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Old 25th November 2010, 05:25 PM   #11
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Smile Removing transformer varnish-nasty chemicals

Strong, by now illegal chemicals work somewhat, but not to fully recover the laminations. I've only done this a few times to reproduce a fried transformers turn ratio and layering construction. Near impossible to get them clean enough for reuse. The magnetic path will never match the design using new stock. Residual gunk will not allow the lams tight coupling. Best bet is to try finding new stock.
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Old 14th April 2012, 06:54 PM   #12
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I recently took afairly big, old transformer apart by boiling it (on a low simmer) in ordinary drain cleaner (sodium hydroxide). I cooked it for several hours, turned the heat off and left it on the stove until the next day. The liquid solution we buy in Denmark holds 40 % weight/volume and that should probably be diluted to about a quater to half that strength. I used the solid stuff and added that to some water in the pot.

WARNING: People who are chemists (I am) can skip this paragraph. Others should know a few things about this chemical before working with it: 1) Always wear safety goggles! (This stuff is nastier than battery acid in terms of burns. It is also much harder to rinse off as it turns the fat in your skin into soap and it penetrates much deeper). Rubber gloves and a plastic apron are prudent measures, too. Your prime concern is not to get the stuff in your eyes or face. 2) It evolves much heat when poured into water. Don't add too much too fast or it may boil violently and spray drops on you. Add the concentrated drain cleaner into the water. Never do the opposite - the heat can get out of hand. Your prime concern is not to get it in your eyes or face. 3) Do NOT use an aluminum pot. Drain cleaner, especially when hot, attacks aluminum ferociously. The pot will dissolve and the reaktion evolves hydrogen (explosive gas). You can safely use most other metals. And glass lids are also safe to use. Steel or stainless steel and glass is left unharmed, though very clean. 4) Sodium hydroxide is not poisonous. It burns, so don't drink it, of course. But, once the pot is rinsed it will be perfectly safe to use for food afterwards. Small dilute traces of it will not harm you in any way. 5) It does not emit any harmful vapours or gasses (if you keep it away from aluminum). If you smell anything, it is just the laquer getting broken down.

(Back to the subject): The laquer dissolved completely on the outsides of the transformer and softeded to a slime, gel or gum on the inside of the coils, dependig on how well it had permeated.. The laminations were really easy to pry loose with a stanleyknife afterward. Only the first layer needed a bit of chiseling with a hammer and screwdriver because of the physical tightness. I was even able to salvage most of the magnet wire in a reusable condition. Apparently the insulation laquer on the wire was indifferent to the drain cleaner. (I wouldn't bet on it, though. So I'm not going to use it for anything high voltage). The whole dissasembly operation was performed in the kitchen sink under gently running water to prevent caustic burns on my fingers.
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Old 20th April 2012, 03:59 PM   #13
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Default Warnings about trying to re-use lams

Some of the suggestions are valid, especially meth-chloride, for removing the varnish. Any material that is caustic enough to remove the varnish is surely going to damage the wire and bobbins. I have another warning: If you intend on recycling the lams to build more transformers, don't expect the same performance, in fact, they may not work at all. Laminations receive an oxide-style coating referred to as "core plate, C5, etc." This coating is important as it separates the individual laminations which minimizes the eddy currents, hysterisis losses and core losses. It also minimizes the excitation currents. All of which minimizes the input currents, under full and no-load. Removing the coating may increase the losses to a level that causes the transformers to overheat. As a minimum, you may end up wasting time building a transformer that you can't use.
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Old 20th April 2012, 04:45 PM   #14
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Location: Barrio Garay,Almirante Brown, Buenos Aires, Argentina
Here in Argentina there exists a product called "Cloroformo técnico" (Technical chloroform???) and that is buy in the chemical sales in galss bottles, that dissolves very well the varnish, but don´t affect the coil wire nor bobbins. I use it several times to disassemble ferrite transformers from PC monitors and TV and reuse them. About a night it takes to its job, and works pretty fine.
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Old 7th August 2013, 10:50 AM   #15
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we have been using this product and they're just fine. less evaporation but need to have gloves on.
IECCO
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Old 16th December 2013, 06:53 PM   #16
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Tetrahydrofuran - Wikipedia, the free encyclopedia. One of the best solvents for almost any kind of plastic, lacquer and varnish. Extremely dangerous, practically "dissolves" your skin, not to mention its fumes, so be VERY careful using it!!
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