Yikes! Yes Tom I would say that is the case. Larry Pina describes it in some detail. In order to use 220v you MUST have the 240v power supply. There were two models of the 128k/512k, one contained the international 240v power supply and the other contained the 120v. If you have the latter, there is no way to convert it to 220v without adding extra parts and I'm not even sure it could be done without modifying the 120v analogue board. If you have the 240v "International" marked clearly on the vinyl jacket, then you might be able to change the circuit to accept 120v since it was designed to be convertible. But that is not what you want to do. If you find you have a 220v international power supply in your Mac, but are currently using it as a 120v, then yes, you should be able to easily change something to switch it back to 240v. That is the most likely reference I can think you may be referring to having seen around the internet.