Abstract: A powder coating spray gun includes a high voltage generator with a transformer and voltage multiplier circuitry located within the handle and barrel portions of the gun. The voltage multiplier circuitry includes a number of stages of capacitors and diodes. In the event of failure of the voltage multiplier, backup or secondary circuitry may be selected by the user by removing the barrel of the spray gun from the handle, rotating the barrel to a second position, and re-inserting the barrel into the handle. The secondary circuitry can include a duplicate capacitor for the first stage of the voltage multiplier. A first and second set of connecting pins in the barrel of the spray gun couple the voltage multiplier circuitry with the transformer. The connecting pins are received at active sockets and inactive openings in the handle portion of the spray gun.