Unpotting a transformer
 

I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time.
But the whole transformer is potted in some sort of black tar. I scraped
some of it out, looks like it softens at 200F, goes semi liquid at 250F,
and fully liquid at 275F. Easy enough to rig a tent over a catch basin
and aim a heater in there but what about the temp rise on the wires? I
would need to run it at the 250F to 275F (120C to 135C) range for
perhaps an hour to get all the goo out.

Unpotting a transformer
 

On Apr 21, 8:51 am, RoyJ wrote:
I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time.
But the whole transformer is potted in some sort of black tar. I scraped
some of it out, looks like it softens at 200F, goes semi liquid at 250F,
and fully liquid at 275F. Easy enough to rig a tent over a catch basin
and aim a heater in there but what about the temp rise on the wires? I
would need to run it at the 250F to 275F (120C to 135C) range for
perhaps an hour to get all the goo out.

If it survived the temperature while being potted, it should do the
same in the reverse direction......give it a go, see what
happens..........or, manually chip out enough of the gunk to get to
the secondary transformer leads and hook to them...
Andrew VK3BFA.

Unpotting a transformer
 

That's what I thought at first but when you pour the goop in, the
temperature drops rapidly, the core never sees the high temp. When you
reverse it, the leads would see the overtemp. I can get at all the
leads, I could just saw the case apart and leave it potted.

wrote:
On Apr 21, 8:51 am, RoyJ wrote:
I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time.
But the whole transformer is potted in some sort of black tar. I scraped
some of it out, looks like it softens at 200F, goes semi liquid at 250F,
and fully liquid at 275F. Easy enough to rig a tent over a catch basin
and aim a heater in there but what about the temp rise on the wires? I
would need to run it at the 250F to 275F (120C to 135C) range for
perhaps an hour to get all the goo out.

If it survived the temperature while being potted, it should do the
same in the reverse direction......give it a go, see what
happens..........or, manually chip out enough of the gunk to get to
the secondary transformer leads and hook to them...
Andrew VK3BFA.

Unpotting a transformer
 

Freeze it with liquid nitrogen and break the goop off (proper PPE of
course). I hear they use that technique to separate rubber from metal in
shredded tires.


RoyJ wrote:

That's what I thought at first but when you pour the goop in, the
temperature drops rapidly, the core never sees the high temp. When you
reverse it, the leads would see the overtemp. I can get at all the
leads, I could just saw the case apart and leave it potted.

wrote:
On Apr 21, 8:51 am, RoyJ wrote:
I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time.
But the whole transformer is potted in some sort of black tar. I scraped
some of it out, looks like it softens at 200F, goes semi liquid at 250F,
and fully liquid at 275F. Easy enough to rig a tent over a catch basin
and aim a heater in there but what about the temp rise on the wires? I
would need to run it at the 250F to 275F (120C to 135C) range for
perhaps an hour to get all the goo out.

If it survived the temperature while being potted, it should do the
same in the reverse direction......give it a go, see what
happens..........or, manually chip out enough of the gunk to get to
the secondary transformer leads and hook to them...
Andrew VK3BFA.

Unpotting a transformer
 

RoyJ wrote:

I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time.
But the whole transformer is potted in some sort of black tar. I scraped
some of it out, looks like it softens at 200F, goes semi liquid at 250F,
and fully liquid at 275F. Easy enough to rig a tent over a catch basin
and aim a heater in there but what about the temp rise on the wires? I
would need to run it at the 250F to 275F (120C to 135C) range for
perhaps an hour to get all the goo out.


http://www.minute-man.com/acatalog/E...gnet_Wire.html

Indicates a max working temp of 130C

http://en.wikipedia.org/wiki/Magnet_wire

Has a higher temp.


http://www.mwswire.com/awgsearch2.asp

Size 30 insulation PE (plain enamel)


INSULATION INFORMATION:
Temperature Class: 105° C
Insulation Type: Plain Enamel
MWS Code: PE NEMA Specification: MW 1C
Federal Specification: JW1177/1
IEC Specification: NONE
Insulation Characteristics:
Available in 40 - 44 AWG, Plain enamel magnet wire is insulation with a film of
conventional oleoresinous enamel. Enamel has good adherence, flexibility, thermal and
solvent resistance. Enamel requires mechanical stripping prior to soldering.
General Applications:
High production relays and coils. Avoid using in presence of synthetic solvents.



Looks like your mileage may vary on this one, Roy.

