Question about transformer

[goldkenn]

I have a big R-core transformer which would like to use to built a chip amp.

However, the transformer is dual secondary 4 wires type, just know 2 blue wires is one set 25V and 2 green wires is another set of 25V, without labelling which wire is 0V, which is 25V.

If I use it as a 3 wires secondary with single bridge rectifier (a very high quality ready made PSU board which I don't want to cut or change anything), as from my understanding, I will need to short one blue 0V and one green 25V together as center tap, am I right?

So how to find out which of blues/greens is 0V and 25V?

Or if just simply connect any one blue/green together as the center tap, then test the voltage as trial, in general, will the transformer demage if I am actually short the two 0V or two 25V together?

[pacificblue]

Originally posted by goldkenn
Or if just simply connect any one blue/green together as the center tap, then test the voltage as trial, in general, will the transformer demage if I am actually short the two 0V or two 25V together?

Exactly the correct way of doing it. No damage will ocurr.

[AndrewT]

first connect all the transformer wires to individual terminals on a terminal strip.
Connect the mains through a light bulb tester.
Now measure the output voltage of each secondary.
Now add a temporary link from one green terminal to one blue terminal. Measure the voltage between the other two green and blue terminals. It will either read 0Vac or double volts ac.
If it reads zero then swap the link to the other blue terminal. and remeasure the output voltage.
Now you can remove the light bulb tester. But you will need it again as soon as you add anything to the transformer.

This procedure will save your transformer from damage, it will save you from damage, it will save you repeatedly blowing fuses.

[goldkenn]

Thank you!!