Chaning transformer wiring from USA to UK mains

[A Sanchez]

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

 

[AndrewT]

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.

 

[A Sanchez]

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

 

[AndrewT]

Hi,
a cap across the mains leads must be X rated @ 275Vac.

 

[A Sanchez]

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