Toroidal transformer

I have used Antrim Transformers for small-volume (including 1 off) mains transformers for Hobby Audio projects in the past, and been happy with the results. These ranged from 70VA to around 700VA IIRC.

It looks like although Antrim transformers are still going, under the Trans-tronic umbrella:

you might be better off with 'Canterbury Windings', which I think was the chap I actually used to talk to:

You probably know this but you need to pay attention to loading etc. when specifying the actual voltage, especially for small VA xformers. Terry could advise you, I'm sure.

HTH Jon N

Is a torroid necessary?

You used to be able to get kits for standard E-I laminated transformers.

I'd also be concerned over mains voltage variation. One trick is to factor in the 10% or so regulation you get with transformers and go up one size.

How about a 9-0-0 volt toroid with a few extra turns overwound to give you the 1 volt per side?

Charles f

Ah - that explains things. Pretty sure it was them I got the ready made one from - but couldn't find them this time. Thanks.

Yes.

Why?

That would be the way I'd do it for hobby use but not really acceptable professionally.

Size. And low external field.

usually for low external hum field and tighter dimensions - more power per cubic inch etc.

I'm aware of those features, just wondering why they are so important as toroidals are much more difficult to wind.

Not if you have the right machinery. In fact they are easier than normal transformers to assemble - putting Es and Is in (or Ts and Us) is not that simple

CPC have 2 x 9 volt

Crovisa in Malaga have a 10 volt (230 volt primary)

Owain

Two smaller ones? Brian

I've always found them much better at regulation and can be fitted in areas that hum would be a serious issue with a normal one. I have a quite presentableGoodmans stereo system but the idiots put in a normal transformer, rendering the tape players useless. Looking inside at the time it looked to me like there were mounting holes for a torroid, but no doubt the bean counters could not afford one! Brian

Yes back in the 60s I worked at a place that had one of those machines, but it could only do very small ones. I never did figure out how it did it though. Brian

same as a sewing machine, you throw a shuttle through the middle wound with wire, and catch it the other side

We had one at a previous workplace. Wire is loaded onto a split bobbin which goes through the toroid. Then it is unloaded from the bobbin onto the toroid. There were also winders which used something like a bicycle chain linked though the toroid as a bobbin.

Here's one:

Ours was much smaller, and much faster.

I'm not worried about that as I don't intend making it myself. ;-) I'm happy to pay the same sort of premium over a conventional transformer.

When I bagged a 110v IBM colour monitor 'Bargain' at a radio ham rally about three decades ago, a 60VA toroidal transformer with split primaries was the only viable solution to powering it from a 240v mains supply.

My alternative open frame transformer solution otoh, located on the floor under the desk, was a "No Go" simply due to the effects of leakage flux even at this separation distance (nearly three feet!).

If you ever need a 'Testimonial' to the superiority of toroidal transformers over every other type in regard of compactness and low external field (particularly the practically *non-existant* external field), then I'm your man! :-)