OT? DIY electronics?

Yes, they had this habit and this what led to their failure eventually. But it still was a very good magazine. The kits generated at one point

But, like I said, generating a pulsating square wave is not too difficult. The magnet and the coils are the difficult part.

I am not good at it. I did work for a few weeks for a company that made coils but I can't work out the formula around them if you paid me.

Buy some cheep Chinee guitar pickups

I am puzzled how you can claim I am "looking at the wrong therapy" when the NICE draft addresses a range of electrotherapies which explicitly includes "Pulsed electromagnetic field therapy" (PEMF). See e.g.

I may be looking at the wrong /condition/ but I didn't spot where you told us what that is.

Do you have a way to determine what 'correct' operation is? No reason you couldn't build something by trial and error if you had a field strength meter that could tell if you were producing a strong enough field. Once you have a suitable coil, design the rest of the circuit to drive it.

Even if you did the calculations, you'd still have to measure things - the actual inductance of a thing you built wouldn't match exactly the theory.

The '100 gauss' project uses a 40V 2A supply. I suspect such pickups would melt if that was applied to them.

Theo

That would end up about 1/4W.

I don't think so! They wouldn't draw anything like 2A

You could always rewind them anyway

What's a non-pulsating square wave?

I assume this is a kit where you purchase the parts including the GAL device?

?? There is no NE555 timer in the circuit in your link?

OOI, what was the fault? Whatever made you think it worked in the first place? Do/did have a means of measuring field strength?

What sort of therapeutic effect do you think it had (amusing it has worked)?

Given this is all a placebo effect, find an old telephone earpiece and convince them it's working.

SED is really more of a design group for pros (politics and trolls aside). However, I believe SEB has some of the more helpful pro designers from SED who are happy to coach amateurs, plus it's very much lower S/N ratio than SED. Or failing that, there are plenty of us electronics nuts here on DIY!