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.

Reply to
RoyJ
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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.

Reply to
VK3BFA

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:

Reply to
Pete C.

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Indicates a max working temp of 130C

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Has a higher temp.

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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

Reply to
Wes

So what is your question, Roy?

The potting material sounds like Minerallac.

Reply to
Don Foreman

RoyJ fired this volley in news:7ZmdnXdARuEmqHDUnZ2dnUVZ snipped-for-privacy@earthlink.com:

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

Reply to
Lloyd E. Sponenburgh

Did you know George Roach?

Reply to
Jim Wilkins

Jim Wilkins fired this volley in news:7eee5e00- snipped-for-privacy@d7g2000prl.googlegroups.com:

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

Reply to
Lloyd E. Sponenburgh

Why do you need to de-pot the transformer?

Reply to
Don Foreman

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.

Reply to
Don Foreman

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.

Hampt> >

Reply to
RoyJ

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

Reply to
GeoLane at PTD dot NET

"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...

Reply to
David Lesher

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...

Reply to
justme

for full context, visit

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What possess designers to use light Gray text on White background?

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

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void _-void-_ in the obvious place

Reply to
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!

Reply to
Larry Jaques

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