If you decide to do this, go low on temp and slow rather than a bit higher and quicker.

Wes

Unpotting a transformer
 

On Mon, 20 Apr 2009 21:55:56 -0500, RoyJ
wrote:

That's what I thought at first but when you pour the goop in, the
temperature drops rapidly, the core never sees the high temp. When you
reverse it, the leads would see the overtemp. I can get at all the
leads, I could just saw the case apart and leave it potted.


So what is your question, Roy?

The potting material sounds like Minerallac.

Unpotting a transformer
 

RoyJ fired this volley in
m:

That's what I thought at first but when you pour the goop in, the
temperature drops rapidly, the core never sees the high temp. When
you
reverse it, the leads would see the overtemp. I can get at all the
leads, I could just saw the case apart and leave it potted.



I worked for Transitron in their prototype testing lab, back in the
'70s.

Properly done: You bake the core to potting temperature to ensure a
bond, and to drive out moisture. Pour in the molten Aslac. (Gilsonite
and mineral oil-- we used to blend our own).

You pull a vacuum with the item completely immersed in the potting
compound, then release the vacuum. All the interstices are filled.


Then you cool it. The core definitely sees the whole temperature --
you bring it up before adding the potting comp.

Wire with a "working temperature" of 130C can easily take a passive
run to 150C (with no voltage across a coil).

LLoyd

Unpotting a transformer
 

On Apr 21, 7:01*am, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I worked for Transitron in their prototype testing lab, back in the
'70s. *

LLoyd

Did you know George Roach?

Unpotting a transformer
 

Jim Wilkins fired this volley in news:7eee5e00-
:

On Apr 21, 7:01*am, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I worked for Transitron in their prototype testing lab, back in the
'70s. *

LLoyd

Did you know George Roach?


Lord! That name is awfully familiar... but it's been a lot of years
since then... I just don't remember.

How 'bout Bob Rinderle? Clyde Duensing?

LLoyd

Unpotting a transformer
 

On Mon, 20 Apr 2009 17:51:02 -0500, RoyJ
wrote:

I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time.
But the whole transformer is potted in some sort of black tar. I scraped
some of it out, looks like it softens at 200F, goes semi liquid at 250F,
and fully liquid at 275F. Easy enough to rig a tent over a catch basin
and aim a heater in there but what about the temp rise on the wires? I
would need to run it at the 250F to 275F (120C to 135C) range for
perhaps an hour to get all the goo out.

Why do you need to de-pot the transformer?

Unpotting a transformer
 

Size, heat dissipation, plus the case has two sections (the other
section is for the defunct timer and photocell circuits), I will only be
using 1. OK, the real reason is that all that goop offends me!! :)

Don Foreman wrote:
On Mon, 20 Apr 2009 17:51:02 -0500, RoyJ
wrote:

I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time.
But the whole transformer is potted in some sort of black tar. I scraped
some of it out, looks like it softens at 200F, goes semi liquid at 250F,
and fully liquid at 275F. Easy enough to rig a tent over a catch basin
and aim a heater in there but what about the temp rise on the wires? I
would need to run it at the 250F to 275F (120C to 135C) range for
perhaps an hour to get all the goo out.

Why do you need to de-pot the transformer?

Unpotting a transformer
 

On Sat, 25 Apr 2009 09:08:01 -0500, RoyJ
wrote:

Size, heat dissipation, plus the case has two sections (the other
section is for the defunct timer and photocell circuits), I will only be
using 1. OK, the real reason is that all that goop offends me!! :)

Ah! So you don't need or plan to separate the lams for a rewind.

AxMan often has Cadmium Sulfide photosensors. So does Radio Shack.

Unpotting a transformer
 

This unit has 2 circuits, an integral timer circuit, photocell, and
solid state relay programmed with a single button that is potted in the
other compartment of the case. I don't really need the unit for it's
original purpose, just wanted a clean 28/24 volt CT 25 amp transformer
for other projects.

Hampton Bay sku 591-331 vendor # RK610543 mfg 06/04 I presume it is from
Home Depot.

Don Foreman wrote:
On Sat, 25 Apr 2009 09:08:01 -0500, RoyJ
wrote:

Size, heat dissipation, plus the case has two sections (the other
section is for the defunct timer and photocell circuits), I will only be
using 1. OK, the real reason is that all that goop offends me!! :)

Ah! So you don't need or plan to separate the lams for a rewind.

