Hi guys, I have a step down transformer that was connected to a 110V/220V voltage selector switch. I need to connect it to 220V but am unsure how to correctly identify what wire needs to connect to what and there are no markings on the transformer at all. I have 155ohms resistance across the red pair and 155ohms across the blue pair. Cheers!

 

The two windings in series, it appears the two centre tapped would be coupled together and the outer red and blue used for 220v.
Max.

 

The two windings in series, it appears the two centre tapped would be coupled together and the outer red and blue used for 220v.
Max.

Like so?

 

Yes.
Do you have a 120v source, by any chance?
You are not using a socket for a entry are you?
Max.

 

I don't whys that?

 

If you have a source of 120v you could easily confirm the right combination.
Max.

 

Ah yeah fair shout. All sorted now, correct voltage at the output and no bangs, cheers mate!