Without measures and without schematics, I think it will be very difficult to make a diagnosis.
The only possibility is to do reverse engineering.
the 4 transformers that are chained to give 220v
Are they wired in serie ? What is the output voltage of each of those dc/dc converters ?
Be careful, there is high dc voltage in such a converter, don't try to repair it if you are not an electrician or an electronics engineer qualified to work with power electronics.