Halogen lamp electronic transformer not working

I have 220 volt AC to 12 Volt electronic transformer. It doesn't give any out put 12 Volt AC. Both 12 v output phase and neutral wires are getting phase supply.
May I know what is the problem?

I'm not sure what you mean by "output phase and neutral" The output of these "transformers" is floating so neither output wire is connected to earth in the same way as mains neutral is connected to earth as the sub station. If your testing was done with high impedance meter then there would probably be enough capacitance coupling between the input and output to give a reading. But I would expect the reading to be less than full phase to neutral voltage.
These transformers are so cheap it is not worth the effort repairing them.

Les.

I have several 400 watt lights that are 120 vac I have never checked the transformer voltage but every time a light stops working it was always a bad capacitor. Replacement caps can be equal or greater value but never smaller.