Help needed with transformer laminations

[retailer]

Does any one know how to dissassemble this transformer - it's about the size of a matchbox. I've taken apart and re-purposed many EI core transformers, once you get the first 2 or 3 laminations out the rest is easy. This core (and the one next to it) has one piece laminations I think I recall seeing them referred to a M type laminations - I could however be mistaken. If the laminations are indeed M type then the only way I can see that they can be removed is to bend the outside up and over the bobbin/windings so the centre leg can be slid out, being soft iron the lamination would stay bent, am I correct.

[Diabolical Artificer]

Blimey, those bolts are tight, problem with buzzing in the past? Looks like you'll have to cut the windings.

Andy.

[retailer]

Both of the transformers were pulled from a partially dismantled piece of Telefunken audio test gear found in a dumpster, not sure if they buzzed. EMT is a German manufacturer of high grade studio recording gear so I'm assuming the laminations are a decent grade. I was hoping to not have to cut the windings as that would probably mean the bobbins would be destroyed in the process.

[Refugee]

It looks like it is not impregnated with anything that would be difficult to remove.
The easy way would be to remove the bolts and gently tap it on a bit of wood and see if the laminates move. They look like they are already parted at the edges.

[Diabolical Artificer]

There must be more than meets the eye with these tfmrs. They either come apart somehow or they were wound around the lams, but why? Why go to that trouble and what benefits would one piece laminations afford. It's a puzzler.

A.

[joebog1]

Er hmm WHY do you want to pull it apart? A transformer that size will be "BIG SCARY" on the inside. Even if it's a matching transformer there will be many turns, if not many hundreds of turns of very fine wire.

If they dont work, OK I would consider the job myself. BUT after designing and making transformers for over 50 years, I would want to know why they need disassembling?

Joe

[Radio Wrangler]

It could be U and T laminations with the join under the paxolin pieces. I've seen O and I lams as well.

One piece laminations are as much of a pain to wind as toroids, so you might just as well make a toroid, and the steel becomes a simple wound strip.

I think this could be O and I with the centre bar press-fitted and those screws holding it in place.

David

[FRANK.C]

I have come across one piece laminations in the past. If it is the type I am thinking of they come apart as Retailer describes in the opening post. The metal was fairly springy and the laminations fitted back together without any problem. I think they were fitted in a Radiola radio

Frank

[vidjoman]

Looking at the last picture you can see the central core - look at the silvery part by the large bracket.

[ms660]

I wonder if the center core is totally separate laminations and is just a push/press fit, looks like locking/stop tabs in the last photo?

Lawrence.

[Leon Crampin]

The standard German laminations of this period were a complete window stamping with one break at the end of the central limb, adjacent to the bobbin cheek. They are fitted by lifting a lamination at the opposite end to the break and pushing the central limb out of the bobbin whilst the lifted end passes over the outside of the bobbin. It's far easier to do than to describe. Successive laminations are reversed so that the air gaps are staggered at either end of the central limb. Assembly and dismantling are very easy once you get the knack.

It's an excellent system, giving about the lowest air gap loss possible short of a toroid. The downside is that the laminations are not scrapless - so there is a waste of material.

Beware 220V transformers - some saturate on our 245V mains. (maybe not at this time of the year though).

Leon.

[Leon Crampin]

Correction: begin by lifting the lamination at the same end as the break.

[retailer]

I thank all for the replies. Having previously taken the bolts and the metal mounting bracket off I think Leon must be correct, I thought there may be a way to dismantle without bending the laminations but it looks like this is the way to go.
Having taken EI type cores apart before I have found the first few lamination invariably get bent and it is nearly impossible to get them flat and straight again so I just leave them out. I was concerned that if I bend these laminations I may not be able to get them straight again.
For those that want to know I'm in the last stages of building a LA2A compressor/limiter for my son and while I have a few mic and line level transformers none of them are suitable as an output transformer - they have either incorrect impedance or poor frequency response. I plan to use one of these cores to wind a suitable output transformer, they are the right size (50mmx40mm) to fit inside a shielded case I have and coming from a respected company I reasoned that the laminations would be decent quality. It's been a while since I removed them so I don't recall if they were connected to mains, but having come from 1950's era valve gear I don't think being the size they are that they were used for mains voltages.
Windings with thin wire like 36 or 40 SWG don't scare me, just need to take a bit of care, however these cores are big enough so that I doubt I'll have to use wire that thin. I've never done line level or mic transformers before but I can't see it is any different from say a regular hifi type output transformer.

[Refugee]

I have had a closer look at the photos.
The lams are not the common shapes as there appears to be gaps at opposite corners.
Perhaps they might be F shape and L shape alternately.

[retailer]

As Leon said they are one piece and relatively easy to get apart (thanks Leon for giving me the confidence) they are quite springy and not what I would have expected - even though they are short and I had to bend them around 1/2 inch to clear the bobbin they have sprung back to a flat lamination, I assumed laminations would soft iron and once bent would remain so. They quite thin .015 " or around .38mm. The laminations have a gap (visible) and all laminations were oriented the same way leaving a gap in the magnetic path so I assume that transformer would have been able to tolerate a small dc bias.
The bobbin looks to be made up of the ends or cheeks plus 4 central pieces that make up the winding tube - if that is what it is called, 2 of the central pieces have locking tabs that stop the cheeks from spreading, one extends up and carries the terminations, it does not look to be glued together and once I remove the wire I expect it will come apart like a puzzle toy. I did how ever damage the locking tabs on one of the pieces trying to get the first lamination out, they don't look too difficult to duplicate once I source some suitable material