Testing/replacing transformers

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Brandon Hartwick

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Hey guys

I'm working on a pair of power supplies and crossovers from a Quest that actually belong to another member here. Does anyone here have any idea where/how I can spec these for replacement? At least one of these was damaged from an amplifier that decided to violently pack it in.

I have already talked to Martin Logan and they have basically zero info on this speaker anymore and the transformer part number turn up nothing. If anyone can help shed some light on this I'd appreciate it.
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Russr

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Australie? You could probably find a transformer winding company that could whip up a couple and be ready before you get them from Oz, probably for cheaper...

Assuming we still have local shops that still wind transformers these days! I just did a search here in Houston for "transformer winding" and quite a few came up..
 

JonFo

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Ah, ESL step-up transformers, we've covered this here before. Such as this thread: Replacing / Upgrading Transformers

One of the conclusions was that Amplimo transformers were a good upgrade, such as this 1:75 (pretty close to the 70 listed on your schematic) would work https://www.amplimo.nl/images/downloads/esl/st106pp.pdf

Now, the challenge is finding some, as I think they stopped making those.

Also, paging @Jazzman53, who has used readily available power transformers in his custom ESL build, as he may have some thoughts on this topic. We discussed his choices here: Another ESL Project
 

Jazzman53

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Brandon Hartwick

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You want two of these per speaker, wired in tandem with 6V windings in parallel on the input side and 230V windings in series on the output side, and bias supply center tapped between the two 230V windings. That will give a 76:1 winding ratio (about 68:1 actual voltage step-up, accounting for losses). These work fantastically good!

Vigortronix VTX-146-050-106 Toroidal Transformer 230V Single Primary 50VA 0-6V | Rapid Online
That's a really good price actually, I'll have to look into those further. The closest the Aussies had was 100:1, no big deal as I'm going active anyway.
 

Jazzman53

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I wouldn't be surprised if those cheap power toroids sound better than the originals. I wasn't kidding about them sounding really good. I've used them for over ten years and fed them ridiculous power and never fried one.

I've used them in about ten sets of speakers and the only problem I ever had was one had its red & black wire leads reversed, which reversed the phasing between the windings and I got no sound output. I found the problem in a phasing test though, then swapped the leads and it plays perfectly.
 
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