Have 150W 4300K ARCADIA (Pendant) MH Lighting. Problem is: 1) sometimes the light would go off and comes back say 30 mins. later. I was told that MH is very sensitive to changes in voltage. A slight drop in voltage would shut off the light. Is this true? 2) the ballast sometimes hum, but now it has stop. Now it's the pendant's turn to give a very annoying hum. How can this be rectified?