Electronics 2000

I have been asked to help out with a project which is pretty straight forward, however I am looking for someone to wind a couple of audio transformers.This is not an
easy task as they require around 800-1000 turns of primary and secondary windings using 40 SWG copper wire onto a ferrite core bobbin.
I am hoping I can be guided to a company or hobbyist who can take it on.

It may be better for you to see if you can buy something which will do the job. I have just looked on Google for "small audio transformers", and quite a lot came up.

Thanks David.I will look it up but do not hold up much hope for something off the shelf at this stage, as this has to be wound with exact parameters to be part of a tuned circuit around 2000 c/s. The signal coming in is no more than 2-3 millivolt... yes really that small,and then go to an amplifier. As this is a prototype I may have to resort to winding them myself, and then go on to see if I can locate parts to do the job.

This sounds as if it is a very interesting project. Perhaps you could post some more details, with a schematic? (Just say no if you need to keep the details under wraps).

This project is a Proton Magnetometer and available to anyone to develop. I built one many years ago- worked well- but
now needs the circuits brought up to date,as some parts are no longer available. This has been attempted,and circuits are
out there, but in my opinion the one I recently built needs work on the front end, to make it work as the original design.

That is where I am now. If interested look up on Google,and find the one by L.Huggard.

Thanks. I have read the article, and yes, I think you may well have difficulty in obtaining ready-made transformers. I remember (nostalgia trip here) that I saw a published article from which you could build a coil-winding machine with Meccano. Alternatively, there are coil-winders on EBay, some at only $30 or so. One of these may well help you.

Incidentally, which components are no longer available? The transistors could be easily replaced with newer ones, and the relay is surely a stock item. Perhaps you are thinking of using CMOS switches, op-amps in the amplifier section, and band pass filters to replace the coils and tuned transformers? That would be a redesign and a half!

I hope this helps.

Any help is appreciated.The transformer cores are the ones that are no longer available, but I have managed to find some
that should do the job and give more or less the same results.The design that I am using for the amplifier section has
been upgraded to use op-amps and band pass circuitry but does not give the stated results. That is why I need to work on
the front end.The signal is there but needs coaxing out.

Mmm - yes I cab see that the pot cores might be a difficulty. If you did want to source some, perhaps you could try some of the sites on the web dealing with vintage electronics? Somebody surely will have a stock available for sale or exchange.

Thinking again about this, I am wondering if it is necessary to use pot-cored transformers at all. Why not try connecting the water bottle coils to the inputs of op-amps (taking care of the DC levels and AC gain, of course) ? That should give you a lot of control on the parameters of the front end of the whole system.

Your thinking is correct. The design I am using, does not call for transformer on the input. If you would like to see the complete project go to this link.https://www.scribd.com/doc/45216755/Magnetometer