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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
snipped-for-privacy@wia.org.au wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

So what is your question, Roy?
The potting material sounds like Minerallac.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

you

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Apr 21, 7:01am, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:

Did you know George Roach?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

http://www.minute-man.com/acatalog/Enamel_Coated_Magnet_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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Why do you need to de-pot the transformer?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 25 Apr 2009 11:52:31 -0500, Don Foreman
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
GeoLane at PTD dot NET <GeoLane at PTD dot NET> writes:

"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 snipped-for-privacy@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 15 May 2017 13:18:02 GMT, justme

for full context, visit http://www.polytechforum.com/metalworking/unpotting-a-transformer-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
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 16 May 2017 08:23:16 -0400, 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!
--



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

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.