuzzy as to all of the details, as it's been
several years ago and I didn't document the progress, but I do
recall it just being a generally AWFUL experience!
I know others have had more success with this process and
probably more patience than myself ;^) but that's been my
experience. Also, I hadn't come along the Terry filter yet
at this time, either. By the time I discovered the Terry filter
via this list, I had already graduated to the "pole pig" club ;0)
and in my continuing quest for bigger sparks, I kind of never
looked back to NSTs ;^) Of course, I'm sure YMMV.
David Rieben
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, November 30, 2005 11:06 PM
Subject: Re: Unpot ++
Original poster: FIFTYGUY@xxxxxxx
In a message dated 11/29/05 2:48:30 PM Eastern Standard Time,
tesla@xxxxxxxxxx writes:
> The Jefferson does not appear to have shunts that I could remove. Is
> any one on the list familiar with the inside of a Jefferson?
Yeah. I've got a Jefferson 15/30 that was part of a 15/120 farm
I used for TC'ing 16 years ago. Seemed to survive just fine,
despite the abuse it suffered. Then I pulled it out of storage last
year to run a Jacob's ladder, and it died within the first two minutes. :(
Now one side has zero output. Despite my unpotting it, poking
around, measurement, and careful observation under power, I still
can't figure out why.
At the time, I noticed the construction you are talking about.
The shunting is part of the lamination design, and yes, would
require some sort of weld breaking followed by milling/grinding to remove.
Perhaps you could drill holes through the lamination stack?
Drilling through transformer iron is not *too* bad, if you use
sharp bits and a steady fixture.
I never did like Jefferson transformers of any type.
-Phil LaBudde