Taking apart/re-winding an OT

[MitchK]

SO I've got a bunk OT pulled from my JCM 800 2203. I'm currently trying to take it apart so I can attempt rewinding it, but I'm running into a problem. I'm trying to take the laminations apart, and I can get the L brackets off but I can't get a single E bracket to come up I guess because I can't crack the resin thats in the middle of bobin? Any suggestions? I'd soak it in mineral spirits or something but I'm hoping that I will only have to rewind maybe one of the taps or something.

[nico.verduin]

You'll probably have to try to loosen it (1st laminate) with say a sharp knife and try to get it out . The rest is usually easy.
Nico

[MitchK]

well the problem I'm having is that I can get all the L sections off but I can't get the "E" brackets off, the sides are fine but its that middle piece that goes into the bobbin that I can't get, I can't even get one of them off, the knife can't get at it inside the bobbin.

[nico.verduin]

Try to fix the bobbina nd hit it out with something like a small screwdriver maybe?

[Gregg]

Do us a favour - take notes and post a diagram how the transformer is wound - number of primaries and secondaries, interleaving, number of turns etc.

[MitchK]

For sure Greg, give me specifics of what you want though.

as for popping the bobbin out Nico, you can't actually do that because the order of which side the L or E laminate is on alternates. Picture and E and then a backwards E and then slid them together, see what I mean?

[Gregg]

If the transformer is epoxy potted or something there's no way to disassemble it. You'll have to cut it which means to destroy it /the laminations/. If this is the case and you still succeed to take it apart you can't use the laminations anymore because ther will be lacker /or whatever/ left and they won't stick to each other properly. So if you can't use the OT in it's current condition and the thing are heading to destruction do us a favour by taking detailed notes and pictures unwind it layer by layer and post the winding configuration, number of turns and so on. If you can't do it send me a personal message and we can arrange you to send me the bobin - I'll do it myself.

[MitchK]

I really don't think its epoxy, unless it would be just inside the bobin? whats on there is a reddish color and does not smell like epoxy
. I really can't figure out how to pop these things, I've tried taking one of the long break off razor blades and sticking the blade down between two laminates to try to maybe cut away at the resin in between but it doesn't really feel like its doing anything.

Here is one of the L brackets:



you can see the resin on it,

here is the core, notice the lip on the bobin, that makes it hard to flex the middle part of the E bracket:



and the last one just a general shot, you can see along the edges where I've loosened some of the laminates all around but still I can't pull them out because of the middle of the E bracket:

[nico.verduin]

You might try a "paint"store if they have something to remove the "lacquer". This transformer has definitely been vacuum cooked in lacquer at the looks of it. I'm not sure if any lacquer dissolvent exists. Maybe a "paint remover" don't know if they sell (or are allowed to) selll the stuff in the US. I would also be interested in the coil assembly btw.
Nico

[Steve Conner]

You could try heating it (in as hot an oven as you dare, for several hours) to soften the lacquer, then trying to lever it apart while it's hot. Once you've got a couple of Es out, the rest will come much easier.

I'd also be interested to know the number of turns, interleaving, and what have you.

[Gregg]

From what I see the transformer has been "cooked" and this is a standard procedure against moisture /and other things/. I"ll repeat myself by saying that even if you manage somehow to disassemble it the laminations will be practically useless which is not so bad because with the free coil available you'll be free to try other same size laminations and who knows - maybe you'll like your new OT better. My advice is to cut it and save yourself some sweat.
If you choose to proceed with unwinding the coil please take detailed pictures and if you can't measure the thickness of wire and insulation make sure to take samples. If you don't know what exactly to do I'm sure we have here people who can help you with that.

[MitchK]

You could try heating it (in as hot an oven as you dare, for several hours) to soften the lacquer, then trying to lever it apart while it's hot. Once you've got a couple of Es out, the rest will come much easier.

I'd also be interested to know the number of turns, interleaving, and what have you.

hmm interesting I'll try that, but won't the paper on the bobin burn up?

[MitchK]

Gregg, I don't see why the laminations will be useless, I mean I can appreciate how tedious it will be to re-assemble but you know, its something I'll do over a long period of time.

And also, do you or anyone else know where I can actually buy laminations?

[R.G.]

Nota Bene: The insulation on the laminations is likely to be heat-formed blue iron oxide. The "lacquer" is transformer varnish, one of a number of varnish-like compounds used to impregnate transformers to keep the coil wires from moving around, improve heat transfer out of the transformer, and exclude moisture.

You CAN get one E lamination out. It just takes some time and willingness to destroy one and only one if that's what it needs.

[MitchK]

Nota Bene: The insulation on the laminations is likely to be heat-formed blue iron oxide. The "lacquer" is transformer varnish, one of a number of varnish-like compounds used to impregnate transformers to keep the coil wires from moving around, improve heat transfer out of the transformer, and exclude moisture.

You CAN get one E lamination out. It just takes some time and willingness to destroy one and only one if that's what it needs.

ah R.G. you sound like you know what you are talking about. Any particular strategy you'd recommend? should I go for the outer most one or a few in? what do you recommend, just take the vice grips to one and yank on it like my life depends on it? what about the idea of heating it up, or perhaps freezing it so the varnish becomes brittle? should I try cutting away at the varnish with a razor?