Bringing up a old Powersupply

I can't help with your general question, but I do have a safety tip. If that power supply is a Variac or similar device, it is an autotransformer. This means that it does not have separate primary and secondary windings. So don't count on it to provide the electrical isolation that you expect from normal transformers. If you need to probe the line-voltage side of the power supply with an oscilliscope, for instance, make sure that you also use an isolation transformer on the input side of the Variac. I don't want to start yet another discussion on the supposed merits of floating scopes. An isolation transformer for the UUT is the correct way to do this. Of course, for this to work you must NOT plug the scope into the same isolation transformer as the UUT.