btw I also got some ferrite toroids, but I dont know if those are of any use at all? They would be much easier to wind, and could be stacked.
Are you sure the toroids are ferrite? There are a lot of powdered iron toroids floating around, and it's not easy to tell them apart. If anyone out there knows how to use simple bench tests to differentiate between ferrite ans powdered Fe, please come forward and say.
You need to calculate the cross-sectional area of the toroid, make sure it's the same as that of the central post of the transformer you're replacing.
Do you have a source for ETD49 bobbins? Or just an approximate cost?
Aaaaaaah.... the bobbins.... Now you understand why it's important to preserve them (with the core they're on). This is an even more elusive product than the ferrite. They seem to be about $3 when paying an "authorized disributor's" resale list price. You can't easily find a distibutor that has them, and is willing to sell just two or three.
The bobbin mfr. I know about is Miles-Platts, in England. There are others, but this one is most prolific around ETD cores.
You might work backwards, from Miles-Platts (email them) and find out all the distributors in your area.
Dexter Magnetics in Chicago, carries the Miles-Platts line. They may sell you a small quantity, if you say you're an engineer prototyping a new design.
If other members are interested, maybe we can buy in quantity and spread them around.
The truth of the matter is that ETD cores are one of the most expensive tranformer platforms in SMPS, because of the intricate design of both magnetics, and coil formers. Plain old square "E" cores may be easier to work with.
And then again, you can make that bobbin yourself. Cardboard won't do, because the cummulative force applied to each turn of wire causes deformation of the former. Eventually, even a small deformation of the cardboard bobbin is enough to make it not fit onto the core any more.
A plastic tube, with flanges of epoxy fiberglass PCB material, makes a strong bobbin. (make sure there is no copper on that PCB --shorted turn.
Adrian