Actually the very early V-3's had adjustable transformers. Later ones changed to a single-voltage transformer. It's easy to tell which one you have. Look at the Serial Number on the back of the unit it will begin with a "1", then a letter, and then 4 numbers. If second character is "K" or below, then the voltage is adjustable. If the second character is "L" or higher, then the voltage is not adjustable. If you have an adjustable voltage version, call Michael at 303-442-7300 x223 and he can fax instruction on changing the voltage. Choices are 100, 120, 220, 230, and 240 VAC.