Do you have any sort of precision, regulated, adjustable lab bench power supply that you could use to vary input voltage? If not, using a potentiometer as you mentioned would also work.
Also, how many of these did you buy? If it's something like a dozen, manual testing will be practical. If it's something like a hundred, then automating the testing might be a good idea, and a fun project all by itself if that sort of thing interests you. -- Mark J. Blair, NF6X <[email protected]> http://www.nf6x.net/
