Bshappered, your VPI has a synchronous motor I beleive. That means it should sync up with the 60 cycles from an outlet. The 60 cycles is almost always accurate. The voltage will vary a lot in some places, but not the 60 cycles. You could check the outlet voltage with a multimeter. Read the instructions, and be careful. You could also get a P3 Kilowatt meter that just plugs in. Your voltage could be from 114 volts to 126 volts. With that voltage variation, the VPI should hold its speed. Something else must be going on, unless you really have voltage out of the 114-126 volt range. The 60 cycles will keep it right with 114-126 volts. A link for a P3 Kilowatt, that might be sold at your local home center. [http://www.mcmelectronics.com/product/28-10985&CAWELAID=220321019]