In the refurbishing business, you are likely to come up against this problem. There are a few options.
*Is it possible to get the same piece of used equipment which has a working transformer.
*how much space do you have, you may be able to use a couple of transformers in the place of one, since the cores sizes will be smaller if you split the voltages over two, you then have a good chance of buying two transformers that will supply what you need (have a look at element14 catalogue for suitable units, for example).
*wind your own. If the existing transformer is not potted, then use the core on which to rebuild it (see comments below on sources of materials). Other option is to buy a new transformer with the correct power rating, in which the lamination's can be removed. The secondaries need to be on the outer part of the winding(typical), or on a split bobbin, which is preferred. Knowing the ratings needed for each winding, you can put the required number of secondary winding's on, with the appropriate magnet wire. You will need suitable insulating materials (elephant/kraft paper and 3M transformer tape)between secondaries (and between primary and secondaries if the bobbin is not split) and wire, a transformer manufacturer may supply these. Element14 and hobby electronic shops also sell magnet wire, for example.
If the transformer has a single bobbin, and a screen between primary and secondary, you can buy copper or brass shim, remember not to allow this to form a shorted turn, the ends must be electrically isolated form one and other.
Best I can do, hope that helps,
cheers,
Richard
