Old US test equipment use in UK

[ppppenguin]

The problem, that you're probably aware of, is frequency. A transformer designed for 60Hz will saturate more easily at 50Hz. US mains is nominally 120V so running at 110V will help. But measure to make sure it is 110V or less. You can measure if a transformer is going into saturation using a variac and ammeter. Ideally take all load off the transformer under test. Often done by unplugging all valves. Wind up the voltage and see when the current suddenly starts to increase. This may take some judgement as some transformers will enter saturation more suddently than others.