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Re: de-tarring question.....
At 09:31 PM 2/12/2000 -0700, you wrote:
>Original Poster: weaver77-at-home-dot-com
>
>Probably the easest way to remove the tar is melt it in the kitchen oven.+AKA-
>It will melt at about 200 degrees F unless it is very old and dryed out then
>it may melt about 250 or 300 degrees at the most.
>
>Try the lowest temperature first.+AKA- As long as you don't over heat the
>tar it
>won't produce any smoke. Put aluminum foil around the case to contain any
>leaks.+AKA- Remove the cover on top of the case. After one hour in the oven at
>200 deg F check to see if the tar is melted.+AKA- If not turn the heat up
>to 250
>and wait another hour.+AKA- When the tar is liquid you can simply poor the tar
>out of the case like water.
>
>There is nothing holding the transformer inside the case so be careful not
>to let the transformer fall out.+AKA- Cut the wires off at the
>insulators.+AKA-
>Remove the transformer and wipe it with a rag.+AKA- The transformer is very
>easy
>to dissamble while its is still hot.+AKA- Remove the screws and coils.
>After it
>cools wash the pieces with gasoline to remove all the tar.
>
>Now it is ready to re-assemble.+AKA- Be sure to put the coils back on the same
>way they came off.+AKA- Remove a few of the shunts to increase the current
>output.+AKA- Use a ma meter to find the correct location for the coils and the
>correct number of shunts. Be sure each coil produces the same amount of
>current. Wedge the shunts and coils in place with polyethylene so they can
>not move. Put the transformer in a box filled with high voltage oil.+AKA- You
>can build a box from plywood coated with polyester resin or make one out of
>plexiglass. Be sure you have 1/2" of oil around the sides of the transformer
>and 1" of oil above the transformer. Now the thing is almost indestructible.
>
>You and also mix 50% used tar with 50% high voltage oil in a pan.+AKA- Heat it
>on a camp stove or BBQ grill outside until it melts and mixes. Put the
>transformer back into its original case and pour the liquid tar into the
>case until it is full.+AKA- This is not as good as HV oil in a box but its
>much
>better than the old dried out tar.
>
>Gary Weaver
>+AKA-
>
>Tesla List wrote:
>
> > Original Poster: peterB <zardoz-at-albany-dot-net>
> >
> > Hi,
> > I have a double spark coil that is filled with (tar?). Black and hard,
> > but waxy.
> > I would like to remove it. I know nothing about de-tarring transformers,
> > but think the
> > process would be similar.
> >
> > How is it done?
> >
> > Thanks,
> >
> > -Pete B.
>
>+AKA-
>
hi Pete I have de-potted a couple of NSTs and would like to make a few
suggestions and warnings that may be helpful to you. The kitchen oven is a
good way to melt the tar out of a transformer but there are some
disadvantages : 1 it WILL stink up your house 2 It WILL make a mess of
your oven ( Murphys Law) and you will smell tar every time you use it
until___3 your ol' lady will be absolutely furious and will NEVER let you
forget the time you "cooked" a transformer in the oven. You may have to buy
a new oven to restore domestic peace and tranquility <grin>
I fashioned a sort of dutch oven out of two throw away turkey pans
and some tin foil and used the burner on my Cajun cooker. Those little $20
table top gas grills would probably work pretty well too. Anyway I think
the key here is "keep it outside"
Once the bulk of the tar is poured off I use a "poor mans parts
washer" which is a 5 gallon bucket or other suitable container filled with
enough kerosene or mineral spirits to cover the parts and a small 12
V submersible bilge pump ( obtainable from west marine or wal-mart for
about 15 bucks) powered by a car battery or battery charger. Place the
bucket where in the unlikely event that it catches fire it won't hurt
anything and let'er rip. Come back in an hour or two and see how it looks.
This saves an awful lot of scrubbing and is useful for cleaning all kinds
of greasy things.
After going through all that trouble to clean that tar off the
coil surely you don't want to put it back do you? I have found a good
alternative to tar is household paraffin wax like you would use for home
canning.( It's about a $1.30 a Lb at your local grocery store) It seems to
have the advantages of tar and oil. If the transformer begins to overheat
the wax will melt and act like oil increasing your heat transfer. Under
normal conditions its a solid so it won't splash around or leak and its
dielectric strength is adequate if not similar to transformer oil. If you
need to de-pot the coil again just heat it up and pour it off, you won't
need the solvent wash again. And this stuff doesn't even stink! The main
disadvantage is the case will have to be sealed very well. I use epoxy on
all metal seams, replace gaskets on the bushings and use silicon sealant on
the bushings.
Hope this helps
Good Luck
Bruce Ives