Re: Melting point of NST secondaries in "hot" depotting?

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Original poster: "john by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jsturgeo-at-tampabay.rr-dot-com>

Erik, The simplest way i`ve found to depot an nst or obit is to first remove
the metal can and be carefull to not break the fine secondary wires. Next,
place the trans in your freezer for about 24 hrs., now clip the two
secondary wires together and connect the two primary wires with wire nuts to
a cord with the female plug removed. Place the trans back in the freezer and
plug in the power cord and leave for about 30 to 45 minutes. The core will
get very warm making the tar quite soft but not molten. Next, after the
required time, unplug the power cord and remove the trans. and begin tapping
on the frozen tar with a hammer. The tar, after being in the freezer is now
very brittle and will crack very easily and in most cases will freely
seperate from the core. When you begin to see the the core and coils, you
may need to use a small screw driver to GENTLY pry the chunks of tar free
from the core. Care and patience at this point is KEY for successful
depotting as you do not want to nick any of the coils. One technique i use
to get the trans. "Squeaky clean" is to place the trans on a screen of
hardware cloth resting on top of a 5 gal. pail which has a submersible pump
in the bottom. The pail contains either kerosene or diesel fuel and this is
constantly being drizzeld over the trans. The action of the solvent will
wash off any of the tar that was previously inacessible. This is basically a
homemade parts washer and there are a variety of recycling pumps available,
but must be compatible with the solvent. I use an old smallblock Chevy oil
pump connected to a small A/C gearhead motor that runs about 100 r.p.m Good
luck Erik, Best regards, John
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, July 31, 2003 10:27 PM
Subject: Melting point of NST secondaries in "hot" depotting?


 > Original poster: "Erik Graham Byng by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <ebyng-at-knox.edu>
 >
 > 'evening list:
 >
 > I've got a 12/30 NST with a dead HV terminal, which I'm hopeing to solve
by
 > depotting it, maybe a little cleanup and then repotting in
 > oil.  Manufactured in '83, the (tar?) potting is by no means soft.  I've
 > chipped a sample off of the top to see if I could actually stick the NST
in
 > the oven and pour off the tar, but its got a pour temperature of close on
 > 300F.  Would bringing the case, core and windings up to that temperature
 > affect the enamel on the secondary windings, or are the windings robust
 > enough to handle it?  I plan on bringing the temperature up slowly, but
one
 > never knows...
 > ?
 >
 > Erik Byng.
 > ---
 > [
 >
 >
 >