Hi David.
The 42V sounds like the model of the printer, not the cash register. Can you have a better look and see if you can find any more details about your machine? It is VERY rare for a transformer to fail. How do you know it's that?
Best thing to do is to visit www.eposwizard.co.uk and send me a personal message (I'm NZtech on that site) with a model number or a photo of your machine, and I may be able to help.
Mark, June 2008