A powder spray coating discharge assembly (230, 260, 216, 228, 232) for connection to an electrostatic spray coating gun (210), the gun (210) having a gun body (212), means for connecting to a supply of coating powder and means for supplying a voltage (20) at first and second potentials respectively to first (292) and second electrical connections (294) each for connection to a respective one of a discharge electrode (232) and a counter electrode (260), the means for supplying the voltage (20) comprising: a variable voltage power supply (114) having an input connected to an electrical power source (110), an output connected to each of the first and second electrical connections (292, 294), a control circuit (128) for controlling the variable voltage power supply (20) and means (120) for sensing an output load, wherein the control circuit (128) is adapted to adjust the variable voltage power supply (20) to reduce the voltage and current in proportion to a sensed increase in load, or vice-versa.