10-22-2014, 11:15 AM
I remember the first time, about 15 years ago, that I calibrated my 600A. Some voltage readings were close and others were way off. It was very confusing at the time as I found the tester was reading correctly when I tested the same tubes on a friends 600A. I called the person across country who had calibrated, and sold my friend his tester. He told me to use the correct meter and with it I found all readings were correct.