Isolation Transformer Build - Technical Questions

[eccerr0r]

Re: Isolation Transformer Build - Technical Questions

Ah interesting, I would have thought the low cost units should be using EI cores as they're much cheaper to wind. Toroids, these are kind of tough...

[dicky96]

Re: Isolation Transformer Build - Technical Questions

Probably you guys are right, it's an autotransformer with no isolation. They sold a lot off that listing on ebay and are not clear what they are selling - I do hope someone does not get killed

As I already mentioned your best bet if you are in the UK is get two of the 110V portable site transformers and connect the secondaries in series (get the phase right)

These transformers regularly turn up on ebay or gumtree second hand and sell for £20-£30 and give good isolation (they are specifically designed as safety transformers). You can also use two of these as 110V-0-110V

Another good cheap source for very powerful transformers is scrap disco/club power amps. Get an old amp with linear PSU something like a 1200W - 1500W per channel and you will usually find a large toroidal with 90V-0V-90V or thereabouts. Old Peavey and InterM Amps and similar are a good source of these. That will give you 220V in 180V out at high ampage and that is close enough yes? plus you also have the input antisurge/filter, switch and power connectors to reuse.

[clearchris]

Re: Isolation Transformer Build - Technical Questions

I'd rather repair an old amp! I'm always scavenging ebay looking for old peaveys, but they are going up in price...

[dicky96]

Re: Isolation Transformer Build - Technical Questions

Well yes Chris, but sometimes they are beyond fixing... I did fix my Peavey's and sell them before I left the UK. They were Class F or G - which is the type which switches the HT+ between about +/-45V and +/-90V rails on the fly?

Anyway they had some damn good transformers in them. Mine just needed replacement main capacitors on both sets of voltage rails so were fixable

[clearchris]

Re: Isolation Transformer Build - Technical Questions

I can't imagine how bad they must be to be unfixable. Generally, they look like simple designs with simple parts. Don't know what kind they were, I just recapped them and replaced the volume pots. The pots almost always get busted in shipment.

Probably true for other brands though. I only touch peaveys. They are reasonably priced and usually built solid.

[dicky96]

Re: Isolation Transformer Build - Technical Questions

Oh yeah they were Class G

https://cdn.badcaps-static.com/pdfs/...3faf6720fd.pdf

However I will bow to better knowledge (or morals)

I recommend to go find some faulty/scrap old PA amps and in them you will find some very good transformers for the purpose of AC isolation 240V in 180V or so out

But if by chance they are Peavey then send them over to Chris who will probably be very grateful and give you enough money towards a proper isolation transformer

That should keep everyone happy yepp?

[clearchris]

Re: Isolation Transformer Build - Technical Questions

Heh, haven't bought any in a while, my favorite models seem to be well loved by others, and the price keeps going up on 20-30 year old peavey amps... Go figure.