[Prev][Next][Index][Thread]

depotting NSTs (was Re: NST insulations)



Hi Chris,

A snip here and a snip there. Comments below your questions.

> Original Poster: "Christopher Boden" <chrisboden-at-hotmail-dot-com>
> Having never de- or Re potted an NST I have a few questions :)
> 1. Is a hot-plate suitable for cooking them? Other ideas? The
>oven is NOT an option :)

It should work. Of course, it depends on the size (BTUs, VA,
etc) of your hot plate ;o)). I would stay away from open fires
as this can result in a fire hazard (even if you place them on
a steel catch tray; due to the vapors => flashpoint.).

> 2. Can I do this without stinking up the house?

Yes, but only if you do it OUTSIDE ;o)) Doing this inside the
house is GOING to get you the *look* from your wife, spouse,
girl-friend or mother.

> 3. How do I remove the shunts?

That really depends on xformer design. Best to take it one
step at a time. I donīt remember what make my U.S. NST
was (hey, that was 16.5 years ago). Usually, they are
slipped in place and held with a wedge. It may take a little
persuasion (small(!) hammer and gently) to get these out.
Once you remove some shunts, you will need to increase
the size of this wedge to hold the rest of the shunts in
place later.

> 4. How do I identify the shunts?

They look like small metal plates, similar to the laminations
your xformer is made of. Just look for the wedges, then
you will find them.

> 5. How many can I remove without toasting the thing?

This has to be found out empirically ;o). Read up on my post to
Andy (Re: Various transformer-questions) on this.

> 6. If Vasoline is used, how do I make sure to fill all the air spaces?

Good question (which is why "I" would avoid non-liquid insulators).
You COULD melt the Vaseline, but there is no guarantee, that it
will get into all pores and it only stays liquid as long as it is
heated. Oil can creep into the spaces overnight (and over-
overnight, etc).

> 7. What are other good potting compounds? I would prefer
>something easy to work with, and not liquid.

For best insulation, you have no choice except to use xformer
oil. This will creep into all spaces, which solids or semi-solids
canīt do. Also, if you do get a flashover, the oil tends to wash
it away and if you are lucky, it will *remove* all the carbon and
you are set to go again (although you may need an oil change,
then).

> 8 Is it better to keep it in it's original case, or would somehting
>like a 5Gal bucket be better?

Well, I like the original case. Itīs probably not oil tight, tho. If
you want to (and donīt have to lug it around constantly), weld
yourself (or let it be done) a large oil tight container and place
several NSTs in it (parallel them under oil). Makes for ease at
setup time. Placing it on castors allows you to roll it around.

> 9. Can wooden forms be used to place and center the
>core in a bucket?

I suppose so, but you will need wood that doesnīt rot in oil and
also is COMPLETELY moisture free. Any moisture in the wood
will contaminate your insulation liquid or whatever you will be
using.

More tips:

- If you melt the tar and pour it out, remember that there is
  NOTHING left to hold the actual xformer in the case (i.e.: the
  core WILL fall out) except the wiring and these are guaranteed
  to rip off if you just "flip over" the case after the tar is
liquidified.

- USE heavy LEATHER (not rubber) gloves, when handling hot
  NSTs and molten tar. Tar burns are VERY uncomfortable and
  can lead to infections.

- Before you completely depot one, try just to heat it up. Once the
  tar is molten, slosh it around (carefully) and let the tar re-harden.
  Test the NST. More often than not, all you have is a carbon track,
  which shorts out the NST. Doing the above, removes this trace
  and your xformer is set for more TCT (Tesla Coil Torture ;oO)).

Coiler greets from Germany,
Reinhard