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Re: Unpotting transformer
From: Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Reply To: Unpotting.transformer-at-ezlink-dot-com
Sent: Thursday, November 13, 1997 12:35 PM
To: Tesla List
Subject: Re: Unpotting transformer
On Wednesday, November 12, 1997 8:23 PM chestnic
[SMTP:chestnic-at-cvn-dot-net] wrote;
> I need the procedure on unpotting or cooking the transformers
The following is a part of one of Richard Quicks messages on
the USA-tesla list several years ago. (it's a shame the USA-Tesla
list went the way of the fringers and free energy freaks).
Remove all hardware, and insulators if possible. Take a hammer
and a chisel and remove the cases by splitting them down the
corners. Break off any stubborn insulators, but try to preserve
the lead wire. You are left with a block of asphalt. Set the unit
outside when it is very cold, and let it freeze solid overnite;
or place in a freezer or deep freeze until frozen solid. The next
morning, short the high voltage lead wires with a clip lead, and
connect 110 volts across the primary. Since the cores on these
transformers are shunted, they may be shorted without harm or
blowing fuses. Let the unit cook for 15-30 minutes.
Disconnect your leads, and with the chisel and hammer, chip a
groove around the block. You want to score a groove lengthwise
that will allow the block to cleave in two. Then starting from
one end of the block, chip until you hit the core, then do the
same with the other end. Pry and chip the asphalt away from the
core until the xfrmr is free. The core may then be disassembled,
and the windings removed and examined. Kerosene and a stiff brush
will clean up the windings and core of any remaining asphalt.
The "cold-cook" method is fast, clean, and works very well. Since
the asphalt is frozen and brittle, it chips away cleanly. The
"cooking" softens up the asphalt around the core, allowing it to
release. The other ways to free the cores are long soaks in sol-
vent such as kero, diesel, or gas, (the nasty waste makes a good
driveway crack filler and roofing patch), or melting out the
asphalt with external heat from a hot plate, oven, or fire.
Solvent soaks are the best done outside in summer. Get a rect-
angular kitchen type trash can. A plywood board may be used for a
lid. Fill the container with about two gallons of solvent (enough
to submerge the xfmr completely). Prepare the transformer as
outlined previously by removing the case and hardware. Submerge
the alphalt block in the solvent for several days. Remove the
unpotted core and clean up with kero and a stiff brush. This
method works best in warm weather; when it gets cold unpotting a
core this way can take a week or more. The solvent can be reused
to unpot three to five cores before it must be replaced.
Melting out the asphalt is best done outside in summer. You will
need two matching galvinized steel pans, such as those used for
catch pans during oil changes. A turkey roasting pan with a lid
will also work. Place a hot plate on some ceramic tiles. Set the
hot plate on high and center a metal pan in the heating coil. Set
the asphalt block in the pan, then cover. It will be necessary to
turn the asphalt block several times. Depending in the wattage of
the hot plate, the temperature may also need adjusting if the
asphalt begins to boil, smoke, and char. You can use a small
charcoal fire in place of a hot plate, but I feel this method is
excessively dangerous: simply set the pans up on bricks, and
build a small charcoal fire under the pan.
There is a new type of neon potting that has emerged recently.
This new potting is a cream colored opaque polymer of some type.
It is not affected by the solvents normally used to unpot neon
cores. It is recommended that this material be removed by the
"cold-cook" method. Freezing makes the material very brittle and
it will chip away easily, the warm core will allow the polymer
to release from the windings without too much difficulty.
----------------------------------------------------------------
There has been some discussion on the list on the use of d-limonene
as a solvent for removing the pitch from transformers and it is claimed to
work quite well.
Sincerely
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Alfred A. Skrocki
Alfred.Skrocki-at-CyberNetworking-dot-com
.ooo0 0ooo.
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