Euro-voltage PSU-Trafo for MkIII ?

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Euro-voltage PSU-Trafo for MkIII ?

Postby Cobra2 » Wed May 14, 2008 11:19 am

I have a pair MkIII, and need to convert them to 230V.
Is there any "drop-in" trafos for euro voltage?
Or could I power both original trafos in series with 230V?

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Postby TomMcNally » Wed May 14, 2008 1:48 pm

Arne ...

I think the series idea is a good one ... I see no reason why it wouldn't work.

Anyone else have an opinion ?

... tom
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Postby Cobra2 » Wed May 14, 2008 3:51 pm

About series, I'm a bit afraid for uneven load, but this can probably be adjusted with a shunt(resistor)...?

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Postby mesherm » Wed May 14, 2008 6:08 pm

I agree with Tom. I don't see why the two trannies in series wouldn't work,
assuming both are identical. Sounds like a simple but elegant solution.
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Triode Electronics has the solution

Postby EWBrown » Thu May 15, 2008 7:15 am

I wouldn't go with the series connection across 230VAC, that is just asking for something really bad to happen... :o With a possibility of 120VAC potential difference between the chassis, this could be an electrical disaster in waiting... :o There WILL be AC hum problems, galore. :o Light bulbs, maybe, but MK3s, never... Yellow_Light_Colorz_PDT_11

If you are a "purist" and want to preserve the looks and aesthetics, and don't want to mess around with external isolation or step down trannies, Triode Electronics does have a Euro-Voltage version of the P782 power trannie, at around $140 each, plus shipping:

http://store.triodestore.com/p782sexp.html


There is a Hammond "300 series" equivalent, the 378X, but the fit and finish are not identical, as the mounting dimensions are somewhat different. AES has it for around $119. USD

Triode also has an ST-70 "export power" version, as well.


The lower-cost approach is to find a 1KVA step down (and isolation) trannie, rather than one of the single winding "auto-transformer" type step-up / step down types.

SPecially made "universal" power trannies could be fairly costly, but the isolator / conversion trannies are common and relatively inexpensive.

Trafomatic could probably create one (if they don't already have it as a stock item) with 230VAC input, 115VAC output (this would would also translate to 240 in / 120 out).

I've seen various toroidal "isolation" trannies with four windings, basically two 120VAC inputs, which can be wired in series for 240VAC, and also two 120VAC secondaries, which could be connected in parallel for 120VAC, or brought out as two separate 120VAC windings. This type of transformer is fairly common, I'd go for the 1KVA version, (1000 Volt-Ampstotal capability) as it will run cooler and quieter (less vibration and mechanical 50Hz mechanical buzz / hum) . The extra VA capacity allows for running additional pieces of 120VAC equipment if needed, for your audiosystem.

I.ve used smaller, lower VA capacity versions for 120VAC input and 240VAC output, for generating relatively high-current B+ of 250VDC.

/ed B
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Postby kheper » Thu May 15, 2008 7:04 pm

You are overlooking the obvious.

The Antec 720V 450VA toroid. It is designed to work on both 115 and 230. The Antecs have dual 115V primaries.

http://www.antekinc.com/AN-4T360.pdf

$52 on ebay. Strangely, it is listed as 400VA.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... :IT&ih=024


CORRECTION: You would need a different Antec model for the MKIIIs.

http://www.antekinc.com/AN-4T400.pdf

or

http://www.antekinc.com/AN-4T450.pdf
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Postby kheper » Thu May 15, 2008 7:21 pm

Complete and utter overkill for 1 MKIII.

1600V CT 800VA toroid. $96.

http://cgi.ebay.com/1600V-CT-at-800VA-T ... m153.l1262

800V x 2 HT secondaries. You could do something with one of the 400 - 400 windings. With 1 A of current capacity, you could run 2 MKIIIs.
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