Chaning transformer wiring from USA to UK mains - diyAudio
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Old 30th May 2008, 03:47 PM   #1
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Location: Brooklyn, NY
Default Chaning transformer wiring from USA to UK mains

Hi,

I brought my preamp from the USA to the UK and I have been using it with a step up transformer, which is horribly noisy, and I would like to eliminate it.

I have opened the preamp and found that it has a pcb mounted transformer with four primary and four secondary points.

On the primary side 1-2 and 3-4 are connected and then on the secondary side 1 and 4 go to preamp and 2 and 3 are not in use.

Can I assume that this is a dual primary 115-0 115-0 trafo where the current USA configuration is:

1-2 115-115
3-4 0-0

and if the above is the case change bridging as shown below to make it UK ready:

1 115
2-3 0-115
4 0

I would like to post a drawing of the current physical connections and the proposed change but I do not know how to. I could e-mail it to anyone if that could be of any help.

Many thanks

Antonio
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Old 30th May 2008, 03:55 PM   #2
AndrewT is online now AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
hi,
remove mains connection from 2 & 3.
link 2 & 3.
fit a mains light bulb in series with the primary.
stand back and switch on.
If the bulb lights, then 2 & 3 were wrong.
If it stays off, then check your transformer secondary voltage.
If OK, then remove the light bulb and you have a 230Vac powered pre-amp.
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regards Andrew T.
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Old 30th May 2008, 04:19 PM   #3
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Location: Brooklyn, NY
Andrew,

Thanks again.

I will do as you are suggesting.

I forgot to mention that there is a small capacitor before the transformer in between the mains leads. Will I have to change this capacitor due to the new Vac ?

Regards

Antonio
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Old 30th May 2008, 04:49 PM   #4
AndrewT is online now AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Hi,
a cap across the mains leads must be X rated @ 275Vac.
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regards Andrew T.
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Old 3rd June 2008, 10:37 PM   #5
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Location: Brooklyn, NY
Andrew,

It all worked fine. I made the changes and tested with light bulb.

Now I have a 230Vac power noiseless preamp!

Thanks again!

Antonio
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