Changing 120v AC to 240V

Bought a bit of audio gear from the US at a decent price even allowing for carriage. Guessed it might be 110v - but it is actually marked 120v 60Hz.
Looking inside, it has an analogue power supply - I was rather expecting an SMPS.
The transformer primary has two winding wired in parallel which seem to be coil 1 black start brown end, coil 2 red start orange end.
Red and black are paralleled as are brown and orange. Red/Black goes to neutral, brown/orange to the off/on switch.
So it looks like I may be lucky and simply altering them to series will do it for 240v. Link brown and red and 240 goes between black to orange? Does it matter if one winding has the connections reversed when they are in series?
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Yes, they'll cancel out!...
Have you got a VARIAC or similar to test it with before, close switch and retire to a safe distance?..
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tony sayer wrote:

    But the fuse will give you a chance!
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On Wed, 26 Feb 2014 18:05:03 +0000, tony sayer wrote:
<snip>

I use an incandescent light bulb in series with the mains. Cheap and cheerful. :) Keeps the magic smoke in place.
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scribeth thus

Both voltages are common in the USA. So it will be precisely for this pupose. (So there probably exists information somewhere (manufacturer/internet? Label inside somewhere/users manual) on how to change the voltage connections.
You commonly see a similar idea on three phase motors too.
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Not in the manual or on the maker's site. In common with so many these days they don't make a schematic available.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Yes, my house had both voltages (240 to run the washing machine/dryer) and a whole variety of different sockets.
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Tim

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On Thu, 27 Feb 2014 09:41:24 +0000

We lived in many houses in the US, and 240 volts was only ever provided for dryers or cookers. We never had any sockets (receptacles in American) wired for 240v except for those specific devices.
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wrote:

Sorry, my post was incomplete. I meant to say: " ... and a whole variety of different 120V sockets."
I had 2-pin, 2-pin-polarised, 3-pin, and I'm sure there must have been others. The US 3-pin socket and its flimsy accompanying plug is a PoS, given that for a given activity, twice the current is passing, hence four times the heat generated at the socket. The cable for anything using a lot of power, such as a fan heater, is huge.
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On Fri, 28 Feb 2014 15:04:33 +0000

Understood.

Totally agreed. And why they haven't caught on to the idea of putting a fuse in the plug, I have no idea. Most plugs there now are moulded onto the end of the cable.
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In theory, each US socket is on its own radial with its own circuit breaker.
UK fuse in the plug is to protect the flex (maximum 13 amp) as the circuit is capable of 30 amps or so.
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On 2/28/2014 10:55 AM, Dave Plowman (News) wrote:

Really? Each socket on its own radial? Radials, yes. Circuit breakers, yes. But apart from things like freezers, cookers, etc, quite a few sockets per radial.
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On Fri, 28 Feb 2014 11:11:27 -0500

Agreed. When we had some additional wiring done, it was because the existing CB couldn't handle both the microwave oven and the 'fridge together, and that circuit supplied the whole kitchen except for the 240v oven. There was one CB for each end of the house on each floor, making 4 CBs, including one for the single room upstairs.
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Guess it has to be because of the potential current draw.
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Tim

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Davey wrote:

        US Xmas lights have fused plugs.
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wrote:

And the notion of wiring one up yourself appears to be foreign. I had the devil's own job finding an ordinary 3-pin plug I could wire myself. And even then it was ugly as sin.
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On 27/02/2014 07:52, harryagain wrote:

Unlikely, me thinks. 240V in the states would be used for high power items that would otherwise draw too much current at 110/120V. This class of item wouldn't fall into that use category, 240V wouldn't necessarily be plumbed in at the environment of use (studio, lounge etc...).
More than likely the choice of transformer is commonly in international use. However the designer might not have sized the device for 50Hz use, even though the provided windings are configurable. And then there's other components. Ratings of capacitors, rectifiers, EMI filters and insulation / creepage distance.
So all that needs checking to be safe. You are right about consulting documentation.
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Adrian C wrote:

    As the product is described as 50/60Hz. It is very unlikely that two different transformer cores will be used. Also, 110/120V products have to withstand up to about 150V in operation because of the US distribution system of very long lines and the resulting poor regulation. I can't recall the exact voltage ranges we designed for in 120V PSUs, but I reckon it was 80 to 160V. My experience is that I've yet to see a US consumer transformer fail due to core saturaton at 50Hz. I generally buy US ceiling fans for summer use and none of these have yet shown any signs of overheating.
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It's pretty easy to get a 110v transformer to run US equipment here. If it really were a problem with transformer design on the average low power device I'd have thought it would be known.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Or put a light bulb into the circuit.
Brown to red and the others to mains via switch, I'd suggest. Brian
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