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Alston
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Joined: 04/04/2021
Location: Australia
Posts: 63

Posted: 01:14pm 20 Dec 2021

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wiseguy said That looks very familiar - there is still a lot to do though. I reckon an angle grinder with one of those wood carving/shaving discs would remove a lot of that potting crap (along with a bit of varnish.....) in good time. That would also help simplify the energy needed during unwinding. You just need to be careful around near the inner 240V winding wires and where they exit.

I have a mandrel that looks just like that too

I'm curious how long did it take you to remove - I'm hoping you don't say 5 minutes..... mind you I was learning as I progressed.

It took around an hour to get that out so about the same as what you experienced. I tried an angle grinder over the weekend but it made to much of a mess.

Alston
Regular Member

Joined: 04/04/2021
Location: Australia
Posts: 63

Posted: 01:37pm 20 Dec 2021

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nickskethisniks said Let me nuance my 1h statement, this was done with a 1400VA transformer. Apparently there is a remarkable difference between a 1400VA transformer and the 2700VA transformer I did today, both potted with grey stuff. The difference between the 2 is that the bigger transformer has a much thicker layer of potting on it then the smaller one, it also has bigger gaps between the wires. This makes it a lot more difficult to go thru that stuff. I think I spent about 1h30 this time, but went for the core only. I tried some different things this time, like using a cordless drill hammer but I had the feeling doing it manually my strokes had more impact.

I lost time chipping of stuff on both side, you really only need to do 1 side first if you are not saving the windings. Then smashing as hard as you can on the middle part, it should come loose. Both windings were damaged this time, this because of the electrical hammer, and so I didn't try to safe the 230V winding this time. The wires of mine were very thick, 3.4mm for the low voltage winding and 2.75mm for 230V. The 230V winding was on the outside of the core so I couldn't save it.

You could ask yourself if it is worth the effort, better to source a non-potted transformer for sure. But over here I can't buy those cores, and should import from UK.

I forgot to take pictures, but this was the battlefield:

Reward : 220*120*70

So you essentially use a chisel to cut through the winding all the way until you get to the core, then sort of wind you way around the outer diameter and the the inner one until you can take the top off and the core comes out?

Alston
Regular Member

Joined: 04/04/2021
Location: Australia
Posts: 63

Posted: 05:54am 24 Dec 2021

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Well it wasn't easy but I got it apart. Using the chisel method was definitely the right way to go. I don't think I would want to do another one!

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