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Here's some messages from the archive about Jeffersons.
Original poster: "Garry Freemyer by way of Terry Fritz <twftesla-at-qwest-dot-net>" <garry-at-ndfc-dot-com>
Here are some messages I saw that explain my post about Jeffersons. There
aren't as many negative messages about Jefferson's as I thought but just
finding them at least assured me a little that I am not *Completely* losing
my mind. I was beginning to think I was losing it when it seemed *I* was
just about the only one aside from Terry that remembered hearing anything
negative. I found a lot of positive posts from people that had no problem
depotting them at all. A lot more than those who had bad experiences. I do
remember the message that said they were insulated with tarpaper and the
Maybe it depends on when it was made. Perhaps they put out a few lemons and
a lot of good ones. Its much the same for hard drives. A lot of brands have
had both bad and good batches.
I think my problem was I soaked it far too long and perhaps heated it too
much trying to get the tar out. I suppose I could try to rewind the
secondary that went south but I doubt I could succeed.
Here are the messages.
Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
In a message dated 12/28/00 6:26:15 PM Eastern Standard Time,
> Also, what is the correct temp for melting tar out of a tranny in an oven
> without having the tar smoke a lot? I seem to remember 200 degrees, but
> tar wasn't even soft with this temperature after 45 minutes.
Another thing to consider about the Jefferson units, is some of them
use a silica filled tar. It's about 85% silica, so it's harder to really
melt it compared with pure tar which is more runny.
From: Bill Lemieux <gomez-at-netherworld-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Temperature to melt NST tar (fwd)
Tesla List wrote:
> For what it's worth; I haven't seen it mentioned on the list, but
> some neon trannies use tar that is filled with a silica material
> according to an insert that came with a new Jefferson tranny.
The silica material (I'm not sure what it is either, exactly) is there
to assist in conducting heat from the transformer proper to the case-
something which the tar alone is not very good at.
So much for Jeffersons not having silica in them.
I've thought it was strange that I seem to be the only one to be blessed
with such a "problem". I wonder if it's related to my NST being a Jefferson
Electric model, which has a different, non-removable shunt configuration
than most other makes. Can anyone else with a Jefferson Electric 15/60
share what their input current is?
NST's, which have a unique (non-removable) shunt construction, saturate
sooner and this is why I can pull so much current from it? But I digress...
Waltham, MA USA
Here we have the reason I mentioned that the shunts cannot be removed. I
thought that "non-removable" shunts meant not removable. My mistake. ;-)
>Original Poster: Megavolt121-at-aol-dot-com
>I Right now while i cut off shunts(these da#-at- Jefferson's don't have those
>"remove-a-shunts" and i need to cut them)
>and i want to avoid that.
Maybe I mis-read the phrase 'da#-at- Jeffersons' as an expression of
dissatisfaction with the brand.
I have a 12/30 Jefferson that I depotted to increase current. It also has a
baby blue case. I used a hot plate and a propane torch to melt the tar and
it took all day. I was very dissapointed to find no easily removable shunts
inside. I guess they are somehow built into the core on a Jefferson. I made
no changes, and repotted the core in the original container using the
original tar. I don't think I'll ever attempt another one, I'd rather go
down to the sign shop and shell out the money for a 15/120 cold cathode
transformer and not have to mess with it. Better yet, I think I'll track
down a pig!
Maybe I misunderstood this message to pertain to Jeffersons when he said he
woudn't ever attempt another one.
Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> If it's a Jefferson NST, they often use a silica filling material in
> the tar. It tends to not liquify for this reason. In any case 200
> degrees is not enough. It's a lot of work depotting those
> beasts. I did two of them, but I'll probably never do another one.
Here's at least one message that says that depotting these are a nightmare.
>I have 3 15/60 Jeffersons (the baby-blue painted ones) filled with the
>standard Black Tar. They are all dead from Tesla Duty, most with one side
Well, this fella lost three of them. I cannot find the original poster.
From: "Gomez ADDams" <gomez-at-netherworld-dot-com> (by way of Terry Fritz
I have seen Jefferson transformers fail left and right, and yet a friend of
mine has been running an older one for years in a small Tesla coil putting
out 14" streamers, and he's got no protection network! (it's got a
way-oversize capacitor of .1uF, however)
Original poster: "Mike Novak by way of Terry Fritz <twftesla-at-uswest-dot-net>"
If you paid a significant amount for this, I'd ask for a new one. It seems
it would've died no matter what application it was used in. I unpotted a
"Franceformer" about a year ago and it had an INCH thick sheet of mica on
each side of the xformer!!! It seems Jeffersons are not a good choice for
Tesla Coils after all... I've previously heard they were quite hearty, but I
guess not. Well, Good luck!