I own the M5400-PM. I have observed that if all my equipment (attached to the M5400-PM) is turned off, the output voltage will drop to 114-115V. When I turn on the equipment...the output voltage will display 123V-125V. The input voltage stays steady at 125 volts. What is happening here? Is this normal? I am within my 30day return policy at BestBuy....should I get another unit?