Good Morning

I found that the transformer of my rechargeable battery charger was not giving voltage, my question is, can I change an internal transformer with an external power supply?

I would appreciate your help.

Good Day

Info:

Input: 100 - 240 V CA 50/60 Hz 2.5 W
Output: 2.4V 200mA CC (battery AA) x2.4V CC 200mA (battery AAA) x2

This is circuit:

 

Are you sure the transformer is the cause of your problem? The circuit connected to the secondary winding could be faulty and loading down the output from the transformer.

 

Yes, I was measuring the resistance of the transformer connectors with a multimeter and it marked 0, however, in the other components if it gave measurement

 

The resistance of the secondary winding is supposed to be very low. The transformer is the least likely thing to be causing your problem. What is the resistance of the primary winding?
To answer your question: NO!
What voltage would you use for an external supply and where would you connect it? There is not a circuit diagram available for this device so we have no Idea what the voltages and frequencies are in any part of the circuit.