Taking apart/re-winding an OT

[Steve Conner]

Yes, heating it may burn things up, but you're going to be trashing the windings and starting again, right?

How about getting a cheap steel rule and using it with a hammer as a kind of very wide and flat punch, to hammer on the exposed centre leg of the first E.

Disassembling transfomers that have been vacuum impregnated is one of the classic problems in electronics. Every time I've tried it, I've ended up laying into the thing with a screwdriver and hammer, and sacrificed a couple of the laminations. I avoid it where possible. If I need a transformer core I'll salvage one from a transformer that's been cooked in wax or not at all.

[Gregg]

How about getting a cheap steel rule and using it with a hammer as a kind of very wide and flat punch, to hammer on the exposed centre leg of the first E.

I've done with transformers that have not been impregnated but it should work in this case as well. Maybe it will take more time.

[R.G.]

should I go for the outer most one or a few in?

Always go for the outermost one. That eliminates half of the impregnant (one side).
Take a razor knife or straight edged razor and cut into the crack between the first and second laminations. Loosen the complete outer edge all around the outside of the "E". Also try to loosen the end of the tongue where it goes through the bobbin. And then...

How about getting a cheap steel rule and using it with a hammer as a kind of very wide and flat punch, to hammer on the exposed centre leg of the first E.

... do this. Or use a large flat bladed screwdriver. Your razor will have loosened the outside. All that's holding it in is the adhesive on the inside of the tongue of the E, plus any mechanical pressure. Take a flat metal edge, put it right at the edge of the lamination's tongue and whack it with a heavy stick or hammer. The objective is not to bend the metal, but to apply enough modest shocks to crack the varnish that's holding the tongue to the tongue under it.

Remember that you may have to destroy one lamination to get it out. Destroy no more than one. In fact, before you start this whole process, get your mind into the set that you will spend a couple of hours, perhaps more, teasing this thing apart. Do not expect it to be simple. It's a game of inches.

If you can't razor-edge loosen the outside, chances are it's epoxy impregnated. You can still open it up, but it is so much work that it's not worth it. Varnish can be done, even though it's not easy. If it's epoxy, Just bandsaw the end of the transformer in four places to make the top and bottoms of the E's fall off and slip the bobbin off the remaining tongue plus ends. Get your laminations from a different transformer.

[Gregg]

Any recent developments?

[MitchK]

It may not be dead yet I'm now realizing, check my other thread out:

http://music-electronics-forum.com/s...3587#post23587

any help is appreciated.

[mykey]

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.

not worth it, buy a new one. the only time you rewind a tranny this small
is when its no longer available, or can't be substituted.

[MitchK]

more comments from the peanut gallery.

[mykey]

more comments from the peanut gallery.

comment from Marshall authorized tech with 34 years hands on experience.
and pretty good advice at that. There are over 10,000 turns of micro hair fine
wire inside, did you plan on doing this by hand? It's been tried before..............