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Toroidal Mains Transformer

Mains Transformers – Finding an economical source

Where to Buy Mains Transformers

So now you have built your circuit and need a cheap mains transformer to power it. The bad news is that even ‘cheap’ transformers are no longer found on the supplier shelves. By cheap, I mean more economical alternatives. For smaller circuits the tendency is for the user to buy an off the shelf SMPS – the entire supply which for instance can be a 12V 5A, is cheaper than a 12V 1A EI laminated transformer. The pricing has become that ludicrous. There, all along you thought that transformer manufacture was an automated process. Reduction in costs right?

Mains Transformers - Toroidal Mains Transformer
Small Toroidal Transformer (source BillC – Wiki)

Mains Transformers – still better than SMPS

As it stands and I don’t think I am alone in this thought process, laminated and toroidal transformers are more reliable than SMPS, they handle overloads better and are less noisy. Years back we all used English built Douglas transformers. A 200VA device was a large unit. Nowadays the 500VA transformer, a ‘cheap’ Asian import is the same physical size. So if the metal used is the same, the copper comes from South America and the process is nearly all automated why aren’t there more home built transformer companies. Doing a web search will bring up myriads of the ‘big guys’ – all manufacturing transformers in the kW to MW range. Now I can understand the logic here – there is more profits to be made. But what about the home user, the guy looking for a cheap transformer.

I opened a multi-purpose NiCad charger which cost 10$. The transformer was a laminated device with a 12V 1A secondary (assumption by weight, core size and diameter of wire). The same transformer at a popular outlet costs 19$. What to do, what to do?

Winding vs Buying

Although I have the expertise to wind my own transformer, which I have done in repairs years back, it’s time consuming and seldom looks as good as the original. A 300VA toroidal with 30-0-30 secondary costs 100$. A local manufacturer will build you a 1KVA laminated unit for the same price. Audio people like toroidals for some reason or other. There are also audio people that reckon they sound no better than the laminated variety. Toroidals are now also wound through an automated process but their prices have not dropped. In fact they have increased. The excuse is always around copper prices. Just how much did that 2lbs of copper cost then? Buy a 5m length of wire from an outlet specialising in electronics and make a comparison when purchasing 100m from a specialist supplier. In my case, the specialist supplier of 1mm enameled wire was 1/10 the price. And they are still making a profit but on volume. I’m not knocking the electronics shop on the corner – they just don’t move volume.

Shipping Weight of Mains Transformers

Recently I was interested in purchasing a vintage EL34 amplifier off eBay. Amplifier 300U$, shipping over 300U$. Weight is the factor. It’s the factor when importing transformers as well. Transformer design is not a new invention – we cannot build a mains transformer of 1kVA anywhere near the same quality as a specialist. Locally (Cape Town, South Africa) I was quoted 200U$ for 2kVA. This is a very reasonable cost compared to a supplier of 300VA transformers at 100U$ each. 1$ per VA compared to 3. The one specialises in transformers whilst the other does not. Admittedly it’s laminated vs toroidal. Local vs import. So where to from here?

It would be really neat if transformer manufacturer’s could add their company names to our database. In South Africa we have the following reputed companies supplying mains transformer for the DIYer and professional electronics companies:

  • Eloff Transformers – Cape Town (very good alternative to buying ready made, off the shelf)
  • Communica – Cape Town, Pretoria
  • Mantech – Cape Town, Johannesburg
  • Yebo – Cape Town (Plumstead & Bellville)

This listing does not cover all suppliers but the ones which are more common in Cape Town. What about the other regions? Nationally and Internationally? Parts-Ring is not a local or regional directory listing as such, here we have discovered an area of considerable weakness (that of lower VA rated transformers)  – the most expensive component in most projects is going to be the mains transformer, whether 50/60Hz, high frequency, laminated, ferrite or toroidal.

List your business here: (note: if you have not registered as a user yet first you will not have access. If this is the case, go here)

Practical website, strong search and pricing is Farnell:

To finish off, I do believe that as time has moved on mains transformers have become just too darned pricy to believe that margins have remained the same. Local manufacture is key, importing is costing just too much.  Sometimes to finish off a product one needs to dismantle a most usable item for that most important of components – the mains transformer.




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