The general case (always) is that when a transformer stops working the solution is to replace it. It would be extremely difficult to "fix" a transformer.
Transformers can be remarkably cheap if you buy them from the right place. All you need to do is to match the Output (secondary) voltage and have a power rating (Wattage) the same as or more than the one it replaces.
A person handy with a soldering iron could easily manage the job
Good luck...
Peccavi, July 2013