AxMan often has Cadmium Sulfide photosensors. So does Radio Shack.

Unpotting a transformer
 

On Sat, 25 Apr 2009 11:52:31 -0500, Don Foreman
wrote:

AxMan often has Cadmium Sulfide photosensors. .

What a neat place to go rooting in. My son introduced me to it when I
visited him at the Univ of MN when he was there for a summer
engineering program a couple of years ago. That and Cheapo, the used
CD place.

RWL

Unpotting a transformer
 

GeoLane at PTD dot NET GeoLane at PTD dot NET writes:


On Sat, 25 Apr 2009 11:52:31 -0500, Don Foreman
wrote:

AxMan often has Cadmium Sulfide photosensors. .

What a neat place to go rooting in. My son introduced me to it when I
visited him at the Univ of MN when he was there for a summer engineering
program a couple of years ago.

"There's no place anything like this anywhere near here,
so this MUST be the place..."

It's been decades, but I recall the ?almost? free sodapop...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Unpotting a transformer
 

replying to RoyJ, justme wrote:
RoyJ, I know that it's been almost a decade since this project started, but
could you please confirm if getting the black goo out makes the transformer
reusable? I have one and would like to rewind it, but would like to know if it
worth the trouble before breaking it apart...

--
for full context, visit http://www.polytechforum.com/metalwo...er-178168-.htm

Unpotting a transformer
 

On Mon, 15 May 2017 13:18:02 GMT, justme
wrote:

replying to RoyJ, justme wrote:
RoyJ, I know that it's been almost a decade since this project started, but
could you please confirm if getting the black goo out makes the transformer
reusable? I have one and would like to rewind it, but would like to know if it
worth the trouble before breaking it apart...

Usually, one determines the need to unpot an xfmr -because- that the
xfmr tested out shorted/open. That generally means it will need to be
rewound.

One seldom unpots working devices. It's too much of a headache to do,
especially when the component is destroyed in the attempt to get the
black goo off it. Most potting compounds are serious bitches to
remove, and most solvents can destroy the components before they even
touch the potting compound. g

Trying to unpot the bottom of a board just -to- test it can destroy
the board, as well. Potted things are most often tossed.

--
In today’s academia and mainstream media,
we’re all guilty of hate until proven leftist.

--Robert Knight, senior fellow, American Civil Rights Union

Unpotting a transformer
 

On Mon, 15 May 2017 13:18:02 GMT, justme
wrote:

replying to RoyJ, justme wrote:
RoyJ, I know that it's been almost a decade since this project started, but
could you please confirm if getting the black goo out makes the transformer
reusable? I have one and would like to rewind it, but would like to know if it
worth the trouble before breaking it apart...

Unless the transformer is utterly positively unique and another one
cannot be modified and installed..or simply new holes drilled and a
new transformer installed...there is absolutely no reason to repot
one. Not unless you are trying to restore a 1901 Bramford 10 three
sided spoke shave with optional threading, back to exactly original
condition.


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Unpotting a transformer
 

On Mon, 15 May 2017 13:18:02 GMT, justme
wrote:

replying to RoyJ, justme wrote:
RoyJ, I know that it's been almost a decade since this project started, but
could you please confirm if getting the black goo out makes the transformer
reusable? I have one and would like to rewind it, but would like to know if it
worth the trouble before breaking it apart...


for full context, visit
http://www.polytechforum.com/metalwo...er-178168-.htm
What possess designers to use light Gray text on White background?


Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place



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Unpotting a transformer
 

On Tue, 16 May 2017 08:23:16 -0400, Boris Mohar
wrote:

On Mon, 15 May 2017 13:18:02 GMT, justme
m wrote:

replying to RoyJ, justme wrote:
RoyJ, I know that it's been almost a decade since this project started, but
could you please confirm if getting the black goo out makes the transformer
reusable? I have one and would like to rewind it, but would like to know if it
worth the trouble before breaking it apart...


for full context, visit
http://www.polytechforum.com/metalwo...er-178168-.htm
What possess designers to use light Gray text on White background?
Boris Mohar

Boris, every time I see a site like that, I write to their CS and tell
them to buy their web designer a copy of Jakob Nielsen's wonderful
book, entitled _Designing Web Usability_. If nothing else, give text
some contrast from the background color, please!

--
In today’s academia and mainstream media,
we’re all guilty of hate until proven leftist.

--Robert Knight, senior fellow, American Civil Rights Union